WileECoyoteSr

I'm sorry. But I'm going to give you guys the whole "nine yards" because I see a lot of incomplete posts asking for help. Here is what I've got so far.
1991 Chevrolet Camaro Z-28 Coupe.
VIN 1G1FP2387ML117283, Mileage: 282530 miles on chassis. Supposedly 85,000 miles on original rebuilt 5.7L L98 TPI engine, 65,000 miles on 700R4 transmission. All systems on the car look to be original configuration and unmodified. Help me please!
T.W. Anderson, txt or call 316-641-6266 or email twanderson1@***.net.

CRANKS WITH FUEL PRESSURE TO INJECTOR RAIL BUT WON’T START. DOESN’T EVEN TRY TO FIRE BECAUSE IT SEEMS TO NOT GET ANY FUEL. WILL START IF YOU SPRAY STARTING FLUID DOWN THROAT BUT WON’T REMAIN RUNNING. SUSPECT INJECTORS NOT FIRING.

I was advised by a friend’s friend in the Corvette club to check the following:
Ck the computer grounds are clean. – The ECM is plastic shock mounted and does not have a case ground. Grounding is via the wire looms and connectors which I did check.

Ck fuel pump relay operates. Should come on for 2 seconds when key is first on. - It is, and does.

Ck faulty in tank fuel pump check valve. Faulty valve allows fuel to drain back to tank. – It was my understanding that it is standard for the fuel pressure developed by turning the key on, but not starting the car, will bleed off eventually. In any case, fuel pressure at the fuel rail for prime and crank seem to be within specs.

Ck both fuel injector fuses are intact – visually checked both fuses.
Ck all connections to fuel injectors, coil, distributor for shorts to ground – done.
Ck ECM is sending signal to injectors. – I don’t know how to do this other than the 12 v test with key on, not cranking.

Here’s my story and what I’ve done so far.

Previous owner purchased the car 10/2008 but didn’t license it until 4/2009. Traded with me for a S10 4x4 pickup early 8/2009. Seller and his wife stated that they only put 300 miles on the car in the 3 months since licensing it because seller got it for his wife but she didn’t like sitting so low. She was use to 4x4 pickups.

Seller stated that twice during those three months he went out to the car to start it to go to lunch and it would turn over but not fire. Yet when he went out that evening to go home from work the car started both times.

I’ve owned the car for about a month. I haven’t modified it and have spent the time replacing burnt out light bulbs, cleaning the car and detailing it. I DID disarm the SRS airbag system and removed the indicator light since that light was indicating that one of the six sensors for the system was defective. The SRS is completely disarmed and will remain so.

All systems worked on the car although it idled slow when in gear with the A/C on. Automatic system did not adjust idle speed up to compensate for extra drag on engine.

After I power washed the engine the cruise control would not work again. I have been unable to find any wires off any connections in the engine bay.

We drove the car for two weekends extensively and put 124 miles on the car the most recent weekend with many stops and restarts. We had no problem other than when hot the starter turns the engine over slightly slower than desirable indicating to me that the starter will no doubt have to be replaced soon.

Friday night (8/28) we parked the car at the car show gathering at West St and Central for the evening and when departing the lot it started normally. We cruise around for about an hour and then put the car in the garage. Sunday (8/30) I went out in the afternoon to start the car to take it to a relatives and it exhibited the problem it now has.

The car will spin over with the starter faster than it normally did when it usually started. But it will not fire. It will fire if you spray Starting fluid down the intake throat.

What I have done to try to diagnose and fix the Camaro engine
First, I’ve research everything I can on the internet. The most helpful has been Third Generation Camaros at https://www.thirdgen.org/forums/ but several other owners have had the same symptom and no one fix was the answer. One was an oil pressure sensor. Another was an ECM. Etc.

Since the fuel pump can be heard priming the fuel system when first turning the key on but not starting the car, I assumed there was fuel to the engine and instead started with the electrical system. I could not see a spark from either the coil wire or the #1 cylinder wire when trying to just partially ground out the wire with a screwdriver and so I assumed (in error it turns out) that the engine lacked spark. I replaced the coil pack and still no spark. I replace the Ignition Module and still no spark.

At that point I was reviewing comments on the 3rd Gen. forum and found similar circumstances and the posting member was advised to try starting the car with starting fluid. I did the same and the car will fire until it uses up the starting fluid and therefore I DO HAVE SPARK. I got no fuel.

I started checking the fuel system. I had pressure at the fuel rail as evidenced by pushing the valve stem on the valve that allows you to attached a pressure sensor. So I put a fuel injection pressure gauge on that connection and found that turning the car on, but not cranking gives an initial 44 lbs of pressure that slowly dies off. Cranking gives a constant 41 lbs of pressure.

The forum suggested checking the injectors then since fuel was being fed to the injector connection. It was suggested I check the left bank and right bank with a NOID LIGHT. I did so and got no light from either side.

The forum suggested if no light at the injector connection the ECM may be dead even past the limp in mode. I obtained a used ECM from a salvage yard, swapped over my PROM from the original equipment, and cranked the car. No fuel to the cylinders, no start. Using the advice of the forum I tested both wires to the injector at #1 and found both had 12v with key on, not cranking. I put the original ECM back in the car with the correct original PROM and duplicated that the injector was being fed 12v with key on. I DID NOT ATTEMPT TO READ THE VOLTAGE WHILE CRANKING.

What I have NOT done yet but have been advised by the forum to try:

VAT – Vehicle Anti-Theft – Some cases of messed up ignition key wiring have been experienced. Forum is suggesting disabling the VAT by one of several methods presented. No way of checking the VAT was given since some faults will still give the security light extinguishing yet will disable the fuel injection circuit.

CTS – Coolant Temperature Sensor – is another sensor that if defective may think the car is overheated and will therefore tell the computer to shut off the fuel.

TPS – Throttle Position Sensor – if defective will tell the computer that the throttle if fully open which then signals the computer to turn off the fuel.

OPS – Oil Pressure Sensor – if defective tells the engine it isn’t safe to run with low oil pressure and shuts off the fuel.

WHAT ELSE COULD BE TELLING THE FUEL INJECTORS NOT TO FIRE?
T.W. Anderson, txt or call 316-641-6266 or email twanderson1@***.net.

