So I have a series III 3800sc running a 2003 GTP ECM and the EP381 fuel pump. I used returnless setup (Ryan's) with a Series II FPR. I get 49psi but it drops quickly to the 20s (in like 10 seconds). So I guess I may have a problem with the junkyard FPR as there is no leak. I need to troubleshoot that. But the question is, what fuel pressure should I really need to run per the info below? 49psi or 56+psi? Or it doesn't matters because the ECM programming (tuned by Ryan) is supposed to take care of that? Thanks.

" If you have a no-start condition because there’s no fuel, the first check would be fuel pressure. On a Series II 3800 engine, fuel pressure should be 48 to 55 psi with the key on and engine off. GM does not provide a fuel volume test spec but, as a rule, a good pump should deliver about a quart of fuel in 30 seconds.

On a Series III 3800 engine in a Buick Lucerne, the returnless EFI system has the fuel pressure regulator mounted in the fuel tank with the pump instead of on the fuel rail. There is no fuel return line from the engine back to the tank. The fuel pressure on these engines should be 56 to 62 psi with the key on and engine off."

Source: http://www.underhoodservice...3800_v6_engines.aspx

48 PSI without vaccuum and 42 with...PSI should go up when giving it throttle...

Will the FPR for the 3800 work the same as the stock Fiero o ne? You know that if you put the ignition on the fuel pressure will rise to 45psi and then will stay there for a while. Mine goes to 49psi but then pressure drops quickly (like in 5-10s) to 29psi and keeps dropping. I haven't tried to start the engine yet (other stuff pending). Tks

quote Originally posted by Alex4mula: Will the FPR for the 3800 work the same as the stock Fiero o ne? You know that if you put the ignition on the fuel pressure will rise to 45psi and then will stay there for a while. Mine goes to 49psi but then pressure drops quickly (like in 5-10s) to 29psi and keeps dropping. I haven't tried to start the engine yet (other stuff pending). Tks

Am I correct in assuming that when the pressure is dropping, the pump is off? As in, you turned the key to RUN, and then the pump ran for a few seconds, then shut off?

If so, it's probably a flaky check valve. The valve doesn't have much function though, besides keeping the fuel system primed for an instant turn-key start.

If your pressure drops that fast, look in these places: Fuel pressure regulator, check valve built into the fuel pump (doubtful if the pump is new ), fuel pump hose or pulsator inside the tank. A leaky injector could cause it too, but then you would have a bad misfire on start-up due to a flooded cylinder.

sounds like your fuel pump is turning off..

quote Originally posted by pmbrunelle: Am I correct in assuming that when the pressure is dropping, the pump is off? As in, you turned the key to RUN, and then the pump ran for a few seconds, then shut off? ..

Correct. I have no pulsator. Pump is new. I just pinched the return line and it holds pressure so pump should be fine. I changed to another FPR from a 98 3800 non SC. Looks very similar but internally is a little bit different. The other one was from a 99 SC engine. With this one pressure goes to 55psi w which I like better. Weird thing is that same thing happens but is not always. Sometimes it stays in the 40s for over one minute but sometimes it drops quicker. Not sure yet but maybe I should just buy a new one.