I am having a fuel pump problem - no pressure. Hopefully you can help me string together a set of tests that will ensure I don’t need to pull the fuel tank until it is CERTAIN something wrong with it vs. an issue with the relay, filter, regulator, etc.
I don’t have a fuel level gauge, but I do have a fuel pressure gauge on the logger. On track, during a very conservative warm-up lap, the pressure dropped from 43.9psi to 8.5. The car eventually died and I parked in the grass. I thought I simply ran out of gas, but adding 7 gallons did not change the situation. Let me give you the technical details:
- The inertia switch was never tripped (but I tried to reset it anyway!)
- The fuel pump spins up each time I put the ignition into start. It sounds normal. Presently, the pressure increases from 9 to 11psi, not the customary 30+ psi.
- I do get some internal combustion - the engine does turn over, but it doesn’t sustain - it basically sounds like a healthy engine getting only 9psi through the fuel system.
- On either side of the fuel rail, I clamped off the input hose, the output hose, and then both hoses together to see if I could affect any change (tested according to Service Manual pages 20 and 21 in section EMN) - the three tests did not change pressure beyond fractions of a PSI.
- I unplugged the vacuum host from the regulator, change in PSI was less than 1.
- I have not received a new fuel filter yet, and I didn’t see a simple way to remove it from the fuel circuit to test without it. - Could a fuel filter get so clogged as to clamp off 20+ psi? (sounds doubtful)
- Even though the fuel pump spins up and sounds OK - it’s a 3 stage unit - is it possible to sound ok but still be broken? Can one of the 3 stages be broken while the others function normally (sounds doubtful)?
- Since fuel pump spins up at start time, does that mean the fuel pump relay is ok? Don’t relays “operate or they don’t”?
- If I remove the fuel pump’s access cover, can I perform an - albeit dangerous - test with the two hoses right at the pump? What if I hooked input and output together via a clear plastic hose, and unhooked the starter relay? Would that be like “Crossing the streams”? 40 days and nights of Locusts? Dogs and cats living together? Is it possible to observe 10psi vs. 40psi in a clear plastic hose?
Reading through similar issues documented on this website over the past 4 years, I didn’t see anything that was “similar enough” to my problem - the only individual who actually pulled out the gas tank found the fuel pump to be ok. I want to learn from that mistake. Thanks a lot for your help in advance.