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quick99si quick99si is offline
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Posts: 35
Join Date: Jul 2013
Default N54 engine swap resulting in crashing HPFP (two separate pumps) - 08-07-2019, 02:38 PM

My original N54 spun a bearing so we swapped in a lower mileage engine. The new engine idles fine and runs great off boost, but backfires badly in boost at high RPM. We found some shredded belt material around the chain, but this was cleaned up thoroughly. My car sat for about a month and now it looks like I have fueling issues.

In each log below, the HPFP climbs to 13 (1950psi), crashes to 2 (300psi), and recovers to 10 (1500psi). By then, injectors have shut off and DME goes into limp mode.

1. https://***********/u/quick99si/dann...0&mark=7-20-25
2. https://***********/u/quick99si/dann...og=0&data=1-10

Thinks I've tried:
- Check for vacuum leaks
- Verify O2 sensor positioning
- Remove JB4
- Reflash DME
- Replace LPFP sensor with a used one
- Replace HPFP with my original pump (working fine)
- Log LPFP in INPA/JB4

No mods except JB4. 110k miles. Not sure if it's worth looking at plugs/coils/injectors since there are no misfire codes.

Is this a clear sign of a failed HPFP or is still dubious at this point?

VRSF DP | VRSF 7" FMIC | ER CP | HKS BOV | BMS DCI | BMS OCC | JB4 G5 | CM10 | Alpina B3 Trans Flash
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