Option List for this 1991 Z-28 Camaro:
ACS: ADJUSTER, FRT ST, POWER, 6 WAY, BKT, DRIVER
AJ3: RESTRAINT SYSTEM, FRT SEAT, INFLATABLE, DRIVER
AM9: SEAT, RR, SPLIT, BACK, FLDG
AR9: SEAT, FRT BKT, EUROPEAN STYLE, PASS A DRIVER RECL
AU3: LOCK CONTROL, SIDE DR, ELEC
A31: WINDOW, POWER OPERATED, SIDE
A90: LOCK CONTROL, RR COMPT LID, REM CONT ELEC RELEASE
B18: ORNAMENTATION, INTR, DELUX
B2L: PERFORMANCE PACKAGE & ENGINE PACKAGE V8 5.7LPFI
B34: COVERING, FRT FLOOR MATS CARPETED INSERT
B35: COVERING, REAR, FLOOR MATS CARPETED INSERT
B84: ORNAMENTATION, EXTR MLDG, BODY SIDE
C49: DEFOGGER, RR WINDOW, ELECTRIC
C60: HVAC SYSTEM, AIR CONDITIONER FRT MAN CONTROLS
DC4: MIRROR I/S, R/V, TILT, DUAL READING LAMPS
DG7: MIRROR 0/S, LH & RH, REM CONT, ELEC, PAINTED
D34: MIRROR, VISOR VANITY
D42: SHADE, RR COMPT SECURITY
D5X: GEAR, SPEEDO DRIVEN
D8F: SENSOR, VEH SPD
D81: SPOILER, RR, AERO WING
E5Z: SPEEDOMETER ADAPTER (DELETE)
E9Z: SPEEDOMETER KEY (DELETE)
FE2: SUSPENSION SYSTEM, RIDE HANDLING
GU5: AXLE REAR, 3.23 RATIO
G80: AXLE POSITRACTION, LIMITED SLIP
G92: AXLE REAR RATIO, PERFORMANCE
IPC: TRIM- INTERIOR DESIGN
J65: BRAKE SYSTEM, PWR, FRT & RR DISC
KC4: COOLING SYSTEM, ENG OIL
K34: CRUISE CONTROL, AUTOMATIC, ELECTRONIC
K68: GENERATOR, 105 AMP
L98: 5.7 LITER V8 TPI ENGINE
MD8: TRANSMISSION, AUTO 4 SPD, THM 700 R4
MXO: MERCHANDISED, TRANS, AUTO PROVISIONS, O/D
NA5: EMISSION SYSTEM, FEDERAL, TIER O
NP5: LEATHER WRAPPED, STEERING WHEEL AND SHIFT ****
N10: EXHAUST SYSTEM DUAL
N64: WHEEL & TIRE.SPARE, SPACE SAVER, ALUMINUM
N96: WHEEL, 16X8, CAST ALUMINUM
QLC: TIRE ALL, P245/50ZR16/N BL R/PE ST TL HW4
T96: LAMP, FOG
UB3: CLUSTER, INST, OIL, COOL TEMP, VOLTS, TRIP ODOM, TACH
UN6: RADIO, AM/FM STEREO, SEEK/SCAN, AUTO REV MUSIC
UQ1: RADIO PROVISIONS, FOR STEREO
U79: SPEAKER SYSTEM, 4, DUAL FRT COAX, DUAL EXT RGE PKG
VAN: ASSEMBLY PLANT, VAN NUYS, CA
VK3: LICENSE PLATE, FRT MOUNTING PKG
V73: ANTENNA, FIXED
Z28: MERCHANDISED PKG, SPECIAL PERFORMANCE
1SD: OPTION PACKAGE 04
10Q: MOLDING COLOR , ARCTIC WHITE (91)
10U: PRIMARY COLOR , EXTERIOR, ARCTIC WHITE (91)
11P: WHEEL COLOR, PINK (92)
6ZW: SPRING, COMPUTER SELECTED, FRONT, LEFT HAND
7ZW: SPRING, COMPUTER SELECTED, FRONT, RIGHT HAND
8NL: SPRING, COMPUTER SELECTED, REAR, RIGHT HAND
82I: INTERIOR TRIM, MED DK GRAY (91)
829: SEAT BELT COLOR, MED DK GRAY (91)
9NL: COMPUTER SELECTED REAR RIGHTHAND SPRING
82C: TRIM COMBINATION, CLOTH, MED DK GRAY (C) (91)

Rolling Thunder

Well i must say that is a quite detailed post. I must say though like you said there are many posts for help that dont even have basic information. So i must commend you on your level of detail. Now on to the real problem. First we need to determine exactly what is not happening. Not i think its safe to say that it is a problem with the absence of fuel seeing as how it will start on starter fluid. Because your car is a VATS equipped vehicle I suspect that this is your problem as it will do just as you have described if failed. TO test this we need to either confirm weather or not you have the fuel injector pulse at your injectors from the ECM. I suspect you will not but to test this its as simple as doing the following:

1. With a 12 V test light: clip the ground lead to ground and touch the other end to the pink wire with a black stripe on your fuel injector. You should see the light turn on indicating the injectors are getting power.

2. Next with the test lights still clipped to ground put the probe onto the dark green wire on the fuel injector and have a friend try and start the car. You should see the test light flash if not you are getting no injector pulse.

Try it out and let us know how it goes.

topfile

I suppose you've seen my thread?

https://www.thirdgen.org/forums/tech...cranks-no.html

My biggest problem is the Car is 180miles away not in the drive way.

Look here
https://www.thirdgen.org/vats_passkey_system

Tell me.. is your security light coming on solid and staying on, exactly what does it do?

After waiting 4 minutes mine will not set the Security Light on the first crank attemp
as in no Security light at all. However, on the second attemp the Security Light comes on and stays on until the key is removed. This isn't correct and indicates VATS.

Yours Cranks but won't fire the injectors like mine.

Normal operation as I understand is that it comes on for 3 to 4 seconds in the KOEO
position then goes off..... Car Starts.

I've got a Computer Safe Automotive Logic Probe for $7.00 at Harbor Frieght Tools
item #98709. I hoping that will allow me to confirm a 30hz square wave going to the ECM from the VATS Module. The LED in the probe should flash rapidly if it is.
This signal tells the ECM it's OK to turn on the Injectors. The VATS module also
enables the Start Relay and controls the Security Light in the Cluster. My Start relay is bypassed I suspect.

I know tommorrow and will be able to post here again Saturday.

