94 325i E36 Fuel Pump noise?

[ethemaestro]

I have a constant "whine" sound that seems to come from the rear passenger seat area and undercarriage. This sound is only heard when the car is running. It does NOT vary with RPM's, it is just a constant high pitched electrical noise almost like feedback through a radio (but occurs even with the radio off and is NOT coming from the speakers, its just the type of sound). I can also hear it from the fuel filler door and undercarriage. Have had others say it is the fuel pump going bad, but I have no other issues. Car starts right up everytime, drives fine and the engine is as responsive to the gas pedal as ever. No hesitation or cut outs at all. Just this noise that is annoying and troublesome if it IS a fuel pump going out I don't want to end up stuck somewhere. The previous owner said it has sounded like that for a year or more and he just ignored it.

I thought the fuel pump would turn on and prime with the key just turning the car ON (without starting it) but there is no noise at all when I turn the car on, the noise only occurs when the car is started and then it is constant until I turn the car off.

Anyone ever experience this?

[bmwdirtracer]

Some BMWs do not "prime" with key turned to on position, and wait until there is timing info from a turning engine to activate the pump. It's very likely that your noise is from the fuel pump, but that does not necessarily mean that the pump is failing.

Your fuel pump lives under the back seat: pull up on the front of the seat bottom to remove it - if the noise is markedly loder, the fuel pump is the noisy culprit. When's the last time you changed your fuel filter? A clogged filter can make a pump noisier, because the pump is fighting against a clog. However, some pumps are just noisy. It is also worth noting that ethanol kills fuel pumps, and that the fuel pump pickup could also be dirty and clogged, inside the tank.

[ethemaestro]

THANKS! I suppose I should try the filter first. Can you tell me if the E36 has it located in the Engine compartment or under the car?

[earnestbunbury]

For anyone that's looking at fuel pump or fuel supply noises... I had in my '93 325i e36 an adjustable fuel pressure regulator and was a bit high at 56 to 60 psi w/o vacuum and that caused the return hose and pipe to rattle. Taking off the cover over the driver side access hole revealed a hose vibrating and it sounded just like a whining pump (but was coming from the non pump side of the tank, the return side). If one's fuel pressure regulator is malfunctioning and allowing too much pressure, then this could be the solution. Good Luck