In Reply to: Re: Fuel pump malfunction? posted by Gilbert on January 08, 2001 at 08:28:48:
Don't know. But when my fuel pump went bad it acted similarly, but only for a day or two, then died, and, as it was dying, the dealer computer reported too lean. You can probably hear the pump running if you listen beneath the passenger side of the trunk. If its going bad it usually groans, as in bad bearings.
My 93 740i 120k. started "ailing" recently again.
After 100 miles (plus/minus) highway (I.95) driving in cold weather (Maine winter) irregular firing and loss of power slows the car to below 60 m./hour, check engine light comes on. After a minute or two the problem dissapears and in the next few minutes check engine light goes off. This repeats itself again and again on the same long distance trips. Electronic testing indicates both oxygen sensors failure. My trusted mechanic's interpretation is that it is probably failure of gas supply (lean mixture) rather than O2 sensors failure. (No engine codes detected, idling is precise like the Swiss watch). We've replaced fuel filters which unfortunatelly did not cure the problem and ordered an expensive fuel pump.
Question: Is it possible for the fuel pump to play-up like that, or do they just pack-up completely when they malfunction?
I would appreciate comments before I install a new pump.