About a week ago I bought a '91 RS w/ the 305 TBI, it was in non-running condition, but it was sold to me by a good friend of mine, he bought it a few months ago to fix it up, but never got around to it, and didn't really know how

The car is in ok condition, some rust on the underside and needs to be repainted soon, but the main problem was the wiring harness, it was completely melted in the rear driver's side corner of the hood, apparently somebody poured gas on the hood and lit it on fire or something.

I'm an electrical engineering student at UT Austin, I was able to easily fix the damaged wiring with parts from the junkyard (harness, fuel pump relay, etc), and all the electrical systems in the car work now, the engine cranks over, radio/gauges/lights all work

I even got the car to start a couple times, but it would only run for 8-10 seconds at a time, then it would stall. Once the engine started the SES light would go off though.

With a friend looking into the throttle body while I was trying to start it, we determined it was a fuel pressure problem, I replaced the fuel filter, it was pretty clogged, but it's still not starting now, not even for a few seconds like it used to.

Is it possible that I blew the fuel pump when trying to crank it with the clogged filter? I tried another fuel pump relay, but that didn't do anything. I still have yet to try listening for the hum of the pump.

So anyways, since I'm kind of new to these cars (though I've worked on a bunch of other cars before), I have a few general questions:

When the engine is off, but the key is in the "on" position, should the fuel pump be on? Or does it only turn on when the engine is actually running or trying to start?

On the driver's side of the firewall, there are a few components that plug into the main harness. I know one of them is the fuel pump relay. What are the other 2 things? There's another relay, but I'm not sure what for. Then there's a flat square thing with a 5 pin connector, I have no clue what that is.

Finally, are there any articles/tutorials on how to drop the fuel tank? That seems like the most logical step in trying to diagnose my fuel system problem.

Thanks,

-Tim

PS. First post! Glad I found this site

 

M4xx Welcome to TGO

About your '91 - nice find.
The fuel pump circuit will come on for about 2 seconds once your turn ignition key from ACC to RUN position. Apparently old general thought it was enough to prime fuel system. Fuel pump circuit is controlled by ECM - once it sees DRP signal from dizzy it will turn on fuel pump and will keep it on as long as DRP's are present. It's a safety issue.
To test your fuel pump you can use jumper wire between FP relay socket and battery - this will force FP to turn on. WARNING - watch for gas leaks, etc. I strongly suggest that you get fuel pressure tester from AZ.
TBI systems do not have fuel pressure test port. To test fuel pressure requires disconnecting the drivers side fuel inlet line, inserting tester adaptor / gauge and reconnecting the whole thing to the injector pod. You can find instruction for fuel pressure testing with FP test kit or online. Stock GM TBI systems run 11 to 13 PSI - it must be steady while FP is operating.
The five pin connector thing is probably ESC - electronic spark control module - it is used in conjunction with KS to retard timing when engine pings.

Post pictures - and will try to get your RS road worthy again - you just got to be patient - just like troubleshooting circuits on the bench.

//RF

 

Thanks for the suggestion, I actually tried jumpering the FP realy like you suggested, it worked! I went under the car, I could hear it humming, and there weren't any leaks

Still havent checked fuel pressure, Im waiting for my battery charger to charge the battery, I ran it dead in my experimentation trying to get it started

Now that I know the FP works (just hoping the pressure is good), I think it wasn't starting simply because fuel hadn't reached the engine yet (since I replaced the filter), I wasn't able to crank it very long cause the battery went dead.

I'll keep yall updated.

Here's some pics BTW:


Kind of a shitty paint job, the car was originally red, it's pretty obvious under the hood

The melted harness:



Also I forgot to ask earlier, but there's a cable going from the TB to a little module just to the left of the washer fluid tank, whats this for? This cable was also damaged significantly, but I haven't fixed it yet cuz I'm not exactly sure what it is

 

Could be bad gas. How long has it been sitting in there? If it's more than a year, just siphon it all out and run a tank of premium through it. Might fix your problem.

