Hello, my 01 trans am fuel pressure falls rapidly after initial priming before engine cranking. It goes to 60 psi without trouble during priming, and then once the fuel pump cuts off it falls off quickly to zero. Does anyone have ideas, maybe even decisive ones, about what is causing this? The engine runs great, but because of that i must start it while the pump is still priming. Otherwise the engine may start and stall after a second or have trouble starting. Thanks a million!

 

pump could be leaking down
If an injector was leaking that bad you might see smoke at start up and probably has a misfire

 

cool, thanks, so does that mean replacing the fuel pump is the best option? Or is there a replaceable check valve causing that?

 

additionally, it is definitely not an injector because i took them out and had them cleaned and tested within 500 miles ago. They all tested ok and very close

 

this was a restoration job after sitting a long time. This problem was ocurring before taking out the injectors too.

 

After putting in a new fpr and pump was still having issues. Turns out the clamps on the intank fuel lines were leaking. I didn't do the initial work but ended up hooking up the pump out of the tank and put it in a glass bowel to see what was leaking.

 

very helpful, thank you

 

I know this is an old thread now but wanted to come back and post the outcome. I replaced my fuel pump, and that did the trick. It holds the fuel
pressure after priming now, which makes the engine much easier to start. My old fuel pump was leaking internally. I did not examine it to see how. Additionally on a dyno with an external o2 sniffer in the exhaust while i had the old fuel pump on it in the higher rpm range and full throttle it would run lean. I suspect this was because of the internal leak making it not able to keep up with fuel demand. I'm taking it back to that dyno soon to see if that problem is corrected as well. But i can definitely tell already the engine runs better. It was running good before, but now it is just much cleaner and smoother. Anyhow i've been working on this restoration job in my spare time for a year now--every now and then sort of. The work is really starting to pay off, and my trans am is really coming to life! And this forum has been a ton of help. I really appreciate it. I'm amazed at how useful this forum is with the knowledgeable people who post regularly. People with modern muscle cars on the road i think feel threatened by my trans am and always react when they see it haha They either floor it or rev their engine. Or maybe they are just complimenting it. I don't know, but i think the old model american muscles are so much better than the new ones. People used to complain that gen 4 f bodies were too heavy at 3,200 pounds (I weighed mine at a cat scale), but now chargers are 5,000 pounds! That's a waste of power!