Fuel line check valve? Pressure drops after ign OFF.
 

I have a SXperformance adjustable fuel pressure regulator on fuel rail and RSI twin pump in tank. I use original fuel feed line and I have fabricated a return line. Fuel filter I got from 97-98 model that is lacking the regulator.

If I understand correctly, the one-way valve is located in the fuel feed line between pumps and filter? It's still there because I'm using the original feed line..?

Fuel pressure drops to zero after pumps go off in 10 seconds.

There could be a leak in the regulator too but the fuel pressure is static when pumps are on..

Your fuel pressure regulator could be designed to always allow some fuel flow through it (doesn't seal completely). I have had one in the past that the manufacturer said would always allow some fuel to flow. It wasn't the brand you have though.

To check you can disconnect the return line and pressurize the system. If fuel flows through the line after the pump is turned off that is where the fuel is bleeding off. You could also cap the return line and momentarily pressurize the system and see if the gauge shows the pressure dropping. Be careful if you do this, you will build pressure really quick because the fuel has nowhere to go, and when you remove the cap the fuel is still pressurized....

Hopefully easyvette chimes in...I know he experienced this same problem. One of his injectors was hanging open if I recall correctly??

Are you using 255s?

Yes.

Earlier I had GRJ420P with BAP and I had the same problem then. Of course the same regulator was there also.. Too bad I can't remember if the the pressure drop was present always with that SXperformance regulator.

I see the same scenario with my FPR, fuel pressure (measured at the fuel rail on; on top of injectors) drops after key OFF. I have an Aeromotive FPR on my rails and in the manual it states that it will not hold pressure after the fuel system is shut off.

Quoted from manual: "The enclosed fuel pressure regulator may not hold significant fuel pressure after the fuel pump stops running"

I see the fuel pressure drop little by little, I would say it takes a full minute to go to zero though.

Hope that helps.

Later,
Max

I had a similiar problem and added a check valve up front just before the rails on the feed line. Car starts on the first try and fuel pressure holds all the time.

I dont know guys... I am running the aeromotive FPR (boost refferenced) and walbro pumps. And after shut down my fuel pressure drops to 40psi and holds for a long time (hrs). Borrowed a friends aeromotive FPR identical to mine and it worked just like mine. So I am gonna go out on a limb and say it should hold fuel pressure for a while. If your pressure is bleeding off rather quickly my best guess is you have a problem and you need to address it.

I pulled my hair out tracking it down testing the lines and the FPR over and over again. Pulled the fuel pumps to make sure they were not bleeding off. I finally isolated down to a hanging injector. It was my last guess... Probably from cutting braided hoses some dust. When I figured out the problem I was at my witts end and preparing to send my injectors out to get cleaned. As a last resort before sending the injectors out I dumped a bottle Teckron fuel treatment in and 75 miles later I was once again holding fuel pressure after shutting the car off.

Just remember if you are dumping raw fuel into a cylinder after shutting down the car it will find its way into your oil and thin your oil out.

The FPR i metioned above was an Aeromotive also. I talked to them about it and they said it was not designed to hold pressure when the pump was off. I'm running a bigger Aeromotive regulator now that drops about 8lbs of pressure and then hold constent when the pump is turned off. I guess each model doesn't function the same.

I agree with easyvette. Do you have a hard time starting when hot? A leak in the fpr will back up in the vac hose I think. Check your plugs to see if any are wet. Teckron is great stuff but remember all the crap it loosens up will wind up in the filter and the injector filters as well. Hope this helps a little, Good luck with it.

95vettski, do you remember what check valve you used? Was it something off the shelf or did you have to do some custom plumbing? My fuel pipe with the inline check valve just before the fuel filter has failed, and GM has discontinued the part.