 

Yeah I'm not sure how much gas was originally in the tank, the fuel gauge doesn't work, it's stuck at the maximum limit of the gauge (way past "F")

I put a couple gallons of fresh premium and some FI cleaner in there though

Whats the most common cause of of a dead fuel gauge? The sending unit in the tank? I've read some about cutting an access hole in the trunk to remove the FP, I might try that

 

If you cut the panel, be prepared to cut all of the lines that lead into the pump/sender assembly. It's hardline up there. The correct way is to drop the rear end and the tank, which if the car is already not running, I see no reason to avoid dropping the tank.

Plus, you can get rid of the rust up there and POR-15 the stuff, or whichever flavor of undercoating you prefer.

 

Yeah I was considering that, but it's gonna be a major PITA to drop the rear end with the tools I have, though it is a better solution

 

Buy a tool set. Tools are ALWAYS a good investment. Only buy stuff with a lifetime guarantee too. I buy the powerbuilt tools from Checker and Pep Boys. I've dropped them, vice gripped them, covered them in oil, tranny fluid, gasoline, the list just goes on. After a good wipe down they all look brand new.

 

Well it's not so much that, I got a crapload of sockets/wrenches/etc., it's more that a job like that would be way better suited to an actual garage, I'm just working under the carport in my apartment complex (where they don't really like people working on their cars too much), plus here in Texas it's pretty damn hot, I was all hot and sweaty and miserable just replacing the fuel filter, and I got some sort of ear infection thing now from getting gas in my ear

yesterday I went inside for like 20 minutes to make somethin to eat, came back out, and somebody was tryin to steal my jackstands, guess that's the problem with living downtown

 

ok, another update:

The battery has charged, so I went and tinkered some more:

It still won't start. I first made sure that the FP was actually turning on when cranking the engine, when first turning the key to "on" I can hear it turn on for about 2 seconds, and I confirmed that it's turning on when cranking with my voltmeter.

But still, there isn't a drop of gas coming out of the injectors

Next, i checked for fuel flow. I loosened the fitting where the fuel line goes into the TB, to see if gasoline would drip out. Turned the key to on, and got a nice little trickle for 2 seconds.

So, it seems that the fuel injectors aren't working ECU problem???

 

Grrr. I can't get it to show any trouble codes. It just keeps flashing "12" over and over and over

 

M4xx

Code 12 when you short pins A & B together and nothing else indicates that it is all good from ECM perspective.
Hmm - we still need to know if you got fuel pressure when cranking. Now, that the system is primed you need to check couple of things.
Having weak battery sucks.
It's very common for these cars to have FP in tank hardware to fail - we see at least one or two a week here. What do I mean by that - it can be fuel pump itself or sometimes the rubber hose between FP outlet and sending unit crack due to age. The pump maybe working, but fuel never reaches TB - that is the reason to test fuel pressure before heading any further. Soooo, with that in mind rent FP tester from autozone or your other favourite auto parts store.
From the picture, it looks like the driver side firewall got scorched - that bracket above electrical connector is used to mount a pair of relays. Since I am not familiar with 91 electrical layout I can not offer good advise. Pegged gas level indicator may indicate that this circuit is open - without manual I do not know were gauge wiring passes through to tank.

How much of that wiring harness have replaced - repaired so far?? There are couple of circuits in there that supply power HEI and starter enable signal.

//RF

 

from the second last pic it appears you have no relays where they should be on the firewall,

 

Those pics were taken before I repaired any of the damage, thats how I bought the car. I never would have even tried to connect a battery with the wiring in that condition, not to mention tried to start the car (unless i wanted to fry it even more)

I hacked off the melted part of the harness, took it up to my workbench, and replaced every piece of damaged wire with matching colored wires that I got from the harness from an '89 camaro I found at the junkyard, I also replaced the two relays and the other flat square module that is in that area of the car. (note I figured out what the other relay is, it turns on the cooling fan lol)

After I soldered and heatshrinked in the new pieces of wire, I soldered it back into the car. I took a lot of pictures and labeled similar colored wires with zip ties, etc. to make sure I reassembled the harness correctly. I'm like 99% sure I did the wiring right since I did get the engine to start at one point, and all the electrical systems in the car seem to work except the fuel gauge and windshield wipers, and I can only get air to blow out of the defogger vents.



I'm gonna get back to work on it today, check fuel pressure, and check to see if there's pulses going to the injectors.

