I have been having some problems with my car not starting starting up right and taking forever to start also it has been dieing on me sometimes and has a stumble once it gets warmed up. We tested my fuel pressure and it is about 36 psi at idle. BUT when we turn the car off the pressure dies down instantly to 0. I was told that the pressure should stay for several minutes after you turn it off but its not. When the car is turned off the needle just drops steadily and its down to 0 in about 5 seconds. I am guessing my fuel pump is bad and its the cause of my hard starting and stumbling. Any info is appreciated, Thanks, Dustin.

 

The fuel pump has a check valve though, if you've got good pressure...that seems a bit low though, it may not be your problem... It could be electrical also..ie plugs, wires etc...

J

 

Sounds like the pump to me, but it may be the regulator or 1 or more injectors as well.
We had similiar problems on my friends 350TPI motor and it was a few things, Pump had a bad check valve, 2 injectors were leaking, and the cold start injector was leaking.
Put on a new pump, changed injectors and closed off the cold start injector and all was good.

On the TPI cars, there are rubber fuel lines near the rail and we were able to clamp them down to test the system. An LT1 car with the plastic lines makes it harder to test.
Start with the easy things first.

 

if it drops "that" fast it's a real good chance it;s the pump. is it hard to start after it's been sitting or just anytime you try to restart? when it does start is it really rough? in not the I would almost rule out an injector

 

Small write-up about checking pressure.

 

When the engine first starts up you have to give it some gas usually to keep it running, sometimes it will start fine but most of the time it requires a little assistance from the gas pedal to stay running. After a few seconds you can let off the gas and it will idle on its own. The car seems to be easier to start when its warmed up or has been started recently, like say within half an hour. When the key is turned and the fuel pump turns i think its only hitting like maybe 20 psi before i start it up, i am not sure i just remember glancing at it. But when the car runs its about 35 psi and instantly looses pressure the second the car is turned off. Hopefully this is a little more info to work with. Dustin

 

Are you running the stock fuel pressure regulator?

 

Check your coolant temp psensor on a scanner. It needs to accurately tell the PCM the coolant temperature, so it can set the cold start A/F enrichment, and the cold idle speed.

Check the IAC counts on a scanner. Do the IAC counts respond correctly to the "near stall" condition?

And obviously, use Shoebox's link.

 

Check your coolant temp psensor on a scanner. It needs to accurately tell the PCM the coolant temperature, so it can set the cold start A/F enrichment, and the cold idle speed.

Check the IAC counts on a scanner. Do the IAC counts respond correctly to the "near stall" condition?

And obviously, use Shoebox's link.

And that's a good point on whether you have the stock FPR. Some aftermarket AFPR's do not hold the pressure, to relieve the pressure on the injectors when the engine is shut down. I know my Weldon outboard AFPR does not hold the pressure, and isn't supposed to.

 

Well, the aeromotive regulator I had on my TA was junk. It ended up leaking around the diaphram and into the intake manifold which caused the car to be hard to start and to run really rich. Easiest way to tell is to pull the TB off the intake and shine a light inside. If it's damp, then that's most likely your problem.

 

Ok here is an update. I got out there this morning with the pressure guage and hooked it up. When i turn the key to the on position the fuel pump starts to prime, pressure is only hitting about 4psi while priming but when the fuel pump stops it goes down to 0 almost instantly. Also, the pressure was 36 psi at idle with the car running with the vaccum line connected, after disconnecting the vaccum line pressure went up to 44psi. I turned the car off and by the time i had gotten out of the car and looked at the gauge again it was back down to 0 already. I should also note that the car was loping really bad and even died on me once while this was going on. Keep the replies going, I am determined to figure this out, thanks, Dustin.

 

just follow shoebox's website and you will figure it out.
-b

 

The coolant sensor as well as the sending unit are both good. Are the tests that i have performed still not enough to diagnose a specific problem??

 

When your driving, does it seem like you are losing power at WOT? As if the car is flat and running on only 6 cylinders.