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      10-14-2021, 04:56 PM   #42
thejeremyman9
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Drives: 2015 BMW 335i
Join Date: May 2019
Location: Cali

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Quote:
Originally Posted by LA1Z24 View Post
I have a theory that BM3 is overdriving the HPFP regulator driver in the DME, and rather than smoking the circuit, the ECM goes into a safety mode by cutting down the command to the HPFP. Unfortunately the location of the HPFP makes it difficult to put an amp clamp on the wires to see if the actual command signal falls back, while the command in the datalog is still calling for 2400psi.
If i understand what you are saying correctly, his problem is the opposite, because the car is actually delivering too much fuel. So it's not just that he has a fuel pressure drop when he shouldnt, but it looks like the fuel pressure drop is "real" in the sense that the pressure drops because the pump can't keep up with the actual amount of fuel supplied. The thing is we don't know why the tune is telling it to supply that much fuel (except for strange fuel trims)

It seems like you are saying the DME might be telling the HPFP to supply less even if the log says the target is still say 2400. But if that were true in his case, he wouldnt have the fuel trim issue and the super rich AFR that corresponds with the pressure drop.
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