Fuel Pump Buzzing after Engine Shutdown

Post Sun Jul 07, 2013 7:10 am

I have just noticed my fuel pump is still buzzing, with a slight clatter, for about 3-5 minutes after engine shutdown.

No noise from the fuel pump when driving though. At least I can't hear anything from the fuel pump when the engine is running.

I have had intermittent cutting out problem too. Always happens when driving. The engine doesn't die, just losses power momentarily (a fraction of a second). The fuel flow gauge drops to zero when this happens.

Are these good signs of fuel pump on its way out?

Thanks

PS: the car is 318i with M40B18

Post Sun Jul 07, 2013 8:42 am

The fuel pump shouldn't be running at all if the engine isn't spinning, even if the ignition is on.

Fuel pump is triggered by the ECU, which is told to turn on the fuel AND spark when the engine is spinning. It knows the engine is spinning by the CPS, a sensor at the front of the engine. Normally engine cut-out issues are traced to that sensor, but I've never heard of one keeping the fuel pump powered on.

Next time it happens, open the bonnet and see if there's a buzzing noise coming from the Idle Control Valve.

Post Mon Jul 08, 2013 12:10 am

I walked around the car in the garage trying to locate the source. Noise is definitely from rear RHS area and as far as I know, only fuel pump can make such noise there.

After some Googling I found this article, which suggests internal check valve in the pump may be the cause:
http://www.pelicanparts.com/bmw/techart ... l-Pump.htm

Also found a suggestion of sticky relay. Hopefully my mechanic is able to have a look at the car pretty soon so I don't get stranded in the middle of nowhere