635csi '86, can you hear fuel pump?

Can you actually hear the fuel pump running when ignition set to "on" position? I can't, and engine isn't getting fuel. Before deciding the problem is a bad in-tank fuel pump need to know if other owners can hear their fuel pumps running when car isn't running...

Thanks! Dru

Agreed.

Undo the rubber hose that comes from the bottom of the fuel pressure regulator. Hold a (preferably glass) bottle under it and have someone else run the engine briefly. You should get fuel.

I'm not sure about your car exactly, but on my 'other' car of about that age - not a BMW - with EFI by Lucas but based on Bosch, the pump only starts running when the starter circuit is energised, or the AFM flap opened. It then latches on. The starter circuit also bypasses the pump series resistor while in operation.

My old 735i (same engine) used to leave an injector open or a one way valve leaked, so if the car was left for a few days the fuel line was empty you could hear the fuel pump for a few seconds (followed by little pulses until it was happy) as it refilled the line. If you disconnect down stream of the pump (at the fuel filter perhaps) then it should pump fuel when you switch on the ignition.

Warning - do not smoke during this operation!

Fuel being present isn't the only thing - it must also be at the correct pressure. IIRC, the most common reason for the line losing pressure quickly is a worn fuel pump. If an injector or injectors were leaking this would show up as a rich mixture and poor fuel consumption especially at low throttle.

Hey all.

Thanks for the info and help.

I had the car fixed today at Brownfeld Auto in Manhatten. They said both pumps were dead. Replaced both pumps for $650 USD.

So good news is that my sixer is up and running again. Bad news is only the price tag. Could be worse I guess :0

Dru

Dave Plowman (News) wrote: