So I have been trying to figure it out for some time, when I cycle the key the car builds fuel pressure perfectly but in a matter of seconds it bleeds down. My fuel system mods are as follows:

Walbro Fuel Pump
ID 1000 Injectors (I checked using a boroscope and they are not leaking)
Inline Fuel Rail
AEM Regulator
-6AN Supply Line

I have also tried clamping the return line and that does not effect it. The only thing I can figure out is that the Walbro or something with the new fuel line or rail is allowing the fuel to back flow as soon as the pump stops cycling.

Anyone had the same issues?

 

Check valve in the Walbro may be bad...from my experience they don't work quite as well as the stock ones.

This shouldn't create any problems for you other than a few extra cranks when starting if the car sits with the key on for a bit.

 

That in part is what I am trying to solve. The car must be started before the pump stops priming, and it does take 4-5 rotations to get it to fire.

I was thinking that I might install a check valve in the line but they are around $75 shipped!!! It would probably be better in the long run to put in an inline pump or a new pump all together.

http://www.summitracing.com/parts/AEI-1510...arts/AEI-15106/

 

It's the AEM FPR. I had the same issue but thats just how it is. Even my new Full Blown twin Walbro setup does the same thing with the Fuel Lab FPR. It doesnt hurt anything and I believe is normal. If you put the stock FPR back on, it will hold pressure. It's just the design of the aftermarket FPR's but again, wont hurt anything.

 

Same thing here . I run this setup on my gsr and it bleeds down instantly after the fuel pump stops . I have had no troubles from this of any kind .

 

This was my first guess also, to test I pinched off the return line and there was no change. I am 75% sure that thi is not the issue though I have no tried to reinstall the factory regulator to test.

 

I have an AEM FPR also. I run about 50 psi fuel pressure at idle. After a day not running it still has 25 psi showing on the fuel pressure gage.

 

Holding pressure that long is rare but I have seen factory vehicles hold pressure for a very long time. I am pretty sure that this is attributed to the pump.

 

I also have aftermarket injectors and a Walbro 255 fuel pump. So the fuel system is mostly non-OEM.

 

i bet its leaking out of the short piece of hose between the pump and the fuel pump hanger