During our trip up the Antrim Coast last Saturday, ComberJohn said something along the lines of "Hey boy, your fuel pump sure is noisy" to which I replied "apparently they are all like that". Dont think ComberJohn bought that. So, having been made paranoid, I took a sound level reading with the tank empty and got 34db. Then I took out the pump, checked rubbers & filter and all seemed ok. Looking in the tank, I noticed a length of rubber laying at the bottom, see pic 1. It turned out to be a cushion of sorts between the fuel pump bracket and tank wall. Put back in place, see pic 2 and thought that might quiten things down. New sound recording got the same 34db! Do I just accept its noisy and watch small children run for cover or is there something amiss?



Black rubber thing



Now back in place on right hand side

They all behave like that, sir.

Especially when the fuel level is low
and the top of the fuel pump is exposed above the surface.

Added to that also the tank act as a resonance chamber.
As the fuel level drops, the sound level increases.

Interesting thread, I found exactly the same bit of rubber laid on the bottom of the tank as well years ago I asked the list if anyone had an idea but no solid leads, I even asked the mechanic at the BMW bike shop I buy my bits from, both looked knowledgeably at it and said never seen one before. Your suggestion looks like it might be the solution does everyone concur?
Regards,
K-BIKE

In the different forums it`s been a lot of owners who have found this pieces in the bottom of the tank.
And a lot of headscratching.....since it don`t exist a part number.

This won`t be the last one....................

The previous owner of my now sold K100 apparently found it in the tank and put it on the float arm. When I saw it there I thought it was in its correct place and was for ages telling people that was where it went. Felt like a real fool when the truth emerged.

Not the first one, it was also a couple owners in another forum that came to the conclusion that the float arm must be correct place..............some years back.

I only noticed because the one on the left hand side of the bracket was still in place otherwise god only knows where I would have put it (probably in a drawer!)

draw would be a better solution than floating round in the tank ....poor old rubber bits

Due to the type of technology involved, i.e. its a roller cell pump it becomes noisy after a while. Ive found from experience that its time to replace the pump rather than be stranded in the boondocks. This pump is not unlike the injector pumps used in automobile applications in fact many of the pumps from German cars will work OK in your bike as long as the pressure rating and size are the same. There are even aftermarket pumps that will work just fine and at much reduced cost. Ive just replaced the injector pump in my Audi A6 for that very reason. Its a Bosch pump but its made in Poland, go figure.

When I turned the key last night I was not met with the usual cacophony of the fuel pump. Tested the four pin connector and voltage only measured at the white wire. All fuses checked with meter and ok. Could it be the relay and if so which one is it?

While I was at it, i pull the pump out and tested it, surprising how quite it is outside the tank! Reversed the polarity to flush it out backwards and tiny metallic flakes now visible in the filter, not a good sign me thinks.

GMcQ

No that usually isn't a good thing to see, it often means that something is preparing for a self destruct effort.

Was thinking that Rick, pump top of the wish list. Turned out to be the side stand switch not working. Disconnected the connection block and using a wire joined the two terminals and the pump fired up.

GMcQ

Well, replacement pump fitted. The difference in sound is unbelievable! There is no sound The banshee is gone. Cant wait until ComberJohn hears it, or rather, cant hear it! With the squealing gone, my bike sounds great, couldn't appreciate it before.

Question: My bike seems to be running better; ticks over better and acceleration is smother. Is it possible that the old pump was delivering fuel at a low pressure or is it just the placebo effect?

GMcQ

Low fuel pressure will make them a bit ornery.