I have been having starting and fuel pressure problems ever since I installed an aftermarket Walbro fuel pump. It turns out that the plastic fuel line that was provided in the kit when I bought it was leaking inside the tank. It was the line that runs from the fuel pump the the hard metal fuel lines at the sending unit. So I replaced it with a piece of high-pressure rubber fuel line. Starting problem fixed, it fires right up now without having to prime the pump 2 or 3 times. My only concern is that when I simply prime the pump, or when I shut the motor off, the fuel pressure drops from about 48psi where I have it set at, to about 30psi, and then it drops slowly from there to 0psi within a minute or so. Can anyone tell me if this is normal or should it stay at 48psi before I put it all back together. Thanks,

 

I think you will get better results on this post by putting it in "General F-Body Tech & info". I'll move it there for you.

 

The pressure will eventually bleed off but it shouldn't reach 0 in 60 seconds. I'm not as up to par on aftermarket pumps though so it may be normal for that pump, I just know its not normal for factory pumps. Did you remember to put the clamps on the hose at the pump because it could be bleeding off there. Otherwise I dont know but that definatley dosen't sound right.

 

Dirt can cause the check valve in the pump to hang open. May just need to be cleaned.

 

Quote:

Originally Posted by Cmr0z28
I did not use a sock on the pump. There was a screen on it, and the sock they gave me wouldn't fit.


The diagnostic procedure laid out in the GM factory service manual should be used to properly diagnose this type of problem.

The sock we provide fits on the bottom of the bucket not the pump.
The pump fits inside the bucket.
http://www.racetronix.com/product/RX...LT1-FPKG-2.jpg
If the proper sock is not used debris can get into the pump and lodge itself on the checkvalve seat. The white 30 micron sock provided must be used. The bucket etc. should be cleaned and caution should be taken to avoid even the smallest piece of dirt from entering the pump during the installation process.
__________________
Racetronix
Fuel Systems:
F-LT1, F99-02, F-98, Delphi & Siemens Injectors, 32#, 37#, 42#, 60#

 

I remembered to put hose clamps on both sides of the fuel line and I reused the stock sock that fits on the bottom of the bucket.

 

Bad fuel pressure regulator can cause it not to hold pressure as well. If there is a rubber line on the return line, then energize the pump and then cut it off, before the pressure drops you can pinch the return line off with a pair of vice grips and it thats the cause, the pressure will stop dropping when its pinched off.
If pressure continues to drop, could be a leaky injector or the check valve.

 

Could somebody with a fuel pressure guage do me a favor and try this on your car and see what happens: like I said, energize the pump to prime the system and then watch the guage to see if the pressure stays steady or if it slowly runs down to zero withing a minute or so.

 

The pressure should be at about 40# with the pump energized. As soon as you shut it off, it usually will drop to about 25-30# within a minute or so, and then slower drop from there down to 0 in about 10-15 minutes is the norm. Just had a gauge on my LT4 motor in my truck a few weeks ago to check the accuracy of my electronic gauge.

 

Thanks, now I know it's bleeding off somewhere because I'm down to 0psi within a minute or so.