Fuel pump hum/whine

[Andy Cunningham]

I've just bought a used 12000 mile 1150GS in excellent condition with a full BMW service history. So far I'm delighted and am becoming acquainted with the various noises the beastie makes.

However one noise which I don't remember hearing on test rides of other Beemer twins is a constant hum/whine from the fuel pump. It's not very loud but I can always hear it when I stop at junctions etc. The noise is there regardless of the volume of fuel in the tank.

So my question is "do they all do that sir?", or should I be worried.

Andy

 

[Deadskin]

Hi Andy
Check your petrol pipe clips and the high pressure hose down by the right throttle body.
My dealer changed my clips to the jubilee type

M

 

[Andy Cunningham]

Yeah I read some of the posts about fuel lines, but I see no evidence of leaks and the rubber fuel lines are attached to the plastic pipes with jubilee clips.

When I got home today I took my lid off with the bike still running and stuck my head next to the tank where the fuel pump is. I could hear a continuous whirring/huming noise coming from the pump. It didn't sound bad or terminal or anything, just the noise of a working pump.

Andy

 

[Malcolm]

"They all do that Sir"

Heard that somewhere before?

This is getting repetitive

 

[Mick Fagan]

I'd be a bit worried as it could be the first sign of a ruptured fuel filter, which is inside the tank. Or maybe a fuel line inside the tank not being connected quite correctly. This latter problem isn't serious yet, but if the line does drop off then the bike will stop as you'll have no pressure.

I'm led to believe that BMW retain the fuel filter inside the tank in case the filter ruptures, in case this does happen it only leaks back into the fuel tank itself.

When you first switch the bike on the pump should whirr loudly as it gets pressure up, then the noise stops until the pressure drops again.

Also if you are running the fuel pump non-stop, then it may burn out, they are quite expensive.

Mick.

 

[DrAlf]

Andy.

Mine has also been suffering from the fuel pump whirling noise since I got the bike. I have checked out a few threads on the problem on this forum along with the Advrider forum and also the R1100S Pelican parts forum. Some people claim that it is a sign that the fuel pump is about to die but others say that it is nothing to worry about. I have covered over 6000 miles with the noisy pump and its still going so I guess it’s nothing to worry about. Regardless of the amount of fuel in the tank, I find that sometimes the noise will be more noticeable than others and very occasionally it can be so loud that it becomes quite annoying. If you bought the bike from a dealer, take it back and get them to sort it. If you bought the bike from a private sale, live with it or contact Motorworks or the like for a replacement pump. I did hear a rumour that the fuel pump is the same as some VW cars, I have no idea whether this is true or not though.

HTH

DrAlf

 

[Roge]

Ther is something inheritantly wrong with a bike when the noisest thing is the fuel pump. The cure is a y-piece and end can, lovely.

 

[Mick Fagan]

Andy, I have just walked out to my bike and turned the ignition on. There is a whirr for a few seconds and then silence.

Ever since new it has been like that. All of my friends that own 1100/1150 twins have the same noises that I do and I know quite a lot of people on BMW twins.

The only time I've heard the fuel pump going whilst riding is when at a set of lights when the tank was extremely empty, I could hear the pump going on and off searching for fuel to keep the pressure up.

I would say that you do have a problem and I would say the chances are that it is either a ruptured filter, or, an inside the tank fuel line, not connected correctly!

Mick.

 

[Andy Cunningham]

Also if you are running the fuel pump non-stop, then it may burn out, they are quite expensive.

Sorry Mick, but the above makes no sense to me. If the fuel pump isn't going all the time then there won't be any fuel going to the cylinders. The fuel pump should be going all the time, it's just a question of how much noise it should be making.

On balance I've received juat about as many responses saying "mine does that" or " they all do that", as I have "oh my god your pumps about to explode get down the dealers pronto".

My fuel consumption is around 300 km before low fuel warning and there are no visible signs of leaks, so I'm inclined not to worry. When I get the opportunity I may pop by my local dealer to get them to have a listen.

Thanks to all those who have responded.

Andy

 

[The Mechanic]

Electronic fuel injection

For the fuel injection system to be able to supply a constant pressure of fuel for the injectors to release into the cylinder at the instruction of the ECU (computer) the fuel pump has to be running all the time. If you have a fuel injected car then start her up and stick your head close to the fuel tank, you should here all kinds of whirrings and the splashing of returning fuel. Most (nearly all) EFI (electronic fuel injection systems) employ the recirculating fuel method. The fuel is pressurised by the pump approx 34-38 psi. constant, there is a fuel pressure regulator that bleeds off the pressure down to perhaps (for example) 32 psi and this is what the engine will run off under normal load. When you accelerate the pressure regulator via a vacuum connection and the ECU in conjunction with an MAP (manifold absolute pressuresensor) will allow more fuel pressure to be applied to the injector, this coupled with a longer open signal from the ECU (injection width) produces a richer mixture (like an accelerator pump on a carb) and takes out the potential for flat spots and hesitancy under load.
The reason your pump sounds noisy could be that it has become detached from its anchorage and is vibrating against the tank, or that it is just a noisy pump, its lasted so long so it might be ok.
These things are massed produced so expect a bit of difference between bikes, but you will only be really sure by having an expert (someone who knows these things inside out) look and listen to your machine.
The quickest check is to have the fuel line pressure checked, if the pumps on its way out the pressure will be skew whiff.
If your bike performs perfectly normal then maybe you could just ride on in (ignorant) bliss.