I guess if there aren't any trouble codes then the ECM is good, right? I was concerned abut it being damaged during the fire (since a bunch of wires all shorted out, the car had a lot of blown fuses)

 

Yeah I'm about to go to the autoparts store and find a fuel pressure gauge.

So if the pump is working, but there's still low pressure, then it's repairable, correct? (ex. I don't need a whole new pump, but just fix that hose that might be damaged and/or replace the strainer?)

Can the FP be disassembled and cleaned out? Or is it a non-serviceable unit

Will the ECM not even try to open the injectors if fuel pressure is not sufficient? Because before I changed the fuel filter it would at least drip SOME fuel out of the injectors and the engine would try to start, now there's absolutely nothing.

I may have clogged the strainer or the injectors in my earlier attempts at getting it started.

 

Can the FP be disassembled and cleaned out? Or is it a non-serviceable unit?

FP is a small serviceable unit, about $50 to $70; strainer is also replaceable unit.

Will the ECM not even try to open the injectors if fuel pressure is not sufficient?
ECM will fire injectors regardless of fuel pressure - all it needs is DRP pulse from dizzy to enable fuel pump relay and start firing injectors. This needs to be verified. Make sure that you are getting 12 volts at injector 12 volt supply wires (red). All ECM related wire harness is passed through on the passenger side of engine compartment.

Because before I changed the fuel filter it would at least drip SOME fuel out of the injectors and the engine would try to start, now there's absolutely nothing.



I may have clogged the strainer or the injectors in my earlier attempts at getting it started.[/quote]

 

OK, I got a fuel pressure gauge, it is still a fuel pressure problem.

Also for the hell of it I removed the injectors from the car, and they've been soaking in FI cleaner, they look a lot better now, and I tested them with my 12V bench power supply, both of them make a nice little "click" when applying 12V, so the injectors aren't stuck.

When I first tried starting the car, the fuel filter was almost completely clogged (after I removed it, I could barely even blow any air through it with my mouth), so I believe this backup in the line created too much pressure in the line from the FP to the filter, damaging either the FP or the rubber hose from the FP to the sending unit

So, either way, the problem is in the tank. My fuel gauge is dead anyways, so may as well take care of all this stuff at the same time.

Time to go figure out how to drop the tank >_<

Thanks for all the help guys

 

Gurantee it is the fuel pump or even the little rubber hose inside the tank that connects the fuel pump to the fuel line.

I've had the same problem twice before putting a high pressure fuel line designed for racing engines in there. Haven't had a problem since and both times my fuel pump was good.

 

M4xx

Dropping a tank is not that tough provided that you have a helper and an empty tank. I did it by myself and it was an adventure trying to balance the damned thing on the jack, without ripping all the hoses, etc apart. Having a helper makes it manageable.

About a fuel pump - the going consensus on this board to get a delco replacement. China made pumps are pure junk - they do not last long and crap-out at the least opportune moment. Furthermore, when you get your pump make sure to replace in tank fuel hose with submersible fuel line hose that meets or exceed the SAE 30R10 rating, which is the standard for a submersible fuel line hose application. Not all stores carry this stuff - look for identification label.
Fuel level indicator is nothing more than 90 Ohm pot - near 0 ohm when empty and 90 Ohms when full. I also found this link that may help you with gauges.

https://www.thirdgen.org/forums/elec...lectric+speedo

//RF

 

Also, can't the TBI pumps be swapped with TPI pumps and have the pressure upped with no ill effects? I remeber reading that, but would like someone to confirm it. If so, you could get a Walbro pump that does something like 255L/h. Only like $200 or so, I believe.

http://www.racetronix.com/RX-FL98-FPKG-2.html

 

Scary

Yea, you can retrofit TPI pump in place of TBI pump. However, the fuel pressure regulator will be bleeding a lot of fuel back into the tank. Consequently, TB fuel pressure regulator spring, which sets working fuel pressure that TB injectors will see, will be working OT.
Walbaro makes some of the best pumps in the business, but the rest of the fuel delivery system may not be up to par - one must go through the whole system and replace all rubber hoses, check all fittings, etc.
Circulating fuel so much fuel will inevitably raise its temperature, which is not good either. Warm gasoline does not cool pump as well as cooler gas plus it creates a lot vapor pressure which can be a problem.
M4xx is a college student - $200 walbaro pump is probably not in his budget. Having a cool car is.

