Buzzing from around fuel tank

[dlpalumbo]

I've recently noticed an electrical buzzing that has gotten progressively louder in my 1990 C4. It seems to loudest in the vicinity of the fuel sending unit, near the relay box. I know its not the brake system pump. I thought it might be the fuel pump, but I had never heard it so loud before. Also, it doesn't run when key is on with the engine not started. Only with engine running. I would think the fuel pump would run with the key on. I disconnected the sending unit, but buzz persists. Any ideas??

Just trying to nip it in the bud, thanks for help,

Dan

[TMc993]

If the noise you are hearing is coming from slightly right of the centerline of the car and if, when you are in the car, the noise seems to emanate from the passenger-side foot well, it is the fuel pump.

If I remember correctly, when you turn the ignition on, the fuel pump runs momentarily to pressurize the system, but then does not actually run continuously until the engine is started. So, it is logical that you would not hear the pump running in the ignition-on-but-engine-not-running mode.

While a buzzing pump isn't a good thing, it isn't necessarily a sign of immenent failure either...Mine has been buzzing for over a year and the car runs fine....Yeah, it'll fail eventually, but all fuel pumps fail....Eventually.

[dlpalumbo]

Thanks for help. After reading several posts, I think its probably the fuel pump. Could be the isolaters have eroded. I'll check it next time I'm under it.