When my fuel tank is nearing empty, I can hear noises coming from the back of the car. The best way I can describe it is like a groan for 2-3 seconds, and audible above all the other noises in suburban driving. It repeats at variable times from 10 seconds to 2 minutes.

Today, for the first time, I noticed it after I had switched off and locked the car. I could hear it 30-40 feet away, and then it stopped.

So I started the car again and listened for it underneath, near the fuel pumps and accumulator. Nope. Not from there. Opening the boot/trunk I found it was loudest on the left side hidden in front of the panel covering the fuel tank. I then removed the fuel cap and let the pressure escape - the noise stopped.

Is there some sort of pressure relief valve hidden behind there? The fuel check valve? How do I remove the panel to check it out?

Also, my fuel pumps are quite noisy, and the buzzing noise is audible all the time while driving. One has a nasty noise like a little ball bearing being crunched every now and again. Sounds like replacement time. I have yet to change the fuel filter, and reading this forum I should probably expect some improvement if it is clogged. With new pumps, should I expect them to be inaudible in the cabin while idling/driving, and will the car still run if one pump fails?

Any ideas would be greatly appreciated.

__________________
Steve

1982 380SL

Previous cars of interest
1981 500SE
1976 Jaguar XJS
1974 Rover 3500
1953 Riley (before they became scarce)