//RF

 

All right I got the tank out! Damn it was a bitch and a half... I was able to lower the rearend pretty far but couldn't get the cross brace from the passenger side of the frame to the drivers side of the rearend loose, the bolts were rusted on there pretty good. Oh well, I was still able to get the tank out, just took a long time, and cut my hands up

Next step: how does that ring thing on the top of the tank work?

 

Ok, I figured it out.

Yup, the rubber hose inside the tank was completely disintegrated.

Off to find some 30R10 hose...

Also, how the hell are you supposed to get the FP assembly out of the tank? I can get it about 90% of the way out then the strainer and the float are in the way.

 

M4xx

You have to tilt and squeeze float arm a little bit to clear gas tank opening. Check the link below:

http://www.edgesz28.com/edgesZ28/sub....____Fuel_Pump:

Strainer can be somewhat folded - it must be replaced.
Warning - it is false economy to retain original strainer. Over the years strainers tend to accumulate all the crud and gasoline additives will slowly eat it away. Also, I hate to say this, but original FP may be close to going out. Dropping a gas tank twice is not my idea of having fun on a hot day - I know it's a bit of money, but get it replaced while you have a chance! Sorry dude, I have been there and done that.

Get your DVM and verify float potentiometer value 0 to 90 Ohms while moving it up and down at the interface connector.

//RF

 

All right, I replaced the hose and strainer, and cleaned out the FP with some denatured alcohol, and ran some through it while running the FP off my bench 12V supply. It sounded pretty healthy, a nice electric motor type sound, no buzzing or grinding, flow is nice and strong.

I also fixed the fuel gauge, it had corroded and gone high resistance, I disassembled it and cleaned it really well, it works now. The float arm also had a poor ground connection to the fuel line (where the ground wire connects), so I soldered a small piece of wire from the float arm to the line, and left a little loop so the arm can still move normally.

At first I was still having trouble getting it started, i determined it was flooded, I unplugged the injectors and cranked it till it started and ran out of gas. Plugged the injectors back in, and she fired right up!!!

It made a TON of dark smoke, but I kind of expected it, this thing hasn't been run in at least 3 years. It's got a really rough idle, and it sounds like it's super rich, but other than that it runs ok, decent throttle response. The SES light came on almost immediately though, codes 15 and 22.

15 is low coolant temp, I guess this is a bad thermostat? (stuck open)

22 is something up with the TPS, I'll have to go look at that. Could have something to do with the melted cable going from the TB to some black thing by the washer fluid tank, I still have no idea what that thing is.

Also my tach is WAY off, just cranking it reads 700-1000 rpm, a low, lumpy idle reads like 2500rpm, and I can run it off the gauge by just barely tapping the gas. lol

 

M4xx

Are we having fun now??? I guess you are.
Lets take a look at codes 15 and 22 together - hmm. Code 15 is easy to check. CTS is located right by thermostat housing or on some installations in thermostat housing. It is a two wire device - thermistor. Its supposed to be very high resistance at -40 C ~ 10k and about 120 ohms at 150C. To check disconnect wire harness connector (one the wires should be yellow, the other can be black) measure CTS resistance with DVM. At room temperature (25C) it should be around 2700 Ohms. If this reading is significantly off - replace the silly thing. Also, check ground line (black color wire) Pin A at harness connector - measure resistance between it and engine ground. Note that TPS shares the same ground line (code 22)! If you are reading high resistance to ground check ground lugs at thermostat housing and at the back of the passenger head. Clean all ground connections! Also check for broken, ripped wires inside wire harness.

Photo is of my conversion setup identifying TPS and IAC locations on TB. Second Photo shows CTS location on my setup - yours maybe different.
//RF

 

I am in a similar situation; living in apartments with no garage. I have been working on redoing my interior and I can not run up to my apartment with the hatch or doors open for fear of someone trying to steal something! Sorry to jump off topic. Good luck.

 

Hmm I'm still not sure what's up with the CTS and TPS, I measured the resistance of the CTS after the engine had been running for 5 minutes or so, it was 1073 ohms, seems about normal.

The ground connection is good as well, I measured less then 1 ohm from the black wire on CTS and TPS to the battery negative, and from the batt. neg. to the engine and chassis.