Rolling Thunder

Well i haven't read your post as i usually don't bother with posts that have got a fair amount of responses however i would like to point out a fer things to you that might be of service to you. First I think your on the right track. The VATS system as you know is a 2 part attack stop the motor from cranking and stop the injectors from firing. If your security light comes on if im not mistaken it should have disabled the starter (unless someone has messed with the system). If this is the case im already suspecting a bad VATS module. However rather than throw parts at it till it works there are things we should confirm first. Because this is a VATS issue lets make some tests at the heart of the problem, the VATS module itself. First Lets make sure the VATS module has a good connection to read the ignition keys resistance. With the key in place set in the run position (car not running) measure the resistance across the white and black wire and the purple and white wire. You should measure the keys resistance. If not you have a bad connection or a broken wire. If you do measure the correct resistance we can move on. Next confirm you are getting power to your VATS module by measuring the orange and pink and black wire to ground both should read 12V again with the key in the run position. Also measure to see if you have a good ground by measuring the resistance to ground of your black and white wire it should read near 0 ohms. If this is all true we can again move on. Next still with the key in the run position measure the yellow and black wire voltage to ground it should be 0V. If not the VATS module is not enabling the starter relay. If the VATS lite is on however you should read 12 V on the yellow and black wire. Lastly the 30 HZ waveform to the ECM needs to be checked. Unfortunately with a test light you will not likely be able to see it. 30 HZ means it cycles on and off 30 times a second which is pretty quick too quick for lights to even react (especially incandescent bulbs because by the time they cool down and stop emitting light they have already been turned back on again). This means youll likely see the light as just being on maybe a little dimmer than normal but appearing as just "on". To test this accurateness this youll need an oscilloscope or a digital volt meter that can measure frequency. It is also important to note that you dont want to just disconnect the VATS module and measure for this signal on the dark blue wire because the way it works is the ECM supplys 12v and the VATs modual shorts it to ground so its actually "sinking" a 30HZ signal not sourcing it. This means you need to leave it all connected to do that test. Sorry for the long post i know i just threw a lot at you but i figure being 180 miles away any time you do get on the car will be valuable and need to make the best use of that time rather than posting back and forth figuring out what to do next. If you have any questions about any of this feel free to send me a PM so we dont clog up this gentleman thread.

topfile

I hoping my experience may help fix your car.

My problem turned out to be VATS (Vehicle Anti-Theft System).

It was the portion of the VATS that measure the Key's imbedded resistor chip. As
with many others here, one of the two wires running up into the steering column was open.

Therefore the key could not be read. Therefore the ECM would not allow the car to start.

Previously my first start attempt set no Security light on the dash no matter what
key I used. I believe because VATS didn't know a key was in the ignition due to the
broken wire mentioned above. Once I bypassed the key measuring circuit of VATS
the Security Light turned on with my first attempt to start. The light didn't go off
as I expected in the KOEO position even after waiting 10 plus seconds. However, the
Security light did go off once I moved to the Cranking position and it STARTED!

My key chip measures 3.00K ohms using my VOM meter. I simply choose two resistors
valued at 1.5K ohms and connected them in series to give me a value of 3.00K. Then,
after finding and unplugging the two wire connector (which employs two small thin
white jacketed wires incased in a bright ORANGE outer jacket) above the drivers feet.
I plugged in the two series resistors in the back of the two pin male connector,
running towards the VATS module away from the column, for a quick test.

Once I determined this was the Fix, I made it more permanent by clipping the small
white wires going up towards the Steering Column. The female side of the connector
then dropped to the floorboard. Then I soldered my 3.00K ohm resistor network into
the two remaining wires of the female connector and covered it with black silicon.

Once dried, I plugged this new more durable network back into the Male connector
end. This 3.00K resistor network became a substitute for the Key chip resistor. Thus
my VATS sees a key at all times.

As I suspected, my Starter Enable Relay was inadvertently bypassed by a previous
effort of a earlier owner. So my Starter would crank but the Fuel Injectors would not
activate.

It's all good now!

Hope this helps.

WileECoyoteSr

I want to thank all those who have posted.

WileECoyoteSr

I want to thank all those who have posted. I replaced the ECM and that didn't work. I priced out a salvage steering column since my multi-function switch won't go to brights so I figured I swap the whole thing and defeat the VATS.

But in the meantime, I don't give up easily and since the car miraculously healed itself twice for the previous owner I kept hoping and turning the key on it. Like I’ve done every day this week I went out to the garage to start it and it just cranked with no firing. I figured it was time to call AAA and have it towed someplace although I didn’t know where. So I pushed it out of the garage. While pushing it, it reminded me of when I put the 85 Corvette TPI motor in my 61 Impala. That transplant had every sensor brand new and it wouldn’t start. I cranked forever on it. Finally I got fed up and tried starter fluid. It fired. So I had one of my sons carefully feed it starter fluid while I tried to keep it running and low and behold, after about five seconds the computer took over and it ran like a top from that day on until I sold the car a year later.

With the Camaro on the driveway and nothing to lose but an insurance claim, I took the snorkel off the intake, saturated the intake with starter fluid, waited a few seconds for the fumes in the engine compartment to dissipate so I wouldn't have a flash back fire and cranked it with about a quarter throttle fed in. It fired AND RAN at 2,000 RPM! It even idled at the correct cold idle speed after I let it warm up a bit and finally got the guts to let off the accelerator.

What could it have been? I’m betting it was the Oil Pressure Sensor. I had not changed that yet so the same one is still unchanged on the car from when it refused to fire. But whoever rebuilt the motor on the car 81,000 miles ago didn’t put in a new oil pump, evidently, because at 450 rpm idle (ICV needs replacement) it drops down to 20 lbs. Not low enough to rattle, but low enough to concern me. Give it 1,000 rpm and its at better than 30 lbs. I’m betting that when I shut it down the last time it was driven it was at the minimum pressure value for the Oil Pressure Sensor and if I hadn’t turned off the key, the computer would have killed the engine.

When I forced it to run on starting fluid and let it jump to 2,000 rpm upon start up, I’m betting the Oil Pressure Sensor reset or said OKAY to the computer and allowed the computer to put the injectors back on line. That’s the only thing I can guess. Maybe one of you Techs can confirm or deny that.

Of course now the problem isn’t as easy as replacing the Oil Pressure Sensor. It’s doing its job. It’s the oil pump that is slacking off. And I haven’t looked under the car but I’m betting it’s a bear to get the pan off and get at the pump. I may try running 40 weight oil in her to see if that will keep the pressure in an acceptable range. That worked on my 72 Z-28 Camaro with the factory performance 350 years ago. I might also try to coax the idle to stay higher.


