I recently acquired a one-owner 1991 Camaro RS from the little old lady across the street. (no kidding) Her current husband said it needed a fuel pump and she was tired of putting money into it. So I bought it to fix up for my wife. I verified the fuel pump was bad, and replaced it. The FPR checked out ok, as did the rest of the circuitry. (I ordered a 1991 Dealer Service Manual on Ebay and am using it). I have fuel pressure at the schrader valve (sprays up to the raised hood) on the fuel pressure test connection on the rail. (3.1L MPI) We can hear the new FP run for 2 seconds when the key is switched to on. The engine will not start unless ether is used. Then, as soon as the ether is consumed out of the intake manifold, the engine dies. This can be repeated several times, yet the engine will not run. I am thinking there must be something going wrong with the injectors or the circuitry controlling the "firing" of those injectors. Has anyone experienced this or has a hint as what I should look for or do next in my attempt to make this vehicle something besides a lawn ornament? Please advise if you can. Pretty red RS Camaro would look really good if I could have my wife sitting in it with it running! thanks in advance for any assistance.

 

You need to actually test the fuel pressure with a gauge.

Ohm the injectors to make sure they're good and that you're getting an injector pulse.

How many keys do you have? It's possible the VATS is causing an issue. It's possible the resistor in the key has gone bad or the sensor in the ignition itself has gone bad.

 

Ozz, thanks for responding. To address your hints, FP is 42 psi gauged. The engine will start and run as long as fuel is supplemented to the air intake at the Throttle. I have traced all wiring and fusible links. All check ok. No broken wiring, no shorts, etc. I am thinking it has to be the injectors not opening (for whatever reason) I have a tester and am going to check and see if I have a pulse to the injectors while cranking. If not...then I go to the next step on the chart in the 1991 Dealer Service manual for the Camaro RS i bought off Ebay. I was hoping somebody had an idea of where to go next. (after checking injectors) If I get a pulse, I will ohm them and see what's up with that. Thanks for the hints.
UPDATE: 12:52 p.m. EST
Checking circuit that connects to Drivers Side Rear Injector (easiest to get at) Constant Power to injector connector with KOn (checking from pink wire to ground) , NO PULSE when starting (checking with test light between contacts on injector connector, pink and green wire) Could it be anything besides the ECM?

 

It's possible the injectors are gummed up and aren't firing right. You might want to go ahead and replace them while doing your tune up (plugs, plug wires, cap, rotor etc) just to ensure they're good.

 

Does the car like just die, like now. Or does it seem to run out of gas?

 

car starts when ether is sprayed into throttle body/manifold. dies immediately upon cessation of ether introduction. Following flow charts in the service manual, I am understanding I have a bad ignition module in the distributor. There are additional flow charts to determine if it's the module or the pickup coil, but I'm just going to replace them both, and be done with it. My thanks to you and Ozzy for responding, I'll let you know how it goes once I install the new components. *wish me luck!

 

hang on... the ignition module controls spark.
Since the starting fluid is burning you have spark.

Am I missing something here?

Did you check/test the injector fuses & ECM fuse on the main fuse block?

Otherwise I believe the injector firing is controlled by the injector driver which is built into the ECM not the ignition module. BUT I could be wrong perhaps the injector driver needs a signal from the ignition module to fire the injector in time with the spark plug but that would mean you have sequential port fuel injection ? not batch fire or "multiport" FI

 

to ensure you don't have blockage at the fuel rail did you loosen the return line to see if fuel is flowing back to the tank?

 

THanks for your response FRMULA88. In reply, The first thing we (my unemployed son with a aerospace engineering degree & I) did was to replace the fuel pump since it was obviously bad. Upon R&R, it appeared to the the "original" fuel pump. As soon as we energized the new pump, we could hear air bubbling into the tank from the return line while the pump was running (two second pulse from Kon). Also, the service manual states the ECM needs a "reference" signal from the ICM in the "Dizzy" in order to know when to "fire" the injectors. I have been following the "diagnostic flow charts" in the original 1991 Camaro dealer service manual I purchased off Ebay. As a by-the-by, if anyone needs to know "almost anything" about the 1991 Camaro series, message me and I will look it up in the service manual, up to and including scanning the particular page(s) necessary, if it does not require a voluminous response. Just my way of "paying it forward" for all the help I'm going to need as I attempt to "restore" this beautiful vehicle to as good a condition as my wallet will allow. :P
As to "Did you check/test the injector fuses & ECM fuse on the main fuse block?" Yes, and the 20 amp fuse over the right fender and the fuse block and I also "rang out" the FP relay, etc, etc, since I started trouble shooting the "no run" condition. But thanks again for the suggestions, they were good ones.
By the way, I noticed you are an Architect/Construction manager. I also was a Construction Manager/Commercial Construction Superintendent before my old back gave out on me. That sorta makes us "brothers", if not like-minded individuals. "Pleased to meet you", my friends call me Jim.

