Singing fuel pump

Beak Freak

Beak Freak

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Oh great collective brain, I am hoping someone on here will have the answer to my singing fuel pump.

Bike is a 2000 850GS, been chipped and running a y piece and Remus. The bike was stood for a long time and as part of the work to get it back on the road, the tank was removed, new pump, filter, hoses, sender unit etc. Tank was flushed and all was well with the world.

Been used for around 3 months no problems, in fact, was running sweetly.

about 6 weeks ago, I did a gear box oil change and replaced the spark plugs (I decided to give the Brisk plugs a go). All fine, bike was running even sweeter and fuelling and tank range was normal. After a couple of days the pump started to whine and got progressively louder. tank off, filter checked and all seemed in order.....now this is where it starts to get weird.

Because most of my riding is on Guernsey it is slow and sitting with the singing fuel pump was starting to hamper my usual calm nature:D, I decided to get a new pump. Pump was fitted and all was back to blissful silence. Two days later it started to whine again and is now singing like the proverbial canary.

I changed the plugs back to Bosch platinum (as this was the only change I had made prior to it singing), but it made no difference.

Both filters are clear, hoses aren't crimped or split.....any ideas welcomed as the noise is slowly driving me nuts!
 
Does the singing vary in tone/pitch according to how much fuel in the tank.
 
Nope, pretty unbearable at all volumes!

It does change slightly from idle speed to when the throttle is applied, but its a step change rather than progressive (if that makes sense)
 
In light of my well documented whining fuel pump in the Congo last month, albeit on a r1150gs, I shall be following this with interest!


Sent from my iPad using Tapatalk
 
May be unrelated,

Many years ago we used to hear what sounded like a cow mooing at odd times of the day or night.

pretty normal, except we live in a town with very little bovian activity.

After many months i finally tracked down the source of the noise.

it was the fuel tank venting excess pressure through the fuel filler cap -

The diaphragm / mech inside the cap had either gone hard or wasnt sealing to well and acted like a reed.

The cost of a replacement cap vs the frequency of the noise meant we lived with it ...


Are you sure it's the fuel pump and not a symptom of something else ?

Seem strange that you had the noise, changed the pump and it returns ..

sounds like a blockage somewhere and your hearing the efffect of the pump straining or working harder than it should ?

Or it could be a harmonic .. the pump is running normally, and your hearing the normal rotation / pumping harmonic amplified from another indirect source

My hexhead sounds like a bag of spanners sitting astride it, but move one step to the left or the right and it sounds very quiet (now lol)

I'm convinced the cockpit / beak arangement acts as a horn and amplfies normal sounds to a greater level
 
Thanks for the suggestions so far, but I don't think it any of these.

I have owned the bike from new so I know what it should sound like. This is a loud high pitch whine, very audible even with a lid on. Other people can also here it when they are nearby...with a lid on!

It makes no difference if I open the filler cap while the engine is running.

My confusion is largely because it just started from nowhere and then was quiet with a new pump fitted, but became noisy within a couple of days.

Is there any chance it is linked to the Moronic? Could opening full throttle cause something to stick and demand more fuel, leading to strain on the pump? I am obviously clutching at straws on this one!
 
How positive are you that the noise is coming from the pump? Does opening the fuel cap change the pitch or volume of the noise? I would expect it to, if the source of the noise is in the tank itself.

Maybe get your ear close to the fuel pressure regulator.

Anton Largiader made this comment on another forum:

"If the fuel lines are connected backward, or one of the disconnects is not fully connected, the pump will whine because it is blowing off the overpressure through its internal valve."
 
I am not that experienced with BMW'S not having owned one until my recent purchase of an 1100GS but what I noticed that when I changed my fuel filter recently the pump is a hell of alot noisier, I put my noise down to the fact it may be touching something of I put something back in slightly a different position...

Not much help I know but just a thought...
 
Beak Freak said:
Is there any chance it is linked to the Moronic? Could opening full throttle cause something to stick and demand more fuel, leading to strain on the pump? I am obviously clutching at straws on this one!
Click to expand...

Fuel pressure is at a set pressure, 3 bar, throttle position has no affect on it.
 
Hi gog

Surely if the fuel lines were connected backwards then it wouldn't run? I have quick release fuel line connectors set so that they can only be connected one way. Also I can't understand why it would be fine for a couple of days and then start again?

I think I am getting to the point where I will have to take it all apart and check everything over, but I am confused by the way in which the issues developed...doesn't take much though!
 
was quoting someone else (far more knowledgeable than me)

shouldnt be that hard to first confirm it is the pump that's making the noise. if it is, and you've changed the pump, filter and all the internal pipework (including the U bend) a few months ago, that should effectively rule out internal blockages causing both the old and new pumps to whine. that would suggest then checking the external pipes from the tank via the regulator to the throttle bodies. if releasing the cap doesnt stop the noise, rules out vacuum buildup due to blocked breather.

unless the tank wasnt flushed out properly, or liner delaminating causing the new filter to become blocked prematurely.

either way i guess you're going to be in the tank again soon...
 
Sorry guys been away for a few days. External fuel lines are a good shout. I have been focussing on stuff before the pump, but I guess a blocked injector or line could cause the problem.

I will have to wait for a dry weekend as I have no workshop, so should be sometime in May!
 
Hi Roger

Do you mean the rubber end cap? If so, then yes. Brand new.

The most confusing thing of the whole annoying incident is that after the second new pump was fitted, it worked fine....then after a couple of days it started "singing" again...dashed confusing!
 
Put the old pump back in .

See if it still whines? if it dosen't ... it may not be your pump.

The pump you replaced it with? new, SH, pattern, oem?
 
Beak Freak said:
but I guess a blocked injector or line could cause the problem.
Click to expand...

A blocked injector will have no effect on the fuel pump noise, as the injector is closed for most of the time and only opens for a fraction of a second.

A blocked line is easy to diagnose, have the return pipe open and see if the fuel is being returned. I think Roger says the flow should be around 2 litres a minute, you'll need him to the exact figure, but it should be a healthy flow and not a dribble.
 
Hi Santa

Another new one! This time from Motorworks, not an ebay offering. Cant get past the fact that it was fine initially and then started singing. Will try and look at the fuel lines next weekend....weather permitting.
 
Still not had a chance to strip down the tank internals, but the singing continues! Although the other day it primed as normal and only started singing about 30 seconds into the journey.
The singing doesn't alter with the amount of fuel in the tank, though it does change pitch with the throttle. It seems to be a two step process, less shrill at idle, but pitch increases once you open it up a bit. Its not progressive, just annoying or very annoying. Does this provide any clues? It makes my simple brain think it is more likely to be electrical??
 
Nippy Normans supply Touratech, Wunderlich, Desert Fox and many other makes of accessories.
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