1991
CAMARO
305 TBI AUTOMATIC


What occurred: I wanted to adjust the timing, for some reason it keeps getting itself out of timing, so what I did was loosen the distributor bolt and unplugged the EST cable and the car NO LONGER STARTED!!! it turned over and fired up then quickly died, after numerous attempts and hours later we left the car sit for a bit, I then sprayed starting fluid in the plenum and it started right up as if nothing had happen' I then let it warm up for about 3-4 minutes with the EST cable plugged in. I then unplugged it FIRED UP and instantly dies due to lack of fuel. I then plugged the EST cable in and it still didn't stay on idle, just kept turning, what the hell is wrong?

Potential Problems Checked out:
Fuel Pump Relay Working (SWAPPED the relay from the blower)
Checked E.C.M. fuse and FUEL PUMP fuse, both OK
MAP SENSOR GM NEW
INJECTORS ARE NEW REPLACED 10 MONTHS AGO
IGNITION COIL REPLACED 1 YEAR AGO AS WELL AS IGNITION CONTROL MODULE
NEW CAP AND ROTOR
VATS HAS BEEN DELETED FROM COMPUTER SO IT IS NOT A PROBLEM
OXYGEN SENSOR REPLACED 2 YEARS AGO

Symptoms:
INJECTORS DRIPPING FUEL INTO PLENUM
Injectors cutting off fuel, seems to be dripping fuel into plenum
SERVICE ENGINE LIGHT IS ON BUT HAS ALWAYS BEEN ON


What the hell else could I do?? I dont think it's the fuel pump since it's getting fuel (dripping) but then cutting off.

 

91Camaro

You said that you have unplugged EST connector - do you mean that you have unplugged 4 wire connector??? In order to set timing all you have to do is to unplug single wire EST set tining connector (brown-black stripe wire).

//RF

 

thats exactly what I did, I unplugged the brown black stripe wire and then set the timing and turned the car back on and it would not turn back on. Just a few hours after the first post I did. I went outside and put the key in the ignition and turned it and it FIRED UP!! and stayed idle ling I then set the timing and turned off the car plugged it back in started it up and it fired right up and started. I then looked at the degree reader and the line was about an 8th of an inch to the passenger side away from the degree reader so I turned the car off and tried to start her up again and she didn't fire up!!! what the hell is going on???

 

'91 Camaro

Lets get some background info on your Camaro - how many miles, mods, etc. 1) It is possible that you may have a timing chain that have stretched over the many years and as a result you have unstable timing. Take of valve cover off, pull all plugs, with a breaker bar and proper socket turn crank shaft back and forth and see how much free play you get. Observer rocker action -there should be very little free play.
2) The other possibility is that you may have worn distributor gear. This typically happens when a wrong material gear is used with roller cams. Check amount of backlash or pull dizzy and check gear for wear.
3) Another possibility a loose outer ring of the harmonic balancer.
All of the above will give you 'funky' timing and screw things up.

//RF

 

The possibility that the timing chain might be stretched is very close!!! I checked the distributor gear 1 year ago and it looked fine. The mileage on the camaro is 144446 NO MODS on the camaro, except deleted AC DELETED AC PUMP and DELETED VATS. The problem that I see is that the injectors are not throwing out fuel when I turn over the engine, I just changed the ignition control module to the original GM one, still nothing. I will try to start it tomorrow.

 

'91 Camaro

Injectors will discharge fuel only if ECM is receiving a reference pulse from dizzy. Before you start digging into dizzy to ECM harness check injector fuse - it is not unusual for fuses to go. Disconnect injectors, with DVM check red wire - it should read +12 Volts while cranking. If not, check fuse and broken wire harness.
ECM fires injectors by pulling drk-green and drk-blue lines to ground - this also can be checked with a DVM or test light. You should get pulsing light while cranking. No pulsing light may mean that ECM is not receiving reference pulse from dizzy or in a worst case the injector driver chips are shot. Do the simple checks first.

//RF

 

Checked out the ECM Harness, plugged in my multimeter in terminals D15 D14 AND B5 all checked out ok, im getting normal readings from all of them. It seems like everything is working fine. I do get a SERVICE ENGINE LIGHT, but it was on for years could it be now that, the very reason that light is on is the actual problem and has now taken it's toll? I don't get how the car sometimes starts randomly....

 

'91 Camaro

Ok lets get the gremlins out of this thing one by one.

1) I know you checked operating voltages at the ECM D15, D14 and B5. What about at the injector connector itself? if you have a broken wire in the harness the voltages at ECM (D15 and D14 will be OK) but injector will never be actuated! You got to be very disciplined while troubleshooting.

Check Pin B5 - it should be less than 0.5 (dizzy reference ground)

SES light - what exactly is it doing under the following sequence: key-off; key-on engine-off?

//RF

 

I had a 89 camaro 305 TBI do this once. however it did one thing you haven't mentioned just before the injectors stopped spraying there was an extremly strong odor of fuel. and after it died when I removed the gas cap immense pressure came out. After the car cooled down for awhile it would start right up.