 

Jim,

Been awhile since I had computer controlled timing in my car.. LOL. You are correct the ignition module has 2 weather pack connections; one goes to the ECM (to control the timing) the other goes to the coil to energize the module if memory serves me correct.

Did you inspect / test the wiring from the ICM to the ECM for any damage / shorts to ground ?
Did you check the weather pack connection for corrosion the module for corrosion on the pins? sometimes contact cleaner and dielectric grease will fix the problem.

if that all checks out let us know how this turns out after you RR the ignition module.

When replacing the module be sure to clean the mounting pad on the dist. base and apply the dielectric lubricant that should come with the new module otherwise it will burn out and you will have to redo it. clean and grease the connector as well.

Otherwise you did all the diagnostics, plus it is good you have the factory service manual as a guide.

Nice to see an original car ( sounds like it is mint condition) get back on the road and be enjoyed.

p.s.

If you have not done it be sure you replace the fuel filter, if the pump was original my guess so is the filter.

A clogged filter may show you have adequate fuel pressure, but not enough volume of fuel.

 

Formula beat me to it. The next step I would have suggested is the filter. Formula88 has some good ideas on what to check. When my module went out and the car just died on the side of the road. Wasn't giving me any spark at all.

 

My reservation is since the engine is actually running on the starter fluid this means you have spark (ignition).

Call me old school but if you have spark, and you have air, and it runs on the ether, to me means you don't have fuel.

The injectors are not passing fuel.
replace the fuel filter if you have not done it already.

I find it odd that only the half the module (the ECM signal to fire the injectors) would fail.

This is a solid state part, either it works or it does not, which is why I suggest inspecting the ICM to ECM connection and the wiring before assuming the part is bad and replacing it.

If you unplug the harness at the dist. and see white / green residue (corrosion) or missing / broken pins on the issue is most likely a poor connection. if the pins on the module are missing / damaged you have no choice but to replace it. if all this checks out.. then replace the module.. if you still have the problem then it is the ECM.. which I find odd if the service engine soon light is not on.

DID you check for any trouble codes? if you try to test and the SES light does not come then you are heading in the right direction. since the fuel pump is priming odds are the ECM is OK, or is it? Do not rule out anything.

 

I pulled up a v6 diagram

test the DK Blue and Dk green wires when in key in run or start. These are the feeds to the injectors off the ECM. Pins C12 & C11 on the ECM harness plug.

if these test OK, then I don't think the ESC module or ECM is at fault.


Did you check the PASS Key module / wiring ? Again it's been so long I don't remember if this simply dis-ables the starter or disables the injectors but the check pink & black wires.

If you are getting power to the injectors and the PASS key wiring & key is OK and you replaced the fuel filter, then you have a restriction in the fuel line (possibly upstream of the filter) or bad (clogged) injectors. if you replace the filter and notice a lot of debris in the line.. I would disconnect the supply line from the fuel rail and try blowing the line clear with compressed air to make sure you can do the same with the fuel rail.. sometimes this is enough and when proper volume of fuel is restored the increase flow will get the injectors to fire.. once you get it started get a high quality injector cleaner..

 

I am really appreciative of ALL THE GREAT responses. I've been chasing my tail for almost a week with this. I do not have a scanner, but i followed instructions and "grounded" the contact in the diagnostic link under the instrument panel and the SES blinked out a code 12 (twelve). No reference signal to the ECM. I replaced the Ignition module and still no joy. Only thing left is the pickup coil as I didn't want to pull the dizzy just yet if the Ign module was going to solve it. Since I am disabled and on a fixed income, looks like I am going to have to cool it for awhile, after this last thing. I still have a new pickup coil to try so.... Looks like I gotta pull the dizzy. Oh well, I'm having fun, aren't I? Please tell me I'm having fun....

 

CODE 12 means the ECM is working.. code 12 will flash three times then it will spit out any trouble codes in sequence.

If there are no other codes, Code 12 will flash until the diagnostic jumper is disconnected or the engine is started.

see this link... it is for the Grand National but all ECMs from that vintage operate on the same principle and throw the same codes.

http://www.gnttype.org/maint/malf.html

 

http://www.iroczone.com/2009/10/1982...maro-firebird/

another source..

Code 12 with Key on is normal.

Code 12 with engine running is NOT normal..

Compare to the code list for the GN link I sent and you will see they are similar..

I think whatever information you have is poorly written.

