Fuel Pressure/Pump Woes

[Deserion]

I'll try to keep this as factual as I can to make potential diagnosis easier.

2004 Boxster 2.7L manual, 90xxx miles.

3/30 - Last drove car, no issues. Parked with 1/4 tank (generally refuel a Shell).

4/1 - Attempted to start car, cranks but did not fire. Tested with Durametric, crank signal reads approximate 162 RPMs during cranking (also displays on tach).

4/6 - Replaced fuel pump with OE part (ordered from Porsche dealer) after determining car has no fuel pressure and pump failed 12v application. Once new pump is installed, car immediately starts and drives normally. Start/stop car multiple times without issue. No debris in tank, no kinked lines. All connectors clicked/tightened correctly.

4/7 - Attempted to start car, cranks but did not fire. Checked fuses, no fault. No fault codes read with Durametric. Changed DME and injector relays, no change.

4/10 - Replaced ignition switch. No change.

4/12 - Replaced fuel pump with another new OE part (from Porsche dealer). Again, car starts up and drives normally without issue. Cycle ignition and works perfectly. Fuel pump is audible upon power-up every few ignition cycles (if cycled rapidly), comes on momentarily then shuts off (not stuck running). No debris in tank, no kinked lines. All connectors clicked/tightened correctly.

4/13 - Attempted to start car, cranks but did not fire. Fuel pump not audible as was roughly 12 hours prior. Car now has a little less than 1/2 tank of fuel (new pump was submerged completely in tank when replaced).

4/15 - Replaced fuel pump relay, no change.

Now, the original fuel pump was disassembled and found to be seized. The first replacement was briefly bench tested and did not turn on (I did not perform the test so I cannot confirm this fully). When ignition on, power is present at sending unit/fuel pump harness plug (will determine exact voltage and amperage today).

Now, is there ANY idea as to why the car will run with a new fuel pump, only to not start 12 hours after the last shutdown? I'm out of ideas on how to diagnose this. Part of me thinks there could be a grounding issue with the pump, also think that it could be a bad DME or crank sensor perhaps (though the car runs immaculately when a new pump is installed).

I haven't been able to find any other real answers on how to solve this, and I'm sure I can't keep having fuel pumps warrantied. Anyone at Pelican HQ with an idea (Wayne)?

Thanks in advance for your assistance. I'm hoping to have my Boxster back on the road soon!

[dghii]

Just curious and not implying that this is a problem but have you replaced your fuel filter during your repairs?

[Deserion]

Originally Posted by dghii

Just curious and not implying that this is a problem but have you replaced your fuel filter during your repairs?

Standalone fuel filters are only on 1997-2001 Boxsters. The filters are not replaceable on 2002-2004 models.

[Deserion]

4/17 - Tested second replacement fuel pump with direct 12v power. Pump buzzes as if motor stuck, does not push fuel out of the tank. With pump relay bypassed, power socket at tank gets continuous power, but with relay in place momentary powerup upon turning the key intermittent (as seems to be normal).

Right now the plan is to get (another) fuel pump, and also change the sending unit as well. I'm wondering what the failure rate is of the fuel pressure sensor (on top of tank and connected into EVAP system).

[Deserion]

Problem solved! Updating this so anyone else searching can see my resolution.

I returned the second faulty fuel pump, and ordered a used pump and sending unit from DC Auto. Along with those new (used) parts, a fresh fuel pump relay, and fresh fuel, the car performs. Period.

The gas I pumped out of the tank smelled old and not nearly as strong as gasoline is supposed to smell. Even after getting it on my hands, the smell largely disappeared - kind of odd. So with a dry tank, I installed the (very lightly) used pump, then the used sending unit. All locked in, I dumped in 5 gallons of fresh 93 octane (which DID smell strong). Turned the car on, nothing. Forgot to put the new pump relay in (old one was installed), so I swapped that out. Cranked, fired, booyah.

I waited about 2.5 hours and tried again. Started. On my way to work this morning (about 11 hours after the fix was completed), the car fired right up. Refilled the tank with fresh gas, then went to work. Started right back up after sitting.

I'm so, so happy to be driving my Boxster again. I sorely missed having it on the road in the last three (almost four) weeks.