It must be a bad connection on the sense line somewhere. Do these two sensors connect to the ECM through the big plug on the drivers side of the firewall? Cuz I've fixed a couple of other intermittent electrical problems on the car by wiggling this connector, I think I need to take it off and clean it some more with contact cleaner.

Other than that, my current list of things to do on the car includes:

-Change engine and transmission oil and filters (tranny gasket needs replacing anyways, it leaks)
-Flush coolant and replace thermostat and thermostat cover (it has a small hole in it)
-Replace vacuum hose going to the canister, it's melted all the way through, and probably replace canister element as well
-Replace the cable for the idle speed controller thing
-Replace the air cleaner (I'm most likely gonna do the ultimate TBI mod)
-Spark plugs and plug wires (the engine seems to run good, but I have the parts already so may as well replace em)
-O2 sensor
-Overhaul the brakes, and I've got new wheel bearings to put in there too
-New tires
-Readjust the high beam switch (it only works with the steering column down all the way)
-Recharge the AC if I have the money, the AC works, just not super cold

Hopefully after changing the oil and letting it run some more it will stop smoking so much, there's no way I'm gonna get it to pass emissions like that

I still haven't been able to drive the car at all, I need to fix the tires, brakes, and transmission before I can do that (I think the tranny is either out of fluid or just really low, putting it into reverse/drive/low does absolutely nothing), I don't trust the brakes in their current condition either, a LOT of rust came out of the rear drums when I was screwng around with the fuel tank

Oh well, progress is still progress. I found a local third gen club too so I'm gonna go check that out this weekend

 

M4xx,
Congrats on the find and great job getting it running. Keep us posted on all of your progress!

 

Sure will. I'm kinda new to this but I've got a pretty good general knowledge of how this stuff works, and I'm learning VERY quickly.

I can't wait till I get the car running good and drivable, that's when the fun stuff happens (mods/upgrades). Currently I'm just trying to get it to work.

 

'M4xx

The best way to troubleshoot codes is too have Tech 1 display or a Lappy with ALDL cable and WinALDL software.

If CTS sensor is reading 1073 Ohms after 5 minutes of running that's about 49C (120F) - its probably about right depending on the thermostat. Disconnect CTS connector at the sensor - measure B terminal (yellow wire) with respect to ground - it should be around 5 volts +/-10%. If you are getting nothing - locate ECM (mounted behind passenger foot panel). Disconnect negative terminal at battery, then disconnect the two harness connectors at ECM (watch for connector latches). Verify Pin C10 to Pin B of CTS connector for continuity. At the same time verify the following connections:
A11 to Pin A of CTS Sensor GND (Blk wire)
A11 to Pin B of TPS sensor GND (Blk wire)
C14 to Pin A of TPS sensor +5 reference (Gray wire)
C13 to Pin B of TPS sensor TPS signal (Drk Blue)
Also check for ground shorts (except for gnd reference wires)

TPS is a simple variable resistor!

Code 22 will be set if:
Engine is running
TPS signal voltage is less than 0.20 volts.

If you disconnect TPS connector and jumper TPS connector pins A and C together should cause ECM to sets Code 21 (high TPS voltage). This indicates that both ECM and wiring harness are OK.

Code 15 will be set if:
Engine is running longer than 30 seconds
Coolant temperature is less than -33C (60 kOhms)

You can verify CTS circuit by jumpering pin A and B together - This will set Code 14 high temperature and will indicate that ECM and harness ok.

BTW, Code 15 will make engine run very rich!
//RF

 

Thanks

I'll go try that, basically the same process of elimination I've been using this whole time to fix the car, just needed that info

Y'all are helping a LOT, I never would have gotten this far without finding this site

 

Hmmm.

Jumpering the TPS sense wire to 5V does cause code 21, so all is good there. I will try adjusting the TPS and/or replacing it if it's broken.

I'm getting 12V at the CTS yellow wire though, not 5V.

When jumpering to ground, it draws 183mA of current, and the electric cooling fan turns on. However, the ECM still displays code 15, not 14. When starting the engine, the coolant temp. gauge jumps to full hot for 1-2 seconds, then goes back to full cold. The SES light comes on after about 30 seconds, with code 15 still and 21 (since I jumpered the TPS sense to 5v)

Sounds like a circuit in the ECM is possibly damaged?

