Quote:
Originally Posted by Absorber
This is my understanding of why Eric@AMS and CP-E suspect the issue might be related to the low pressure sensor. Please tell me if I've got it wrong...
The low pressure sensor monitors the feed pressure of fuel from the in-tank pump to the HPFP to make sure it's at 5 bar. If the low pressure sensor fails, then the in-tank pump runs at 100% capacity regardless of actual demand by the HPFP. Their thinking is that this could be having some adverse affect on the HPFP... possibly overloading it and making it wear out at an extreme rate (I think this is why Eric@AMS also mentioned that CP-E is looking at making a more robust HPFP replacement, one that might not wear out if overloaded by a failed low pressure sensor). They are also looking into the possibility that the low pressure sensor could be failing without being detected and are trying to determine if it should also be replaced whenever a HPFP fails. Is this correct?
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If running the in-tank pump at 100% causes damage to the HPFP, it's a MAJOR design defect on BMW's part. It's hard to imagine exactly what damage it could be doing, but there are a lot of small parts on the inlet side of the pump, so maybe it's causing fuel to blow by a seal.
The other thing that makes this unlikely IMO is that the ECU HAS to know that the sensor has failed to cause the pump to run at 100%, and they should have realized thats' what's causing the damage. If the sensor has anything to do with this problem, I'd say it's more likely that it's causing low feed pressures and starving the pump, rather than overloading it.