Fuel pump whine, hesitation

nickyy · Post by **nickyy** » 30 Mar 2016, 22:04

I have an 88 740 turbo. After starting, car runs fine for a minute or so, then experiences what I feel is fuel starvation, with my having to strongly press down on the throttle in order to keep the car moving.

I replaced the fuel filter, main fuel pump and fuel pressure regulator.
New fuel pump appears to be constantly on and makes a loud hum.
Fuel pressure is 35 with FPR hose connected and 45 with hose disconnected.

None of these repairs has fixed the problem.

Any suggestions?

Thanks,
NIck

93Regina · Post by **93Regina** » 31 Mar 2016, 07:40

nickyy wrote:...fuel starvation, with my having to strongly press down on the throttle in order to keep the car moving...

Bosch's EFI does not have an accelerator pump, so unless the pedal is to the metal, then if fuel starvation was the issue, there would be "popping noise," due to lean mixture. So, put the pedal to the metal, and report back.

lummert · Post by **lummert** » 31 Mar 2016, 08:24

Engine temperature sensor can cause issues. This is the sensor that can be seen by looking down between intake runners 3 and 4. This car has an in-tank pump that if not operational will cause the main pump to make excessive noise.