90 Vette quits running when warm

[asby69]

Hi all, my 90 vette, L98, started acting up on me a few days ago and I'm stumped so I'm turning to you (my friends) for help.

It runs fine after the morning start up for 8-10 minutes and then the engine quits. It stops and will not start back until I let it rest for 10 or so minutes. After it sits for a spell, it starts back up and runs fine for a few minutes then back off again.

If I try to start it up right after it quits, I can get it to start but it's like the engine is "flooded" with gasoline because it smokes black and misses something terrible. If I don't keep the accelerator pressed basically to the floor it'll stop running.

Any ideas on where I need to start?

THANKS Guys & Gals.

Asby69

 

[G Winter]

My first thought is fuel pressure regulator. Be sure the vac. line is hooked up and not broken anywhere.Check the fuel pressure. From here I think someone else will chime in soon .
Glenn

 

[asby69]

Thanks!! Ok now, where is the fuel pressure regulator?

 

[G Winter]

Thanks!! Ok now, where is the fuel pressure regulator?

The regulator is at the back of the injector rail in the crossover,under the plentum. You can check the pressure on the fuel rail.The pessure should be 41-47 psi. But you need to trace the vacuum line to make sure it don't leak.

Glenn

 

[asby69]

What is the best tool to test the pressure?

Thanks again for all your help!!

 

[Vettefan87]

Any type of fuel gauge. You just screw it onto the schrader valve and then check the pressure.

 

[Ted Krempa]

Have you checked the intake/air cleaner area? Maybe you have a animal in there blocking flow

 

[asby69]

Have you checked the intake/air cleaner area? Maybe you have a animal in there blocking flow

Yeah, I looked.....no squirrels or rats. LOL

I even tried it with the intake duct unhooked from the TPI, same results.

Thanks.

 

[asby69]

The regulator is at the back of the injector rail in the crossover,under the plentum. You can check the pressure on the fuel rail.The pessure should be 41-47 psi. But you need to trace the vacuum line to make sure it don't leak.

Glenn

Ok, I tested the pressure. It was about 37-38psi after just turning the ignition on, then about the same with the engine running. I let it run until it quit, the pressure didn't change after it quit?!?!!?!

Another thing I noticed, the cooling fans come on as soon as I turn the ignition on even with the first start of the day (engine cold) and stay on until the engine warms up and quits. The engine temp gauge seems to work normally. Is there a sensor that might be causing my problem?!?!?

Thanks.

Asby69

 

[G Winter]

If it is sensing the engin to be cold it would be putting extra fuel in when it is actually warm. Not sure if it would be enough to cause it to quit. I would be looking at that as part of the problem. You could also have injectors that are leaking badly. Just some ideas off the top of my head.

Glenn

 

[asby69]

Update:

I tested HEI ignition module - Good.
Replaced the coil due to cheap cost (while testing Hei).

Still same problem. I timed it, it runs exactly (almost to the second) 10 minutes then quits.

Sorry I don't have codes, it won't make it to the shop to get "coded"....

HELP!?!?!?

 

[asby69]

More info that will maybe help in diagnosis;

Right before it quits, the engine picks up in RPMs a little, then it sounds like it takes a slow, gasp for a last of breath of air (like a sucking sound) then quits.


Thanks again all.

 

[G Winter]

More info that will maybe help in diagnosis;

Right before it quits, the engine picks up in RPMs a little, then it sounds like it takes a slow, gasp for a last of breath of air (like a sucking sound) then quits.


Thanks again all.

put a vacuum gauge on it and see if the vacuum drops as it runs longer.
I am now thinking catalytic converter may be plugged. That last gasp statement is what clued me . That would also make it run richer because the regulator increases pressure with vacuum drop.

Glenn

 

[asby69]

put a vacuum gauge on it and see if the vacuum drops as it runs longer.
I am now thinking catalytic converter may be plugged. That last gasp statement is what clued me . That would also make it run richer because the regulator increases pressure with vacuum drop.

Glenn

Hmmm, I have a new exhaust system on it. New front Y, New Cat, New Rear Y, and mufflers. What are the odds of a new cat being jacked up?

Where should I hook up a vacuum gauge?

Thanks.

 

[G Winter]

Not real sure where to hook the guage. Always the chance that you got a bad one the had the inside break loose. I have seen some exhaust pipe that is double wall and the inside wall will sometimes collapse from high heat.I may be wrong on the exhaust being restricted but things sure point that way. Before this did it seem to lack for power?

Glenn

 

[asby69]

Not real sure where to hook the guage. Always the chance that you got a bad one the had the inside break loose. I have seen some exhaust pipe that is double wall and the inside wall will sometimes collapse from high heat.I may be wrong on the exhaust being restricted but things sure point that way. Before this did it seem to lack for power?

Glenn

No. It always ran strong?!?!? The only thing different that I've noticed is that the cooling fans come on as soon as I start it, even when the engine is "cold", like first thing in the morning. The temp here has been in the 20's in the mornings, I don't think the fans should come on. I know they did work correctly before this???!!?! I'm stumped....LOL

 

[G Winter]

Maybe the ECM took a crap?

Glenn

 

[Rogier]

Thanks!! Ok now, where is the fuel pressure regulator?

With these questions trouble starts...

Look on the internet for maintenance explanations. These sites are very helpful although I think your problem will be somewhat more difficult.

 

[asby69]

Update

Update:

I jumped the A & B connector on the diag connector and get codes 12 & 15.

Any suggestions?

 

[asby69]

Code 12: Diag Mode

Code 15: Coolant temperature sensor signal indicates a temperature colder than -38? F for 3 seconds.

Could the temp sensor be causing this? If so, exactly where is it located.

Thanks.