Noisy fuel pump

[niles1]

I live out here in las vegas and at the moment it is over 110 degrees, I commute on my K75c 200,000 plus miles great bike but the fuel pump makes a really high pitched whining noise when i get off the throttle to exit the freeway, any ideas to the cause ??? by the by this is my third new fuel pump in less than a year.. the original one lasted for ever and the new ones were apparantly junk...

[98lee]

Check your fuel filter (even if it's new). Once it is dried out inside you should be able to blow through it with no resistance (no backpressure).

Also, remove the pump and inspect the tank below the filter for signs of goo or crud beneath the pump.

Check the pump filter sock or cup (depending on which style of pump you have).

[jpberens43639]

Also,what make of fuel pump are you putting in there? Is it BMW or something else? Sorry, at the price of the BMW pump, WOW!!!! I'd use something else. There's a couple of good swap out's that will work fine.

Most often a whine is caused by vibration. Could just be the way pump is held in the vibration damper boot.

[deilenberger]

Hopefully if these were BMW pumps you've been replacing them under the parts warranty..

Something is causing the pumps to go bad. The noise is a big clue - it's the pressure relief valve in the pump blowing off due to a restricted output. If I had to guess - it's either the fuel filter, or the fuel pressure regulator. If you want to avoid throwing parts at it - you could hook up a fuel pressure gauge to the fuel rail and see what the pressure is, then move it to the pump output. The manuals will give you the correct spec's.

[BUDDINGGEEZER]

The K100/K75 fuel pump will pump over 100psi , the fuel pressure regulator reduces this to 36 psi.

Ralph Sims

[98lee]

I would think that if the regulator was bad it would run like crap. Way rich or lean (not sure of failure mode).

But checking the fuel pressure would be the second or third thing I would check after the fuel filter and tank. Also possible kinked or bad fuel hose to fuel rail.

[kayseventyfive]

I would think that if the regulator was bad it would run like crap. Way rich or lean (not sure of failure mode).

My regulator failure mode was a constant 21 psi. Ran like crap. It was probably something stuck in the regulator valve seat, because a blowgun made everything OK.

[deilenberger]

I would think that if the regulator was bad it would run like crap. Way rich or lean (not sure of failure mode).

That's why I suggested it be checked AFTER the fuel filter is replaced.

But checking the fuel pressure would be the second or third thing I would check after the fuel filter and tank. Also possible kinked or bad fuel hose to fuel rail.

Yup. Kinked hoses can do it also, especially if the formed shape ones BMW used are replaced with some generic FI hose. There is a reason BMW shaped the hoses like they did.

[98lee]

I'm just wondering if the original pump failed because of the dissolving vibration damper.
Pump and damper changed but tank not cleaned out so next pump sucks up debris/goo and fails shortly and now this ones doing the same.

[niles1]

Hello.
Thanks for all of the info I shall look into some of the options put forth in this discussion and yes they were all BMW pumps and under warrenty but for me that is not the point but I do like the idea of looking for the faults somewere else around the pump which could be causing this issue for me.