Update as of yesterday afternoon: The Idle Control Valve was stuck. I removed it and soaked the mechanical end in lacquer thinner and brushed it with an old toothbrush. I did NOT attempt to change the pressure rods length per cautions I've read on 3rd Gen. After it was as clean as possible I reinstalled it and starting the car it idled back at the 450 rpm minimum. That is until I revved it and held it at 2,000 and generally disturbed the neighbors with the sound of the pipes growling. After about ten minutes of abuse the ICV is working as per spec. AC on higher rpm, watch it drop with AC off. In gear, out of gear. Amazing. And Oil pressure remains in the high 20's to low 30's lbs range with proper idle speed.


We drove her for an hour on Thursday night when I first got her to run again. Started and stopped five times. Did the same thing last night, and she's being well behaved and even idles now. Thank God! Because I'm out of a job and this is supposed to be our no-payments car while I dump my Hybrid Civic and its payments and look for another management job here in doodah (Wichita) or wherever.


Thanks again to all who had counsel for me and the others. And I'm still going to keep that VATS info in mind if it acts up now since I've got fair oil pressure.

WileECoyoteSr

I say again GRRRR! Maybe I should have a GTO. Sorry. Weak moment. The Camaro did it to me again. Spent a nice evening with my wife cruising around. Stopped and started a number of times. Nothing to make her overheat. The car. Keep it clean guys. Took them both home and all is well.

Two days later I go out to run an errand in the Camaro and it spins over like a top, makes 30+ lbs of oil pressure just spinning the starter, but no fire in her belly. I called my wife out to the garage to run the starter while I spray starting fluid down the intake and manipulate the throttle. She started right up and idled perfectly.

My wife's words were "if it's not reliable I'm not driving it. And since the purpose of getting it (the Camaro) was to allow you (me, Wile) to use my (her) Jeep for going out of town to look for work, you had better sell it!" I don't want to. It's cheap fun (so far). But I have got to get this failure to start fixed.

TELL ME: The Oil Pressure Sensor is designed to shut off the fuel (but supposedly turn off the starter as well??? It doesn't!) when oil pressure is below specs. Does it do so by creating an "Open" when pressure is low? Or does it create a "closed" circuit when the pressure is low? I'm thinking if it fails to open, and if I disconnect and jumper the sensor loom wires, I can test drive the car for a while in that configuration to determine either true oil pressure, or Oil Pressure Sensor reading causes a fault.

Same question for the Coolant Temperature Sensor. Does it tell the computer that the engine is too hot by "open" circuit, or by completing a "closed" circuit?

In the meantime I think I'll give her 10W-40, or 20W-40 if I can find it. It helped my 72 Z-28. And being in Wichita, Kansas I don't think it would hurt.

WileECoyoteSr

I was just over on a Corvette forum to see what they have to say and I noticed they talk about some L98 engines having an Oil Pressure Sensor on the side of the head, and an Oil Pressure SWITCH back by the distributor. Do our 3rd Gen Camaro L98's have that SWITCH and is that what I need to replace to try to further diagnose this failure to start problem????

Don't let me confuse you all. I've learned since this posting that the Corvette does in deed have two oil pressure sensors. One is for the gauge, the other for the go/no go input to the computer. Or at least that's the lay versions. Our 3rd Gen. Camaro L98 TPI according to sources who have contacted me do NOT have two sensors. Just the one on the left side of the block.

topfile

OK, sorry that happened to ya.

Check out this schematic of your 91Z 5.7L, click it to magnify.....
http://www.austinthirdgen.org/mkport...ine_wiring.gif

Notice the Fuel Pump/ OIL pressure Switch top center of the circuit.


I think your's is good and that's the only reason the Camaro runs after you
start it with Starter fliud. Let me explain......


What I understand is after 3psi of oil presure is established this switch
activates to supply power to your fuel pump in the tank (Fuel Tank Unit
sch. reference). However, before this occurs you hear the Fuel Pump
prime with the key on for a few seconds and stops. This is because the
Fuel Pump relay was activated to prime the the pump for starting. Once
accomplished the ECM turns the relay off to the resting position shown in
the Schematic. When you actually start the engine oil presure is
established and the Fuel Pump/Oil Pressure Switch turns on and runs your
Fuel Pump.


If the Fuel Pump/Oil Pressure Switch was bad your car may start but it
wouldn't run for long.


If However, your Fuel didn't prime then the car wouldn't start except with
starter fliud and then run only until Oil Pressure was established and the
fuel pump was activated.


Diagnosis: Intermittant Fuel Pump Relay contact or related wiring.

That really sounds doesn't it? I hope it's right may someone here could
confirm.

topfile

Try That again...

That really sounds good doesn't it? I hope it's right maybe someone here could
confirm.

WileECoyoteSr

TopFile - sounds logical to me. Let me think about it and perhaps I'll track down a fuel pump relay Tuesday. Wiring is tight and undamaged. All appears normal but we know it isn't.

I really appreciate your analysis. But I'd also invite any other comments or theories members might have. Anyone actually experienced this occassional "failure to launch" and truly resolved it????

Chevy8588

iTrader: (1)

VATS.... I had a VERY similar problem on my cadillac, over time the contacts in your ignition wear out and may not read the key. as far as i know the car will crank but the injectors are shut off by the ECM. measure your resistance in your Key pellet and bypass your Vats with an appropriate resister, $.50 fix for a $500 problem.

WileECoyoteSr

Chevy 8588 I'm really disappointed. My VATS bypass cost me $2 plus tax instead of 50 cents because Radio Shack made me buy five packs of the resistors. The good news is that the bypass is as easy to construct and install as the several descriptions on this site have provided.

THE BAD NEWS IS IT DIDN'T DO A !@#$%^&* thing to resolve the "failure to launch" problem. But at least I've checked that fault off the list of possibles.

Still would not start with bypass installed. But as before it does start if I load the intake with Starting Fluid and get it to fire up around 2,000 rpm.

I appreciate the comments on the Fuel Relay. But they seem to run to prime. Then they'll run during the engine run. And you hear them shut down just seconds after key off. Besides, which one of the three relays on the firewall aft of the brake master cylinder is the Fuel Relay?