I'm gonna try and make an ALDL cable, but my laptop is retarded though and doesn't have an RS232 port, only USB and parallel

Will winALDL work with a USB-RS232 adapter? Or is there a way to do it through parallel?

 

M4xx

TPS - Verify TPS idle voltage (dark blue wire) it should be between 0.2 to 0.6 Vdc. You can also verify resistance variation between Pin A and Pin B of the TPS. The range should be between 1 k to 6kOohm (or in reverse I always screw up on this one). Idea here is that it should be nice, continuous resistance variation - sudden drop out means TPS is NFG. Time for a replacement. You can also verify of idle voltage as well - it should be continuous variation from 0.6 to 4.4 at WOT

CTS The fact that cooling fan comes one is good - ECM thinks that it sees very high coolant temperature and turns on cooling fan. I could be wrong on this one. Some cooling fan control systems used independent sensors to control radiator fans! I am very concerned that you are seeing +12Volts on yellow wire (TPS). Which ECM do you have in your Camaro? - post service number and broadcast code from the label.
I am not familiar dash gauge behavior, but I know that dash temperature gauge uses its own sensor. So its behaviour should be independent of ECM operation. We'll address this later

WinALDL will work with USB to RS-232 converter board. Do a search here for thread. You can also get ALDL to USB cable. But I know you will make your own cable using couple of transistors - just make sure you put everything inside a box!

 

Yeah I'm gonna make the cable and get a usb to serial adapter from the local electronics store

I'm really confused as to why the CTS sense is 12V instead of 5V (and still shows code 15 when grounding it), I suspect an ECM problem, winALDL should give me a lot more info as to what's going on here.

Plus I'm gonna need it later anyways once I start modifying the car, I've already read up some on PROM burning and such.

If it is an ECM problem, whats a good (but relatively inexpensive) aftermarket ECM to use?

 

'M4xx

I did a bit of head scratching. CTS circuit should not have +12V bias on a yellow wire - it should be +5 Volts. CTS has a close cousin - MAT (Manifold Air Temperature) sensor. The two sensors are nearly identical except the later is used to measure manifold mixture temperature. Look for Tan color wire (ECM Pin C-12) along with black wire tied to connector similar to CTS. Check voltage on Tan wire to ground it should be +5 volts. ECM internally uses identical circuits for input signal conditioning - 1k pull up to + 5 volt with 10 k in series going into U11 A/D converter. If both are reading +12 it maybe that ECM is hosed or you have oddball ECM??.

Here is a thought - disconnect ECM from harness, turn key on - measure yellow wire at CTS. If 12 volts is present then you got 12 V harness short to CTS line!

Which ECM do you have - is it 1228747???

You can always get used ECM from JY for about $40. There are no cheaper after market alternatives. BTW, do you have to pass sniff test?? If so factory ECM is your only alternative (for now).

In my neck of the woods (Orange County, SoCal) local JY's have 50% sale during labor day weekend! It is the best time to stock up on ECM's and other disposables. Just make sure you know which ECM you have.

//RF

 

hmmm, still having trouble getting data logging

I got the usb-serial adapter and made the cable according to the winALDL website (had to use the car as a 12V source since the usb adapter doesn't have 12v), and connected it up.

WinALDL sees my serial adapter, I set the right com port and ecm model # from the list on their site (1228746)

But I'm still not getting any good data, winaldl shows a small amount of data in the raw data section, but nothing really useful, none of the other tabs show anything useful (still all zeroes, even in the "dash" section)

I've cycled through the list of supported ecm's, as well as tried the 10k resistor from pin A to B, still nothing (just small pieces of random data)

I've like triple checked the connections too

Anything obvious I'm missing? or is the ecm hosed.

 

M4xx

In WinALDL, under com port settings, select 4800 baud. For some reason default is 2400 baud.

//RF

 

Yeah lol I finally saw that baud setting in the config menu, i feel like an idiot now


I haven't measured the raw resistance on the TPS yet, but I'm like 99% sure it's the sensor that's bad (at idle TPS is 0.16 volts, then barely touching the gas makes it drop to zero, then it jumps to 4.8v at WOT). Time to go test the TPS

As for the CTS, raw value is pegged at 255, even when grounding the sense wire (should make it go to 0). Either faulty wiring or a bad A/D converter in the ECM.

