Reply With Quotefrom theory not, as in idle it probably needs lowest fuel volume. A fuel pump in general always pumps more than is needed, the excess is fed back into the tank via the fuel return line.
fuel pump question
can a bad fuel pump have a major effect on the car's idle? if so what can it do, to what degree, and how serious it is. thank you ^.^
btw, it's an m20b25 525. 1990
Super Moderator
from theory not, as in idle it probably needs lowest fuel volume. A fuel pump in general always pumps more than is needed, the excess is fed back into the tank via the fuel return line.
3 Grand Master
I wouldnt think so either. Have you checked and found your fuel pressure is lower/higher than expected?
Oct '00 E46 330i. Feb '92 525i (departed)
i haven't done a fuel pressure check, but a mechanic said that my fuel pump is bad and that it stops working after the car is warmed up.
today i'm doing a fuel pump change to the tre-340 BMW 255 LPH Fuel Pump - TREperformance.com
i also had another question, what the mechanic said above, is that even possible?
3 Grand Master
Anything is possible. You can get dry joints on a relay. The car warms up, metal expands and there is no contact. Result: car wont start.
The trick is diagnosing the problem. To confirm I would warm the car up and jumper the fuel pump relay. If it doesnt run and you have 12V at the pump its a fair assumption the pump has had it. Maybe he did that
Oct '00 E46 330i. Feb '92 525i (departed)
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4 Grand Master
The question is how old is that fuel pump? The youngest E34 is 16 years old. Fuel pump failure in BMW is a common issue.
yesterday i did a complete fuel pump overhaul and changed to a tre performance 340 pump. i got the car started for a few minutes and in those few minutes my idle seemed cured but then the car shut off so now i don't know what the cause isOriginally Posted by Tiger
Super Moderator
not yet. i'm waiting till wednesday to go pick up a muiltimeter. best part is there's no school this whole week so i can really get down to the problem. and if you don't mind, how could that cause a problem?
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