I think my next step will be to purchase and replace the Oil Pressure Sensor/Switch. I found where the Corvettes have two separate oil pressure devices on their L98 and that confused me a little. I thought Chiltons might be missing one of ours. One on the Corvette is a sensor for ECM / Instrument read out. The other is a switch for the ECM go/no go input. Our 3rd Gen Camaros (at least 91 TPI) apparently only have the one on the left side of the block.

I can't believe that the gauge will register 30 lbs pressure cold cranking during my failure to launch episodes and not trip the sensor. But if I force it to start with starting fluid it runs. Wouldn't a bad oil pressure sensor continue to be bad????

Sorry to bore those who have now found this continuing saga boring. But I'm just thankful the Good Lord gave me at least minor skills so I can try to R&R these parts myself. Otherwise by now some mechanic would own my car for what the bill would be. I've got no choice but to press ahead. I can't morally sell the car to someone else knowing it has this problem, and I can't drive the darn thing for fear it will leave me standed. Besides, some day someone else is going to have this problem and if I find the solution, perhaps I've helped someone else.

Keep your suggestions coming folks. I'm not out of the dark yet.

topfile

I hope the Oil Pressure Swith works for you. In the mean time try this......

Above the Driver's right leg should be a connector mounted to bottom dash panel.

You'll see two rows of connections.

You'll need to concern yourself with only the top right of this connector
more specifically the last two pins on the top row.

http://www.austinthirdgen.org/mkport...ages/gmobd.gif

Connect A to B.

Using a paperclip or some other wire connect these two pins together.

Get pencil and paper to record the blinks on the Check engine light

To begin the test move the Igntion to Key-On Engine-Off position. The car will run a auto test as you'll hear your fan activate.

Blink... Blink Blink = 12 This code starts and ends the test.

You may or may not get other codes following this code.

Once it's finished turn the ignition off.

You don't need ot start it just key on to start the test and Key off to end it.
Remove the wire.

Report your codes

WileECoyoteSr

Thanks for the suggestion, TopFile. I tried reading the codes earlier in the diagnosis process and unfortunately after I had "rebooted" the ECM a couple of times by powering the car down overnight. When I have had the no start problem after running for some time the ECM doesn't give me anything beyond the handshake initial "1 - 2" code. So it isn't recognizing a sensor fault.

For $15 I went ahead and replaced the Fuel Pump Relay. I did so when the car was still in its "failure to launch" mode. No change. Still would not fire. Wanting to make sure I didn't make a bad situation worse I left the new relay in and forced the car to start using starting fluid. It did and of course like it's done each time it's started ever since without the fluid.

Yesterday even though it was still starting, I replaced the Oil Pressure Sensor. It still starts. But it was interesting how different the Oil Pressure Gauge reads. Previous to the new sensor engine running cold oil pressure popped to 40, now it goes to 60. Warm running used to settle in at 30 now its 45. Slow idle 500 rpm in gear used to drop to 20 or below, its 35 to 40 steady now. Of course I've got Valvoline 10W-40 in her now too and have no idea what the previous owner was running although there was a Valvoline oil filter on it.

Conclusion: The oil pressure sensor needed replacement regardless of whether it fixes the "failure to launch" problem.

Let's count the days until the next time it won't start. I'm running out of things to replace.

topfile

Can you confirm that the Fuel Pump primes(runs 2-3 seconds) in the "failure to launch" mode prior to cranking?

WileECoyoteSr

Topfile: Yes. It has primed during each test. Fuel pressure at the rail prior to cranking is 45 lbs approximately with a boiler gauge type pressure tester. During crank maintains just above 40 lbs. Pump seems to be commanded to run at the appropriate time. I've diagnosed it down to the injectors aren't being commanded to fire when the car is experiencing its "failure to launch" attitude. But if I go out there now, pull an injector wire off #1 and test it, it will fire as the engine starts up now.

Confusing, huh? I'm really hoping it was the oil pressure sensor but I won't know that for sure until I've run it daily for a week if it doesn't strand me. Thank heavens I have AAA.

topfile

injectors aren't being commanded to fire when the car is experiencing its "failure to launch" attitude.

The ECM fires the injector in banks: left and right side of the Engine by ground pulsing, as one side of the injectors are always hot (pink/black wire) through two different 10A fuses.

Did you confirm that both banks of Injectors were not firing or just one side? I undersatnad you did.

If both banks, then:
-the ECM is sensing a problem and refuses to fire the
injectors (ground them) or
-the pink/black wires are not always going hot in the KOEO position.(check both sides of the inj #1 and #2 10A fuses for 12V at the fuse panel and at both injector banks).


If only one bank ;
- then either the dark green or dark blue wire going to
one or the other injector banks is intermittant back to the ECM.(consider examining
the ECM connector for corrosion.)
-The ECM is defective, which you changed.
-One of the injectors is malfuntioning and taking out the bank.

Assuming it's the ECM that is refusing to fire the injectors then we have
a many culprits to consider;

1. Vats detects a problem (you bypassed it so that should be OK)
2. Wires leading into the VATS module are intermittant not detecting the "key" resisitance. Measure the "Key" at the Vats module.
3. Wires leading from the VATS module are intermittant not suppling the 30hz squarewave signal (VATS OK) to the ECM. Measure ~2.5VAC ? at the VATs module
output while still connected.
4. VATS module is defective.
5.Beyond my knowledge...

WileECoyoteSr

Topfile: Thanks for the thoughts.
She did it again. After replacing the Oil Pressure Sensor and having nothing but good thoughts of the car as I made probably a dozen short and long errand trips with it the rest of the week since my last post I had the courage to take my bride for a cruise Friday night (again). Probably without exaggeration a half dozen starts and stops during the evening as we hit the weekly cruise in, and some of the sightseeing spots. Nothing heated like racing. Mostly just 40 mph cruising. All systems normal until we started home and got a "service engine soon" light. But all was running well. It was at 220 degrees but I was in downtown traffic. And you could see the temp drop when the thermostate opened.

Got home. Put it in the garage and restarted it just to make sure. Started fine.

That was last night. This morning my son came over to drive it and it did the same darn thing. Spins over fine but no fire. Tried starting it with Starting fluid but ran out and didn't give it enough of a dose to keep it firing although it tried a couple of times. Ran to the parts store for Starting Fluid and bought a Throttle Position Sensor since that is one of two things not yet replaced.

I returned about an hour later and just for aggravation I decided to twist the key before doing anything further to the car. It started without hesitation!

