380SL "groaning" noise from fuel system
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.
Previous cars of interest
1976 Jaguar XJS
1974 Rover 3500
1953 Riley (before they became scarce)