Fuel rail pressure not remaining constant

[Nchristopherson]

When I prime the car, it jumps to around 44 PSI max which seems low, but it also falls drastically once the fuel pump has turned off. Bad fuel pump check valve? Will this require replacing the fuel pump? It also stays around 39-44 PSI while running.

 

[Fivefingerdeathpunch]

Not sure what year you have but a bad regulator on the fuel rail and cause the drop in pressure after you prime it.

 

[Scottydoggs]

sounds normal to me. as long as the cars running ok. iirc you want to see over 33 psi running

 

[BillBoost37]

I have seen the check valve in the pump or the pressure regulator cause this issue. Typically I discount the drop in pressure as long as the car starts on the first try. Then read the pressure running, as long as you aren't dropping in pressure at the higher rpm it should be acceptable.

 

[Nchristopherson]

Hm ok. It is a 2002 GT. I was using this guide as a reference for testing it: http://www.fastfieros.com/tech/fuel_pressure_L67.htm

During a cold start, it takes probably 1-2 seconds of cranking to start. After that, it seems to start up fine. Pressure remains 39-43 while driving. No issues that I can see for driving, except that I get KR super easily and can get up to 10*. But I figure that probably isn't related to this.

The regulator does look a bit wet, but doesn't feel wet or smell like gasoline. No fuel in the vacuum port either. I am just concerned because the guide on fastfeiros says 45-55 PSI and that it shouldn't drop more than 5 psi in 10 minutes, but it drops 5 psi in probably 15-30 seconds.

A side note, my fuel trims are +16.4 at idle, which should point to a vac leak I would assume, but I have double checked any gasket I can think of for any stuttering. Idles super smooth, no hesitations.

 

[SnowTh1ef]

if fuel trims are +16.4, you have a vacuum leak, and need to find it. lol