Again because the car will run on starter fluid I am more inclined to think you have a fuel delivery issue not a spark issue, especially if the ECM only throws a code 12.

if the spark plugs are firing ( to burn the starter fluid) the Ignition module / distributor should be fine...

I would be replacing the fuel filter, cleaning the fuels line and fuel rail, & check the fuel pressure regulator..

last resort if the injectors are getting power is replacing the injectors.

 

Here's what you've said:
- Starts / runs on ether (so you have compression and spark at the right time)
- You have good 42 PSI fuel pressure at the rail (you have fuel pump working and getting fuel to the rail)

So that means there is only one thing between getting fuel from the rail to the combustion chamber - that's the injectors - they're not firing. SO pull 1 of the plugs on each side, test the pink/black wire for +12v with the key in run/start - if you get 12v there then you have power to the injectors and the only thing left is the ground signal from the computer - let's for now assume the computer is good since you got the self-test OK signal from it. There are really only 2 things that could cause it not to fire off - that's the pickup in the distributor is bad (or the wiring) and the TPS (if it thinks you're WOT it goes into anti-flooding mode and quits firing fuel into the cylinders. My bet is on the pickup in the distributor being bad.

Test those and get back with the results.

 

IF the TPS were bad it would have thrown a code.

are we having fun yet ?

 

I sprayed a 125 shot thru my stock 305 for years.

because it was a mild 8.5:1 compression TBI engine I simply used premium fuel and a colder spark plug. after a few runs I put the timing back into .

 

Not necessarily - if the battery was dead/unplugged for a while the codes would have cleared and wouldn't show a code immediately - I admit it's a long shot that's why I said to check the other stuff first.

 

After all this great advice, I have come to one conclusion....All of you have forgotten more about this car than I will probably ever know...:P With that being said....I have now only two things left, maybe three, the pickup coil in the dizzy is bad and/or the injectors have "gunked up" and will not allow fuel to spray out....and/or the little girl thinks I have my "foot through the floorboard" and have flooded the engine. Therefore she "ain't givin me no mo juice till she thinks she needs it"...I'm referring to this engine as a she now...that is because I have surmised that she is a B*tch! Oh well...when I feel up to it again, I'm going to pull the dizzy, replace the PU coil, R&R the injectors with new/rebuilt ones, R&R fuel filter, ...it none of this works, i.e. the bitch won't run.....I'm taking her to a REAL mechanic and say "I give up....YOU make her run!" ...and many, many, many sincere thank yous to ALL of you kind hearted and patient folks who gave me such good advice. Muchos Gracias BTW....I ordered the injectors from Southbay...

 

do it step by step... don't waste money on new parts you don't need.

DO THE FUEL FILTER FIRST if you replaced the fuel pump, you should have replaced the fuel filter at the same time.

if debris comes out of the fuel line when you replace the filter, you found an answer. Try to start it with a fresh filter .. if no go then my money is on clogged injectors. Again if the engine starts on ether you are getting spark.

before you clog a new set of injectors clean out the fuel line or replace it.

Once you get it running

My guess is the fuel tank is full of junk, I would be checking iit and replacing it or get it boiled out before you ruin another set of injectors.

 

The old girl had sat for awhile and we removed all the old fuel when we replaced the fuel pump. (there was a lot of junk and small "divets" of rust had started forming on the FT walls above the "liquid" line. All else being normal, I went with "bad" injectors and ordered a new set from Southbay. While waiting for their arrival, I went ahead and pulled the old ones. GOOD GRIEF! I was able to "tap" lots of "crap" out of them all! I think that was the problem. New ones arrived yesterday afternoon and I am going to try and install them this morning before it rains. (I am working under the sky). I am almost 99.9% certain the ol' B*tch is going to run before this day is out!!! Oooweee!!! I'll let ya know how it goes. Thanks again for all your help and advice.

 

My guess is the previous owner never stored the car with a full tank of gas.

Guess what? as you fill up the tank with fresh gas and drive all that debris in the tank that was above the fuel line is going to mix with the fuel & gunk up the sock at the fuel pump pick up. The smaller debris will gunk up the new fuel pump & filter, the rest will screw up your new injectors.

Boil out your tank or buy a new one.. it will be cheaper in the long run than replacing the pump and injectors a 2nd time or your wife getting stranded on the side of the run with a car that quit running.

When you store the car for the winter (or more than 6 months) be sure to top off the tank and add a stabilizer. My car sat for 18 months and fired right up.

The full tank prevents condensation from forming in the fuel tank and rusting it, the stabilizer keeps the fuel from going bad. A lot of members like seafoam.. but I have always used Stabil (the regular old red stuff) and never had a problem even with 10% ethanol blended fuel.

