Been busy today
I have been googling noisy fuel pumps, checking my work, and have come up with a few possibilities, some more possible than others.
I drained the tank - again - and the fuel looked pretty much ok. The bottle in the backround was from the last time I drained it.
Google reckons that a noisy fuel pump can be covered in sound deadening as petrol cools them as it flows through. Tried that as I was taking the pump out to try and clean it anyway, and also I had noticed that the pump was connected to the 8mm copper pipe by a very short piece of R9 hose. I had the thought that vibration could pass through the rubber hose, only 50mm long, and cause noise by the copper pipe vibrating against the bodywork. Very unlikely but as I had the pump out, I just lopped 100mm off and fitted a longer piece of rubber hose. I then poured a small amount of fresh petrol into each end in turn and gave it a good shake. I didn't get any muck out and the petrol remained the same colour, so not much amiss there.
If you check out post number 653, on the last page the 12mm feed in the sender unit shows that for a very good reason that I cannot remember I cut off the tube from the old main feed. This is now the return pipe and me cutting it off leaves it 10mm from the outlet pipe and filter. After reading up on swirl pots (Cheers Quagmire) the return on them is fed into the top to keep hot fuel going straight back into the engine. My return is 10mm from the outlet, so I decided to extend it. It did occur to me that the return under pressure may have/cause some bubbles, which could be sucked straight into the pump. I placed a bucket under the sender and undid the retaining ring, and found this from the lowest part of the tank?
That did shock me a bit
but not as much as the filter. I pulled some of it off and it appeared to be clumps of fine fibres, which had basically clogged the filter.
Here is a very likely suspect. I cleaned and replaced the bucket then poured a litre of petrol into tank. It came out almost black and full of bits. I tried again, same result. So, out came the seats, rear parcel shelf, speaker, filler cap, breather pipes etc, and then the tank. I took it outside, gave it all a good flush out then all back in. Sender now looks like this -
Rear seats are still all over the place but it did start, and I wandered off for a drive. Spent ten minutes getting the engine warm, then listened for the pump: Nothing, just the distant purr of a normal fuel pump. The noise does appear to have gone, and I will be cruising about a bit more this week and hoping it doesn't come back.
What a palava that was
Richard