I went ahead and read the ECM code KOEO and received a 13 which is O2 sensor. All wiring looks good and since the O2 fault is NOT supposed to disable the car, I cleared the code and will see if it will re-occur. I also tested for Closed Loop/Open Loop before clearing the code. It indicated Open Loop by flashing rapidly (2.5 flashes/second).

TopFile: You asked Did I confirm that both banks of Injectors were not firing?
Yes. During the "failure to launch" episodes BOTH banks do not fire (ground) testing with Noid Light.
If both banks, then:
-the ECM is sensing a problem and refuses to fire the injectors (ground them) or
-the pink/black wires are not always going hot in the KOEO position.(check both sides of the inj #1 and #2 10A fuses for 12V at the fuse panel and at both injector banks).
KOEO both fuses #1 and #2 are 12V constant as are both injector banks.

Wiring problem Injectors to ECM?
Visual and wiggle it inspection as far as you can trace within engine bay and from firewall to ECM indicate clean, unmolested and tight connections. Actually, for a car with only 283,000 miles on the clock the under side of the dash is surprisingly clean and as I mentioned, unmolested.

VATS - Although the ignition tumbler switch indicated proper sensing of the key pellets (Key In resistance at steering column harness connection equalled tested resistance of the key pellets) I bypassed ignition switch by installation of an exactly matched (luck, not skill) resistor harness I built and tested with digital VOM. I have not tried testing the voltage at the VATS module. I'll have to figure out where that is before I can test it.

The only two sensors I have not yet replaced as far as I know are the TPS, which I have purchased but not installed because now the darn thing starts again. I'll wait until the next "failure to launch" episode and try the TPS installation then.

The other sensor not yet installed is Coolant Temperature Sensor.

I'm trying to do this one step at a time so that I can discover and share with the 3rd Gen world what the answer is. In the meantime I have an unreliable car in the garage. Thank God I haven't sold the Honda Hybrid yet even though being out of work I'm coming close to the time the extra payments are going to be unbearable. If I don't have the Z-28 reliable by the end of November IT'S GONE! I'll have no choice but to get rid of it.

And what am I going to get for a car that I cannot honestly tell the buyer is reliable?

But hey, that's my life. Ever watch Wile Coyote on the cartoons. That's me. Genius. Pure Genius. Until KABOOM!

topfile

As I understand it the VATS Module does three things once key chip resistor is detected correctly;

1. Activates the Starter Enable Relay
2. Activates the Dash solid SECURITY light for 2 to 3 seconds once Ignition switch moves to the Key-On Engine-Off position.
3. Signal sent to the ECM to tell it to fire the Fuel Injectors

Our 91 5.0L Z28 acted differently.
1. Starter Relay either was not controlled by VATS or the previous owner bypassed it. Or the our 91 is just wired differently at the factory.
2. SECURITY light doesn't time out. It only goes out once it Starts. Also, until I bypassed the VATS key detection the SECURITY light never came on until the 2nd start attemp.
3. Same as #3 above. ECM is sent a 30hz signal from the Vats Moduel to tell the ECM it's OK to pulse the injectors

There is a VATS Module Bypass KIT from Painless Wiring #64023 is available at Autozone or Online....50 to 60 bucks.

You previusly said...
WILL START IF YOU SPRAY STARTING FLUID DOWN THROAT BUT WON’T REMAIN RUNNING.

I have not tried testing the voltage at the VATS module. I'll have to figure out where that is before I can test it.

I think the VATS Module is on the Passenger Side undeer the dash. Not sure though.

How does your Security light behave? Exactly.

WileECoyoteSr

TopFile
WILL START ON STARTING FLUID BUT WILL NOT REMAIN RUNNING WAS ONLY THIS ONE TIME BECAUSE I RAN OUT OF STARTING FLUID AND DIDN'T GET ENOUGH DOWN THE INTAKE. Every other time I've forced it to start by using starting fluid with the throttle partially open to about 2,000 rpm on start up it has worked and the engine performed marvelously for days afterward. Then I'll park it in the garage and the next day or so that I try to use it the car won't start.

VATS on my car, whether it is starting normally, as it has now all afternoon after it decided to heal itself, or during the episodes of "failure to launch" is the same and per specs as I understand them which is : Activates the Dash solid SECURITY light for 2 to 3 seconds once Ignition switch moves to the Key-On Engine-Off position.

My 91 Z with the 5.7L L98 acts the same as yours. Even if VATS is unplugged at the steering column the starter still spun. It just would not start. I did not test the NOID lights with the VATS unplugged at the steering column because the NOID light wouldn't fire when I had it rented for the last "failure to launch" occasion.

I thought the resister harness placed in the connecter under the steering column was supposed to be a cheap alternative to the VATS bypass aftermarket system you mentioned. Was Chevy 8588 incorrect on that and a module bypass is needed?

I do not see a VATS module on the Chiltons wiring diagram, or systems drawing for the 91-92 L98 5.7L. Chiltons indicates the VATS simply transmits the resistance of the key pellet at the ignition tumbler to the ECM and the ECM then commands whether or not to fire the injectors and turn the starter. Can someone tell me whether the 91 Z L98 car has a separate VATS module, and its location? My Chiltons tells me that the little black box mounted under the right dash beside the ECM is the cruise control module, which may be burnt out on my car since the cruise control decided to quit when I power washed the engine bay early in this routine. Could the VATS and Cruise Control be in the same module?

But the car was having this "Failure to Launch" for the previous owner, evidently. (Did it to him twice and healed itself both times) So I don't really believe my power washing the engine bay had anything to do with the engine intermittent problem.

The car started fine this afternoon and evening. Again more than a half dozen starts without hesitation to fire. Want to make a bet that tomorrow morning if I decide to take my Z to church, it will not start?

WileECoyoteSr

By the way, I apologize to the moderator and anyone who has had the patience to follow this thread for the length of it. First, I'm kind of a detail guy. Ask me what time it is and I'll tell you how to build a watch. But more important is the fact that this is a problem that I've seen out there. Others have found an answer for their cars, evidently, but that same answer - whether it is bypassing the VATS or replacing the Oil Pressure Sensor - has not resolved this problem. Our cars have another gremlin in them and I truly hope that finding the answer to my car's problem will benefit all 3rd Generation Camaro owners. So bear with me. T.W.

topfile

I thought the resister harness placed in the connecter under the steering column was supposed to be a cheap alternative to the VATS bypass aftermarket system you mentioned.