And the engine is running silly rich, since with the CTS sensor bad there's no way to get it into closed loop

I'm gonna check the cts wiring tomorrow, as well as the tps, and replace it if necessary (do auto parts stores like autozone still carry this?)

 

Yeah, Vato Zone should have the CTS and TPS sensors available no problem. CTS is pretty cheap. The TPS is probably gonna be about $40-$50. Those don't go bad too often on the TBI cars, so if you're on a budget, you can always snag one off a TBI car in the junkyard. I noticed nobody ever answered your question about the melted black cable by the washer fluid jar. That's probably your cruise control cable. It's a long azz cable that runs from the actuator, which is located by the washer fluid jar, and runs to the thottle linkage. Also, the reason your blower vents only stay in one position is probably a broken or melted vacuum line. There's a vacuum line that runs from the back of the intake manifold and through the firewall. It supplies vacuum to the selector control for the air ducts. Since you had a fire by the brake booster, there's also a vacuum line in that area for the cruise control actuator that might've gotten melted. So check all your vacuum lines under the hood to make sure they're still intact. They're hard plastic in some places, and rubber in other places. It's really common for the hard plastic lines to get broken or melted. Vacuum leaks could also be contributing to the motor running rough and too rich. Speaking of which, make sure the vacuum line going to your MAP sensor on the firewall is in good shape too. It gets vacuum from the same fitting on the intake manifold as the duct selector switch.

 

Yeah ok I was wondering what that thing was, I figured since it pulled open the throttle it was either to raise the idle speed when the engine is cold or for cruise control (or both)

This piece doesn't really seem necessary, can it be removed without the ecm throwing a code? I'd rather just take it off and save the weight than spend money to fix something I don't really care about too much.

And yeah I noticed the damaged vacuum lines, and replaced them. A/C vents work now

 

All right I fixed the CTS, some idiot cut the cts sense wire and spliced it to the cooling fan relay, disconnecting it from the ecm (that's why it read 12V and grounding it would turn on the fan, lol)

I hooked it back up like it's supposed to be, and it works! Checked it in winALDL, code 15 went away and the temp. was at 78.5* (ambient) then steadily rose as I let the engine idle.

The TPS seems to be dead though, it needs to be replaced. Wiring on it is good though.

 

M4xx

Step by step - cooling fan to CTS now thats a classic one!
Cooling fans have their own sensor (I think) switch which they run off.
Through my trips to JY I have bought a collection of sensors. Just bring a small DVM to see if they are alive.
My local JY charges $2 for most sensors. MAP sensor reguires a DC voltage - I use 3x AAA in a holder together with couple clip leads and small vac tube. Suc on it (tube) and observe voltage go down from 4.2V.

Let us know when you get TPS R&R - also get dataloging going for further trouble shooting.

We'll have to address cooling fans control circuit soon.

//RF

 

All right just got back from autozone, got me a new TPS, it was only $25. Works perfectly

So, the ecm shows absolutely zero error codes now, engine runs a lot smoother with all the sensors working, plus the mixture is a lot more accurate

far less smoke, but it's still in open loop, and I just reset the ecm to clear all the codes, so I can't really blame it.

Still got to change engine oil, tranny oil, fix coolant leak, inspect the brakes, and get a new tire before I can take it for a spin, but I'm REALLY close now

 

M4xx

Looking good there , but you still have a lot of work in front of you.

Coolant leak - how many mile you have on your old girl? Chevy OEM water pumps can last up to 120k, while most begin to leak at about 70k. It is not that difficult of a job except you have to take a lot of crap out of the way to get to it. Plan on spending 3 to 4 hours, make sure that you have tools. Swearing a lot helps, so as long as old ladies and little children are out of the hearing range.
Cooling fans - I suggest that you do a quick search here for a schematic. You may want to take care of fans before driving.
Tranny filter and fluid - take a close look at color, and smell it. Brown and burnt odor can be a bad sign. Replace a filter, take a look at sediment at the bottom of the pan. If the filter has not been changed in while there should be some brown looking crud, large metal flakes - not a good sign. Clean it all out (Simple Green works great). Do not over torque pan bolts - an all too common mistake and cause of many leaks.
Open loop - get WinALDL going in data log mode. Keep an eye on O2 sensor transitions as engine warms. O2 voltage will be steady at first around 450mv while engine is cold. O2 sensor must be heated to about 600C before it starts reporting O2 concentration . Once O2 starts to report you should see swinging O2 voltage (120 to 850 mv).
The following is my personal pet peeve - if you ever have to replace your single wire O2 (Delco AFS-21) replace it with a three wire heated version GM# 25176708 or alternative Delco AFS74.
http://www.sethirdgen.org/HO2S.htm - ignore prices, Google it. I run headers on my rig and heated O2 is absolutely mandatory.

