just took the car out with the fuel pressue guage hooked up. car primed fine. started fine. ran fine until...........about 150 degrees then as i was accelerating i felt the car start to die. there was NO change in fuel pressure. after i let the car slow down i pushed in on the gas, with the fuel pressure reading about 40psi and the car started to gain speed until about 35mph then the car started to stall (for lack of a better term) and as the car stalled and began to misfire and at that point i noted a slight drop in fuel pressure but it was after the car started to misfire and it was about 4-5 psi.

suggestion?

 

If you are POSITIVE it's not the injectors nor AFPR, and you have a NEW fuel filter, then chances are it's the fuel pump / sending unit or possible faulty wiring to the fuel pump / sending unit.

 

I thought you were on the right track initially when you removed the cat, which seemed to help some, right? So this might seem like a longshot and not related to the fuel system like everyone's analyzing, but what about the opposite end of that--the air intake?

I've had a clogged cat, which acted just like yours did, AND I've had a malfunctioning MAF, which acted exactly the same way, too. And since all your fuel-related components are checking out ok, but the engine is apparently starving for something, what about air and/or throttle?

 

thanks guys.....

LA.... i have a speed denisty system and a holley 52mm throttle body. i haven't seen any obstructions, so i kinda think it's ok on that end. appreciate the suggestion though.

badz.....

the car still is doing the same thing with all new injectors and AFPR etc. so maybe it's time to look elsewhere. that is why i wanted to take it out with the guage hooked up.

would i notice a change in the fuel pressure if it was shorting? will i see a variation in the voltage at idle if it only does this above a certain rpm?

 

Time to change the fuel pump / sending unit. Also inspect ALL wiring going to it for damage.

 

Alright people, i just took the time to read this whole thing to try and help figure out what is wrong, I see that the fuel pump has been changed (well what hasn't been changed). Alright, you said that you changed the injectors, now let me ask you this, are u running the stock TPI set up or an after market TPI set up? That is actually going to be the real question here.
The reason for me asking is because, with the motor under stress parts are going to move and actually make burrs on other parts from the friction, my stock TPI intake on my 87 IROC started to give me problems when it had 70,000 miles on it. My fuel pressure would slowly drop when the key was turned, it took me days and even weeks to find out what this problem was, it turned out to be the stupidest thing that has ever occured to anyone(had to be me). The number 7 injector decided to make a burr where the fuel injector meets the intake and started to ground the injector on that burr, what started to happen is that the fuel pressure would be fine and then slowly go down, but while the car was being driven it was even worse because of the vibration and made it leak into the cylinder even more then it already was. To be honest with you it might be a shot in the dark, but the stupidest things are usually the ones that hit people by surprise, so what i'm saying is to take the injectors out and check where they meet the base and see if there is anything that shouldn't be there, take your finger and feel around just to make sure. But like i said this happened to me and when my friend put on the edelbrock intake it did it to him right off the bat, but i hope that you find out what it is so you can enjoy your car instead of being p----ed off at it, and please don't go to carb, just stupid talk, take it easy man and best of luck!!!!!!!!

 

as you read.....the fuel pump and pulsator have been replaced with ac delco parts and it continues to do the same thing. the intake had about 10k as did the injectors without a problem.

when i replaced the injectors i cleaned out the areas and did not notice anything unusual.

the tpi is stock but it is an aftermarket chip because it was a 305 now it is a 350.

the guy at holley claims the pressure regulator is desigened to drop pressue unless you start the car. since it did the same thing with the 2 holleys but not the jet AFPR i now believe him.

also the car maintains perfect pressure while at idle or even when you drive. that is until you get to the majic 150 degrees.
the ONLY time the fuel pressure drops is while you accelerate while the car is running.

 

ok, problem solved.

finally got tired of all the guess work and took it to the dealer.

after a day and a half i got the answer. first there were NO error codes comming out of the computer.

and the answer is............




well acturally they found 3 things

1. ignition coil (most likely the real culprit here)
2. accel coil (this was the second one and it was nearly brand new, first one died in a day)
3. the distrubtor bearing was shot. (person who installed engine repeatedly assured me 'it was fine'. don't think i'll use him again)

anyway, thanks for all the input.

as my hero forrest gump says "and that's all i have to say about that"

 

[QUOTE]Originally posted by slohand
ok, problem solved.

finally got tired of all the guess work and took it to the dealer.

after a day and a half i got the answer. first there were NO error codes comming out of the computer.



Hey slohand, are you still getting the pressure drop after priming the pump? I have the same problem but when I adjust the regulator(homemade) the pressure will shoot up to around 70 psi and slowly go down to around 40.

 

oh ya.

as i stated before they are telling me the holley is designed to release pressure. go figure. when the pump primes it goes up to about 38 and then starts to drop back down. BOTH of the holleys i tried did the exact same thing. that is why i called holley. the car starts and runs fine, just ask the poor shmuck in the sho who thought he would give it a try.

 

Hey slohand did the shop explain to you how the coil affected your fuel pressure? I am curious how the two are linked.

 

Hello OMCRIDER,

The bad coil wasn't the cause of his fuel pressure drop and had no influence on it. His fuel pressure drop was caused by the Holley Adjustable Fuel Pressure Regulator he had installed. This regulator according to the folks at Holley, is designed to release the fuel pressure after priming.

 

Thanks Trickster I read that entire post twice, and I caught that which is good to know becasue I just bought one. I thought he was saying he would see his pressure drop after the stumbling started. Anyway reason for my curiousity is I have good fuel pressure until the car is ran a short distance then I am dropping about 10psi. Reads strong when fired up for a short period, holds pressure with ignition on motor off setting. Just trying to determine if its leaky injectors or fuel pump getting weak. I saw and noted your comments above about the checking leaky injectors by pulling fuel rail, since I have an intake and AFPR to put on anyway I'll think I will do that. If there not leaking then its probably the pump.

 

well how the heck are you TRIX? hope the hand is doing well.

hez right, coil unrelated to the fuel pressure. pressure is and was fine except for the bleed off at startup.

now, some info you may find helpful. with the holley i notice you have to turn the key and wait for it to prime. also when it's cold i have to try to crank it 2 times after the prime before she hits. i believe this is related to the 'bleed off' of the holley AFPR. at least that is what i have chalked it up to.

happy motoring!!

don't forget to wave bye to the mushtangs!!

 

Well Hello Slohand,

Fiqured you'd be popping in tonight. The hand is doing much better now and the wife has given me her honey-do list that she has been compiling for the last month and a half. Still no word from the folks out at the old air base yet and nothing from the other places I've visited. Will get an e-mail off to you later tonight.