To truly bypass the VATS one needs to generate a 30 hz 5V squarewave signal to the ECM. That's what the aforementioned module from Painless Wiring does as I understand. The resistor trick is only part of the story.

The inconsistant way your Z28 acts is certain puzzling.

It makes me think that you're not having one single problem but two.

Something to keep in mind is if VATS detects a problem or the ECM looses the
30hz signal. It doesn't matter what you do it won't start for 4 minutes.
One must wait before a new valid start attemp is detectable and allowed by VATS
and the ECM.

Senario: Intemittent VATS operation prevents you from starting on your first attemp. You try several mores times within a 4 minute window. Each subsequent attemp
causes the 4 minite timeout to reset. It takes you more than 4 minutes to get the
air intake hose off the trottle body to squirt starter fluid. You try again. It starts
and you assume it's because of the starter fluid. Reality was simply an intermittant
VATS. Is this possible?

Next time this happens try once and wait 4 minutes between attemps.

You'll likely not see a VATS diagram because of the Theft concern.
here's a 91 (page 27 and 28) http://www.fastgm.com/wiring/91CamaroWiring6of6.pdf

and a 92 theft deterrant
http://www.austinthirdgen.org/mkport...m_pass-key.jpg

WileECoyoteSr

Hmmmm. Very, very interesting! You may have struck upon something. An intermittent VATS module. Okay. It's been a long day for me and I'm not quite thinking clearly. But let me noodle that. After all, another $50 or so is less than the $500 deductible if I torch the stupid thing! (Just kidding!).

Okay. It's sitting there and it knows it won't start for some reason. Let's presume the VATS goes bad sitting there after I've parked it and let it rest over night. I climb in and attempt a start time and again with no results. As you mentioned, its calling for a 4 minute time out before it will hand shake and fire. And each time I attempt the start it is resetting the 4 minute clock. So I give up and exit the car, pop the hood, dig the starting fluid out of the trunk locker, take the snorkel hose loose, hose it down, enter the car and attempt a start.

Now at this point I have to sit back and look at past history. Each time I've tried to force it to start at this point in the scenario with starting fluid it has, indeed started. Except this morning. This morning I ran out of starting fluid and aborted my start attempts. I removed the key from the ignition and came back one hour later and it started unassisted.

No change in temperature in the garage. No movement of the car. Simply ceasing the attempted starts and then returning to start. If we theorize the VATS Module is defective it could be that at some times when the signal hits to module it reads it right. And at other times for some reason it doesn't read it. It would have to be something electronic instead of mechanical or physical.

I can see this theory working. I'll look into getting the VATS bypass you mentioned.
It may take me a couple of days. I'll report my results when I've had a chance to install it and test start it a few days.
Thanks. T.W.

topfile

I'm trying to think of a senario that fits. This one seems plausable. The
VATS module is intermittent is a possibility. Wait the 4 minutes next time
and see what happens before you consider replacing it.

IS it the wires to the module, power to it, 30 hz signal, or the Module itself?

A total bypass of the system could do it. Try the 4 minute thing first.

Something else to view.....

http://articles.d-tips.com/GM_Passke...s/image001.jpg

WileECoyoteSr

Well no answer yet. Went away for half a week and when I left the Camaro was starting every time. Came back Friday evening and she wouldn't fire on the first try. Tried it just once and turned off the key and walked away for ten minutes muttering. Returned to the car and tried to start it again and nothing. Will not fire. Did this three times with more than four minutes in between attempts and no fire.

Filled the intake with starting fluid and it started.

I really don't think this is indicating an intermittent VATS since it will start if I use starting fluid. And it will start with Starting Fluid each and every time. And once it starts with Starting Fluid it continues to start. Maybe I should count how many times it successfully starts before it fails again.

Since I already bought the Throttle Position Sensor (TPS) I'm going to install that next time if fails to start and see if that magically fixes the problem rather than forcing it to start with starting fluid. I'm also going to go rent the NOID light again before I do anything else the next failure. Now all I have to do is wait for the next time it fails to start. Now isn't that special?!?! Luckily so far the "failure to fire" has always been in my garage. And no, it isn't a pressure cooker, an extreme floor angle or a time warp vacuum in there.

If I am not mistaken, the only sensor I will not have replaced once the TPS is replaced is the Coolant Temperature Sensor (CTS). Check me on that tech fans. This is getting down to the sad end of all the suggestions out there.

y84pauloflondon

Have you tried disconnecting the MAF sensor, placing the car in limp mode and see if its starts? I too have same problem, since last sunday I can not start my car. Took it to a local stealership to get it fixed. They told me that it needed a New MAF sensor, I bought a reman MAF for it....... nothing, no change...... so lets see what they come up with now!!!!!(wire wiggle test...lol).

Car WILL run disconnected from MAF sensor.

y84pauloflondon

Quote: WileECoyoteSr-
"After all, another $50 or so is less than the $500 deductible if I torch the stupid thing! (Just kidding!)."

LMAO, I know how you feel, its frustrating as hell...cause I need my car for MY wedding thats in 4 week... thats why its at the stealership and not at home doing the work myself.

WileECoyoteSr

I'll try the MAF sensor disable next time it acts up. As of yesterday it still runs. My first attempt at fixing it the next time it has "failure to launch" will be to replace the TPS. If that doesn't get it firing I'll do the MAF sensor disable.

There has got to be a logical answer to why the injectors won't fire, but if I force it to run on Starting Fluid I can start if over and over again by key after that.

y84pauloflondon - did you try starting yours with starting fluid before you relinquished it to the dealer?

WileECoyoteSr

oops. repeated myself.

Chevy8588

iTrader: (1)

sounds like the hall effect sensor inside your dizzy is rusted up, injectors wont fire unless it detects the engine is turning, by running the starting fluid through you probably spun it fast enough to chew it all off

WileECoyoteSr

That hall effect sensor suggestion is interesting but one of the first things I did was replace the coil and the ignition module. I did not replace the magnetic apparatus on the distributor the name of which I cannot recall and as much rain as is coming down I'm not trudging to the garage to get the manual. Is that piece plugged into the ignition module capable of telling the injectors not to fire?????

Chevy8588

iTrader: (1)

that magnetic apparatus is you hall effect sensor (not sure if that's what is was called back then but that's what they called them on later cars) it tells your ECM that the engine is spinning and to fire the injectors, it BASICALLY works as a camshaft positioning sensor, without this you will have spark all day long and no fuel

WileECoyoteSr

Yikes. I read the Chiltons on that when I replaced the Ignition Module but it didn't explain it to that detail. Looks like its time to dig into that part of the beast. If I remember the manual correctly, the distributor has to come out to get at that part.