//RF

 

Coolant leak: it's just a cracked thermostat housing, my girlfriend's dad is giving me one, one of his friends used to have a bunch of third gens

The cooling fans work fine, I have no clue why one of the previous owners spliced the CTS to it

Tranny: I tried to drop the pan today, three of the pan bolts are above the crossmember so that was being a pain, put a jack under the back of the trans and tried to remove the crossmember, broke my ratchet (popped the gear, it just spins now), and found out that the tranny mount is broken

I got a new tranny mount and a bigger ratchet (autozone had a solid poly mount, looks pretty nice and has a lifetime warranty)

so I guess I'll find out tomorrow if the tranny is any good, if not I think I'm gonna go try and find a cheap T5 or T56 and clutch assembly and do a MT conversion, I really want a manual in this thing

If I were to get a tranny from the junkyard, are they easily rebuildable? I've rebuilt motorcycle engines/transmissions before, so "easily" is relative.

 

When doing AT to MT conversion do not forget all the other stuff such as pedals, slave cylinder, plumbing, etc. Also, ECM will have to be updated with MT code.

Rebuilding manual trany will require specialty tools. Suggest that you look at the expense before starting this undertaking. See how far you can nurse that 700R4 for now. Also, you have sniff test in front of you - that will be a big undertaking.

//RF

 

Yeah I've read the tech articles a few times on the MT conversion, if the 700r4 is dead I'm probably going to go that route instead of spending the money to fix the auto when I'll just have to dump more money sometime in the future to do the conversion at a later point, may as well take care of it now since the car doesn't work anyways, take some time to save up the cash, do it once, and do it right. As I've said earlier, I don't really NEED the car, it's just a fun little project of mine, so I can go see my friends and stuff, I walk to campus and work, and take the bus everywhere else since it's free for UT students

I'm pretty confident I can get it to pass the sniff test, all the emissions equipment is present and functional as far as I can tell, the ECM appears to be good (havent gotten it into closed loop yet, that will be the final check, then do some datalogging)

Well my next class is at 2:00, so I'm off to go work on the trans

 

All right I got the crossmember and pan off

Figured out why the tranny wasn't working, it barely had any fluid in it, just up to the level of the pan gasket (had a pretty serious leak from the pan gasket, there was black crud EVERYWHERE under there, lol)

Tranny itself appears to be ok, the remaining fluid in there was still a nice red color, no burnt smell, no chunks in the pan, just about a 3/16" layer of metallic paste on the magnet. I cleaned all the black crap off the pan, cleaned the mating surface on the tranny really good, replaced the filter and reassembled, lubing the new gasket and torquing the pan bolts to the proper spec.

Refilled with fluid, so far there don't seem to be any leaks, but I haven't started it yet, waiting for my new thermostat cover.

I went ahead and took the old one off, there was a bunch of gel built up behind the thermostat and in the top hose. Looks like someone mixed antifreeze types or something. Is there something I can add to the coolant that will dissolve any remaining gel??? How serious is this? I don't want to have overheating problems later on

 

If it's not very deep into the hose, it might be a "hose lube" that they sell at AutoZone or Checker/Schuck's/Kragen. It's s'posed to stay gelly for nigh on forever. If it's not, run the car with some flush in it. There's two kinds of prestone flush, one that you run for 6-8 hours of normal driving, and the other which you run for five to ten minutes THEN DRAIN THE WHOLE SYSTEM. I'd recommend the first one, then the second one, drain, fill with water, rust inhibitor, and re-run the first one. Then depending on how cold it gets where you are refill with Water, Rust Inhibitor, and Water Wetter, or your usual anitfreeze mix.