Quote:
Originally Posted by jbraslins
Just curious, why do you say that?
From what I understood, they hooked up the car to BMW diagnostics tool, it showed an event in DME for low fuel pressure. They followed official diagnostics steps for troubleshooting that, which lead them to replacing fuel pump per BMWs diagnostics steps for that component.
Not sure I see how you get from above to "lets just start replacing things". Please explain  |
Please understand that BMW's official diagnostic procedure involves minimizing work and replacing parts. It is not a bad procedure by any means, it is just simplified and less diagnostic. It also looks at codes as indicators of bad parts, rather than an assessment of the symptoms around that code.
According to what I read from you, the fuel rail was measuring below an acceptable level of fuel pressure. Your symptoms are more pronounced lag. And even though the fuel rail's pressure is below an acceptable level, it hasn't triggered an actual detectable event. The only thing you've seen is a DCT malfunction that, for whatever reasons, didn't even store a code.
Now maybe I don't know the whole story here. But...
1. What diagnostic was done on the fuel pressure before replacing a HPFP? Did they test the pressure coming out of the fuel pump? Did they test pressure at the fuel pressure regulator?
2. Was your fuel pressure code, which by the way did not trigger any actual warning in the car but just registered as possibly a one-time event, confirmed as continually experienced? Did anyone do a real-time data log of fuel pressures as the car was driven down the road before and after the fuel pump replacement?
You've got a symptom that is consistent with a poorly functioning fuel pump in the N54/N55 debacle, and a single stored code which never triggered an actual check engine light or similar, and they went ahead and replaced a part.
I'm just saying....there needs to be actual diagnosis done here. Maybe that will be the next step.