Do you think the intermittent problem might really be there?
I mean it could be. It seems when she decides not to fire the injectors it is after the car has been running beautifully for a number of days and then I park it for a day or two.
It's not a either it works or it doesn't piece?

Your input is deeply appreciated.

Chevy8588

iTrader: (1)

i had problems with mine and every once in a while i would get a no start condition, i'd crank and crank and crank, checked and it had spark but no fuel, then finally i pulled the cap and wiggled the distro shaft (noticed that sensor is rusty as ****) put the cap back on and it fired right up, ran smooth got about 19 MPG no performance drops at all, and it would USUALLY happen after the car sat for a week or so when i was keeping it at my old work to work on it over winter (Ex-GM tech here) replaced the dizzy, (new hall effect and all) hasn't happened since.

y84pauloflondon

No I did not use starting fluid. When this S**T first started it took me 10 mins to get it started(car). Ran fine, then I shut it off, tried again...Nothing. It would fire up for a second or two and then it would shut down. It really did sound like it wanted too start. So at first I thought I had a weak fuel pump on its way out. Today the dealer told me that the reman MAF I bought on Friday is no good, I need to get another......WTF!!!! But they did check ALL my relays and connections under the hood, "everything looks good"- Dealer. They did NOT check the ECM though....NOT YET....

Chevy8588

iTrader: (1)

did they even hook a tech 1 up to it? thats the only way they'd be able to tell if the maf is good or not, and it might just mean a break in the MAF circuit, this dealer sounds like they are full of themselves

y84pauloflondon

So on friday night I had my car at home, put the new reman in, no change at all. My buddy came over with his laptop and OBD 1 connecter with software. Laptop showed that I got CODE 33 and 34 on the car.........Thats Just F***** Great.....

y84pauloflondon

Well they told me that the reman is putting out 4 ohms when it should be 20 ohms......what ever that means?

y84pauloflondon

Believe Me, I would love to be there and watch them work on HER... But I need to work to pay off the wedding.

This is the first time She's seen a mechanic in 6 YEARS, everything untill now was by ME.

WileECoyoteSr

Well I checked the Chiltons and that wasn't where I saw the instructions on replacing the magnetic pickup. If I remember the instructions it wasn't the easiest thing to do. I might be better of with a new distributor like you put in. Did you go with a GM replacement part, an OEM from a chain, or a high performance replacement?

HEY y84pauloflondon TAKE NOTE OF THIS. Could it be your pickup coil in the distributor like Chevy8588 experienced? Sounds like what mine has been doing.

Chevy8588

iTrader: (1)

i got an OEM replacement for now, gunna get an MSD one with a Blaster coil soon

camarohelp

In regards to your private message regarding VATS

I do not suspect that your problem is with the Anti Theft System. Here is why:

1. You did not mention your orange security light. Normally the light comes on for a couple of seconds after the key is turned and then goes off. When either the wrong key is inserted or the VATS is malfunctioning, the security light will STAY ON.

2. When the VATS locks out the car, the engine will not turn over. There is a STARTER ENABLE RELAY which is only enabled when when the VATS reads the correct resistance from the key. Note, however, that this relay can be bypassed, so that the engine will crank even with the security light on.

3. Probably what is most important is the fact that your car will start with fluid, implying that the injectors are firing once the engine starts. In '92 Camaros, if the VATS fails to detect the proper resistance (or malfunctions) and throws the security light, the fuel injectors are disabled for some time, I believe between two and seven minutes (I am not sure, I haven't studied this for a number of years). In other words, if you had a VATS problem, the engine would NOT run, even if you succesfully turned it over and sucessfully ran the engine off of starter fluid for a few seconds.


The bypass that I mentioned having to do was more detailed than the simple resistor-based bypass, as the malfunction was not with the resistor but somewhere in the VATS processing hardware. I ordered a programmed PROM with VATS disabled (something I can now do myself) and bypassed the STARTER ENABLE RELAY.

It may help to check the relay and see if it has been tampered with. As I remember, you'll find it under the steering column, near the body toward the driver wheel. Its a plastic cube maybe two inches wide with four-five wires running into one side. Mind you I did this years ago, so I may be a little rusty on its appearance and location. If you are not sure about how to tell whether or not it was tampered with, send me another private message.

But if the 1991 VATS is identical to the 1992 VATS (and I suspect it is), I strongly doubt your problem is with the Anti Theft System. Good luck.

y84pauloflondon

I'm glad that the new dizzy and cap are working out for you, Chevy8588. (Well Done).

WileECoyote- My car runs good (Not Great) on Limp Mode (MAF sensor dissconnected), if I reconnect it (MAF Sensor) the car WONT start....Isn't that B***S***... So I think the cap, rotor,diss and dizzy is Not my problem!

Thankx anyway....BEEP BEEP

Chevy8588

iTrader: (1)

sounds to me like you have a partial break or ground in your MAF wiring or a corroded contact in your connector, i'd trace all the wiring back through the harness, if that doesn't work id replace the connector, also check the MAF relay

y84pauloflondon

Well the stealership checked all relays and all conecters, they said that everything looks good except the new reman MAF I bought on friday. According to them the reman I bought was crap, we'll see tomorrow when I bring another.

Please read post #37, 40, 41

y84pauloflondon

I Really hope that my problem IS my MAF. If not.....I've got a BADDDDDD feeling it might be the ECM though....

Chevy8588

iTrader: (1)

lol take it to dave from dave's farm! he'll fix it! lmao, but in all seriousness, your new MAF COULD be doa, I HAVE seen it happen. also i dont know about other dealers but the one i worked for was really honest, and in all reality, changing a maf only pars a journeyman 10 bucks so I dont think they are blowing smoke out their asses.

y84pauloflondon

I'm not trying too say that all dealerships are cheats, but sometimes I think they do. I've had very bad luck before at a dealership cutting corners, which costed me my org. engine block!!!(numbers matching).

This dealer charged me $95.00 extra cause I have a magnaflow muf welded on, they say that the factory muf was bolt/clamped on. When my car wouldn't start I thought it was do to a weak fuel pump. To change it(pump), the exhaust had to be moved out of the way to drop the gas tank.

Honestly, it probably took them 10 mins longer then having stock exhaust, which I think was welded on aswell.