 

Guys, I'm really stumped. Nothing has worked. Car still will start and run GREAT, as long as you supply the throttle body with starting fluid. I installed the brand new injectors from Southbay. The problem persists. Even though the ECM shows a Code 12, I found another one from a running vehicle on Ebay and it now sits in my hand. I will install it in the morning (later today as it is 2:50 EST as I write this) I have been a "shade tree" mechanic since the 70's. I have never been as clueless as right now. I have rebuilt engines, swapped engines, repaired practically everything I have ever owned and driven over the last 40 years. I have never been this puzzled over why an engine won't run. I have looked for shorts, broken conductors in the wires, fuses, connections, replaced the ignition module, installed a new fuel pump, verified fuel pressure (42 psi) at the rail, flushed the fuel lines, flow tested the fuel pump. The engine is getting "fire", because it will run with starting fluid. For some reason, unknown to me, the injectors are not spraying fuel into the manifold. I have followed the "trouble shooting" diagrams in the 1991 Camaro Dealer Service manual I purchased of Ebay. Every Time it leads me to "possibly a problem with the ECM". We are going to find out. If it will not run after a known good ECM is installed, I humbly await any further ideas this community might have as to why can I not find out what is wrong with the car. Thanks again for all of your knowledgeable advice.

 

have you verified fuel pressure while cranking ?

if fuel pressure drops while you are trying to start the car you have narrowed down the problem to a bad fuel pump, fuel pump relay, or the ECM.

it may be the ECM allows the pump to prime so you see fuel pressure at the rail. . but when starting the car the pump may not be not running, so the engine is not getting fuel..

Like I said if the engine runs on starting fluid, you have spark

 

Hey Formula, I had to get away from the Camaro for a while, before I went looney tune and started hitting things with big hammers. I am thinking the problem must be the vats. Everything works, no codes, running with supplemented fuel due to injectors not opening. Something so simple yet complicated when it is outside of your experience. I have never before owned a GM vehicle that had the Passkey VATS. Anyway, I ordered the VATS bypass module from Baker Electronix that is supposed to fix the VATS issue. Enable the Starter and send a 5V signal to the ECM so it will allow the injectors to open. Now all I have to do is figure out how to install the dang thing! I removed the kick panel from under the dash and just lay there for a minute until I crawled back out. WOW! there's a lot of wires under there! How in the world am I supposed to find this circuit 229 or whatever? Does anyone have or know of a photo that would show me where to look? That would help greatly. I feel like I'm close, like this is gonna do it! So if someone could please point me in the right direction, I can take it from there. Thanks.

 

Yes.. see my post #13 " Pass Key" .. "VATS" same thing. I would have assumed you tested that before you went any further.

The problem usually is you might be using a spare key that does not have the chip on the side to disable the VATS.

It has been waay too long for me but I recall the VATS module is a little black box (behind the driver's side kick panel) I believe the yellow wire (or purple) from the ignition switch goes into it. I had to replace the harness on my car years ago . the one I got from the junk yard had VATS... I just cut out the module and spliced the wires together, problem solved. but my '88 did not have VATS from the factory so there was no issue doing this.

Otherwise you can search on this site for VATS disable and there is plenty of information with diagrams.. your service manual also should have the wiring diagram

 

Well, I must be going bonkers. I double checked the manual on the VATS and following the key on/bulb test it says the VATS accepted the key. i.e. the Security light went out after about two seconds. I replaced the ECM with a known good one this morning and the d*mn thing still won't start! The ONLY thing I haven't replaced is the pickup coil in the dizzy. That's next. It that doesn't work....I give up. It must want another home. Good Grief Man! I have never been this befuddled over an engine not running in all my life!

 

well, If that is the only thing left to replace you know what to do. Hopefully once you get it running you can return the spare ECM you bought.

Now you know why some people remove all that and convert to a carb with HEI ignition.. unless you understand all the electrical components EFI can be a huge PIA when it breaks down.

curious did the "new" ecm also throw code 12 ??

 

After a short sabbatical, I rolled up my proverbial sleeves and jumped back on the Beast!. It was the pick-up coil! I stabbed the dizzy about 20 minutes ago, hooked all the vac hoses back up, connected the battery. She hit after about 2 revs and lurched (like timing was a little early). I dialed it back just a touch and she hit INSTANTLY and RAN! Hallelujah! There is a Benevolent ONE above! I take it all back. She's not a b*tch, she was just mis-understood....:P lol Thanks for all your help. It was appreciated. Especially having a sounding board for my suspicions.
BTW, I never checked the codes on the "new" ECM. I put the old one back in along with it's Mem chip. (so everything is as it was before I replaced it) ...and, I think I'll just hang onto that extra ECM....you never know what might go wrong next!?

 

Great news, now your wife can enjoy it !