Will the Fuel return line check valve cause KOER fuel issues?

[40BelowSummer]

Will the fuel return line check valve cause any issues with KOER?
After the fuel pump primes I immediately lose all fuel pressure in the fuel rail. No external leaks and brand new fuel pressure regulator. 255lph pump primes everytime - as indicated by the sound and FP gauge. I can hear the fuel going back into the tank after the pump is primed a few times.
Is there a check valve built into the fuel pump (255lph)? If there is will it cause an immediate loss of fuel at the fuel rails?

I lose all fuel pressure after fuel pump primes, car starts and runs but cuts out at high rpm's and runs super lean now.

34psi @ idle, about 29 or so @ WOT (idle), and 39psi @ idle w/ fpr vavuum disconnected


Thanks!

 

[40BelowSummer]

bump my dog chewed up my service manual

 

[Rockledge]

Ground the fuel pump pin on the EEC Test Connector under the hood and turn the key on. The pump should run.

Measure the pressure after the pump runs about 30 seconds or so and ensure that it is within specs. Next check for pressure leakdown. Fuel pressure should remain within 5 psi of specs for at least 1 minute after the pump stops running.

An immediate loss of pressure (too much leakdown) could be related to a couple of things:

1) a ruptured fuel pressure regulator diaphram. You said your FPR is new, so...

2) a bad check valve. The check valve is part of the pump assembly in the tank.

3) a leak somewhere else in the fuel system, such as an injector.

 

[40BelowSummer]

Whats weird is when I ground the fuel pump continuously it will not go over 20psi it is pretty much immediately going back into the fuel tank. It seems like I get more fuel pressure by turning the key on versus grounding the fuel pump which doesnt make sense.

I have a new SHOnut FPR, the car does run too. The fuel system will NOT hold pressure under KOEO but it will during KOER.

I dont think a leaking injector will leak that much fuel that fast. I can prime the pump about 50 times in a row and I will have 0psi, but the car will start after a few seconds of cranking.

So the 255lph pump DOES have a check valve that could be bad, but yet the pump will still work? (prime and run)

 

[Rockledge]

The check valve can be bad and yet the pump can still pump, yes.

 

[AREA 91]

I just replaced a fuel pump last week because of this very same problem. Sometimes it would hold pressure at the rail, and other times it would fall off right away. A new fuel pump took care of the problem. I believe it was a sticky check ball.

 

[40BelowSummer]

Okay so I put the new fuel pump in (255lph HP) and the rail still will NOT hold fuel pressure at KOEO. Even when I prime it 10 times the fuel pressure immediately bleeds off to zero. Immediately.

NEW fuel pump, NEW FPR, no external leaks. Any ideas?

 

[Rockledge]

Did you replace just the pump, or the whole assembly?

 

[40BelowSummer]

Just the pump

 

[Rockledge]

I believe the check valve is in the assembly, not the pump itself.

Maybe one of the other members can confirm this.