MillsMotorvation

I installed a boost referenced Aermotive reg on my LQ4 1981 TTA swap, added turbo, and intercooler. Well after giving the car a little boost, the fuel gauges go back to zero when the car is shut off. All before it would hold 40-50 for a long time, I checked for leaks, and dont see any. I have a external 340Walbro. Will the FPR send the fuel back to the tank, and cause fuel psi to drop? Car run good other wise.

Old Geezer

iTrader: (3)

2 ways for Fp to drop:
1. The check valve in the pump is not holding. [Assuming it has 1.]
2. Leaking injector[s].
Could be a 3rd. If the reg works correctly, then it should hold the fp. If the reg is leaking, then there's the 3 way back.

How is the reg plumbed?

MillsMotorvation

Got the pump run in one end of the rail, and out the other side to dead end to reg, then the return coming out the bottom of the FPR.

Old Geezer

iTrader: (3)

Shut the engine off, and immediately pinch off the return line. PSI still drop? That removes the reg from the equation.
Injectors: Shut the engine down, and pull the plugs. NE of them wet w/ fuel?

MillsMotorvation

Thanks alot, didnt think of that!!

MillsMotorvation

I pinched the line from the FPR and the fuel psi stayed up 100psi with car off, then took the pinch off, and it stayed at 40-35psi. Being its boost referenced it still should hold psi right?

Old Geezer

iTrader: (3)

@100psi, you evidently pinched the line while the engine was running!
@100psi, and it holding, is a pretty good test for the system components behind the regulator.
That hi psi against the pump may have knocked the check valve back into position. [Assuming it has 1] Holding 35-40 after release is what I'm basing the comment on.
Now, after the test, does the system hold psi after running and shutdown?

Boost reference has nothing to do with retention of fp after shut down.

Lonnies Performance

iTrader: (16)

The order of shutting car off & then pinching line is very important.

Your pump can make enough pressure to damage the regulator, a line or itself.
Do NOT pinch the return line with pump running. Only do this after shutting it off.

MillsMotorvation

Ok, I did'nt have it running, just switched it on while pinched, but wont do that again.