Aside from the fuel odor it did everything yours is doing. I replaced fuel pump same thing.

disconnected purge line from fuel tank didn't do it as much. however much stronger odor when it did it.

ignition module, new injectors, coil, etc. still did it

then I found the ground wires on the back of the cylinder heads were loose as well as the ground strap that goes to the firewall. I tightened the grounds on the back of each head and ran a small nut & bolt through the firewall and sanded the paint off to bare metal before attaching that ground strap. I also pinched the injector connectors so they got better contact.
After doing this the car never did it again. Maybe not your problem but just a thought.

 

I also forgot to mention, like yours when it did this the injectors would occasionally drip fuel. However pour a little fuel into the throttle body and it would fire up right away.

One person explained to me with these grounds loose it basically causes the injector drivers to overload and shut down. and that is what was causing the massive odor of fuel. Not really sure if he was blowing smoke or not on this reason .... maybe someone else can tell you if this is fact or fiction .... seems kind of logical though. Why my tank built up so much pressure not sure maybe related to the ecm not being able to purge the tank due to the bad grounds as well.

 

Things attempted this morning:

Charged BATTERY
Connected pin A and B to find out codes, kept on flashing code 12 over and over and over
Swapped MAP sensors still nothing


When I turn on the ignition the SES light shows up right away, but when the car is on idle it takes a few seconds to turn on and it stays on.

A few moments ago I walked out and turned the gas cap to it's venting position and to my suprise it hissed for about 20 seconds which was really wierd. Earlier me and my friend were trying to start the car while the battery was charging. We sprayed carburator cleaner into the plenum and when I went to start the car a big fire ball shot out and the plenum was on fire, the car did not stay on idle. The following attempt the vehicle backfired. Also it sounds like it really wants to start but as soon as the injectors stop dripping there is a loud BUZZ coming from that area and the car does not idle and dies.

I will clean all ground wires right now.

 

Nothing..... it wont stay on idle no fuel coming out either, I can't even hear the fuel pump humm because the car is out doors and it makes that stupid default key sound........ I don't know what else to do with this

 

yea 20 seconds of hissing sounds about as much as mine did it. that and the fumes while it was hissing could kill you LOL ..... I remember one other thing I changed as well. Theres a sorta white looking vent/valve coming from the fuel lines back by the tank. I think its some sort of a pressure relief valve not sure though, I changed that as well.

try starting it with the fuel cap off, mine would usually start like 15 minutes after venting the tank.

 

'91 Camaro

Code 12 No reference pulses to ECM. But read on..

This code should flash whenever the "test" terminal is grounded with the ignition on and the engine not running.
If the engine is running and the code appears, this indicates that the ECM is not receiving any references from the distributor. Faulty or loose EST connector at the distributor is typically a cause for this code.

Keep in mind that the ignition must be OFF to reduce risk of damage to the ECM. Once the terminals are shorted, turn the ignition to the ON position without starting the vehicle!
The "Check Engine" light will begin to flash a series of codes, the first one, code 12, will consist of one flash, followed by a short pause, and then two flashes in quick succession.

Each code repeats 3 times before the next code is displayed

Once all of the codes have been displayed, the ECM will start over the sequence with code 12. If no codes are stored, code 12 will repeat until the ignition is turned OFF and the jumper wire removed. Once you see code 12 display for a forth time in a row, you can safely bet that no additional codes have been stored.

Solid SES light - hmmm - I got to look this one up in my service manual. Limp back mode due to missing reference pulse???? I do not know right of the top - got to look up.

Lots of hissing from gas tank means that you have a lot of vapor in the gas tank. This could be due to old gas leftover from winter months or clogged charcoal canister filter. That's an easy check.

Do not dump too much gas into TBI. I use a little bit of WD-40 - just as effective and can be easily controlled from a spray can.

 

Thanks for your help both of you, I was consulting one of my buddies from Texas who helped me find problems, we found it.

At first I measured the Resistance on the fuel pump by contacting my multimeter probes to the plug terminals from the fuel pump (located on top of the differential) I contacted the black with black and red with the grey wire that gave me a resistance of .909 K ohms which was weird. So I then grabbed a charger and connected it with some wires to the fuel pump plug and gave it a quick boost 12v I really couldn't hear the pump prime since the noise of the charger overcame the fuel pumps noise. I then was stumped and decided to remove the wires and plug it back up, keep in mind the rear of the camaro was up on jack stands and there was less than a quarter of gas remaining in the tank. I then asked a friend to go inside the car and turn the key in the ignition on the ON position to hear if the pump primes, I asked him to close the door so I would not hear that ugly default key sound. He turned it on and I HEARD THE PUMP PRIME!!!! I then commanded him to turn on the engine, it FIRED UP as if nothing was wrong!!!!! it stayed on IDLE I let it idle for some time to warm it up, I timed it, BOLTED the DISsy, PLUGGED EST CABLE BACK UP, and the car fired up nicely! The car being in my friends drive way, I asked if he had any fuel I could put in my tank, he said all I have is 103 Octane fuel,him that'll work so we poured some in until I got at least a quarter tank. So it had to be 1 of 2 things or both, Pump was stuck with little gas, or wiring was dirty!!??

 

Your pump was probably locked up. They way I like to test that is to hook it up to power backwards and make the pump spin the wrong way, incase there is some blockage. You may have done just that and cleared some blockage from the pump or got the pump to spin out of a dead spot or something. I would consider replacing the pump. Esepcially it if starts acting like this again. You should probably check the tank for contamination anyway and then throw in a pump while you're in there.