Ok I'll try and make this short. 1988 IROC, lower miles, runs great, ran the 1/4 in 14.82 (2.77 Rear end) with a 2.25 60ft. Seems like a healthy motor.

Problem: After you shut it off, it does not like to start after 15 Minutes of sitting. Takes a few times to start it, then chuggs for 10 seconds, and resumes normal idle. Even if you start it the next morning, it starts the same. BUT if I let the car sit for a few days, it fires RIGHT UP! It takes only 1 crank and it fires, no chugging or anything.

So I got a fuel pressure gage. I could only get it to fit snug on the shradder valve, I could not tighten it very much. I was afraid it was going to squirt when I primed the pump, but it didnt.

The car is in storage, and has been sitting about a month. I knew for sure the car would fire up no problem. I prime the pump, and the gage read 15 Psi. I start the car, and it fires up beautifully. At a cold idle the gage read 36 psi. The car was now fully warmed up and still read a soild 36 psi.

Heres where I am starting to worry, I am reving the motor and the pressure would go up 1 psi, thats it. It would jump to 37 when reved, then shoot down to like 34, then go back up to the normal 36 at idle. I reved it to 4500 rpm, and it would not go past 37 psi.

Heres another thing I find very wierd. I am at 36 psi at idle, I turn the car off, and the pressure jumps to 43 Psi!!!! Why?

Anyway, I then monitored the fuel pressure and heres what I got:




After the 30 minutes, I started it, and sure enough, it started like crap. At the 30 minute mark (19 psi) I primed the fuel pump, and the gage DID NOT move. I then bleed the fuel so the gage read 0 psi. I primed again, and it SLOWLY went up to 15 psi, starting crappy again, then resuming a 36 psi at idle.


I am stumped here guys! Any help would be greatly appreciated!

 

Looks and sounds completely normal, for a car that has one or more leaky injectors, and everything else working right.

Send them to Rich at www.cruzinperformance.com and get him to work his magic on them. You won't recognize your car.

 

You think its injectors?


What about the fuel pump? Only 15 psi primed? And almost no fuel pressure increase when reving it to 4500 rpm?



Thanks for the reply! :hail:

 

Hey, got a few more questions


Was I suppose to be testing with the vacum line off? It was still attached.


Also, the car does start WAY better after sitting when I apply 30-50% throttle. And I just read this usually means injectors



Thx for the help though, I appreciate it guys!

 

Your fuel pressure drop seems to indicate leakage (probably injectors), but the low pressure at restart may be a different problem. Have you tested fuel pump voltage when teh system primes? I'm thinking you may have a relay/contct problem.

 

I have not done that. How would I do that? When the fuel pump primes it sounds nice and healthy

 

Yes your supposed to remove the vacume line when you test the pressure. Your readings sound normal. When you turn the key on the ECM turns your fuel pump on for approx 3 seconds and then shuts it off if it does not receive a cranking signal. So when the key is on but the engine is not running it starts to return the fuel to the tank relieving fuel pressure. your regulator could be the problem as well.

Check your fuel relay. For it not starting after it is warmed up try advancing your timing a bit. I did this and as soon as I go to crank it fires up. Also, if you don't already have a adjustable fuel pressure relay you might want to get one. Makes a big dfference by adjusting the fuel to about 42 psi.