So yes, the GS911 shows fault code 10168 - electric fuel pump faulty (most likely: fuel pump electronics/driver) not present now

Real time values:

Fuel pressure: 4500 mBar dipping to 3000 occasionally.

As usual, after cooling down for 10 mins the bike runs fine. Looking at that heatsink on the FPC, I wonder if that isn't the most likely component to suffer from heat...?!

I couldn't find Techron but I put some STP gas treatment in the tank which looks to do a similar job.

So I will try disconnecting the fuel pressure sensor and see if that cures it.

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F650GS twin - Enfield Bullet 350 - Honda XL250 Degree

Sorry to hear about your troubles Guy.

Doesn't surprise me though, you might remember that I advised you to take a spare controller and pump with you as the most likely pieces to fail on a long trip....

Lukas

No-one likes an "I told you so" Lukas...

And in my defence, various knowledgable sources including BMW themselves told me that the FPC issues were confined to the 1150/1200 bikes and did not affect the 800s...

So much for research

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Hi Docsherlock

So I bypassed the Fuel Pump Controller and the problem remains. Do you think it would be reasonable to assume this means I have a faulty pump? I am on the point of getting a new one sent from Europe (thanks Lukas!) but it would be a long wait for nothing if the problem is elsewhere.

My GS911 showed the fuel pressure wobbling at times and somewhat in line with the faltering of the engine. I figure that bypassing the FPC rules out a problem with either the sensor or the controller, right?

I don't have the facilities to test the output volume etc. and anyway the conditions that cause the fault would be hard to replicate - atmospheric pressure and length of operation. It does seem to temporarily fix things if the tank is filled so that suggests it's a temperature-related issue in the pump.

Incidentally , I ruled out the sidestand as it happens with the bike in neutral.

Any further thoughts or shall I just go ahead and get a new pump?

Thanks for your time!

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F650GS twin - Enfield Bullet 350 - Honda XL250 Degree

I should also mention that the removal of the FPC in the chain has made the problem worse which to me suggests the pump is at fault - in that now the pump is working harder at full pressure all the time.

I'm curious to know the exact function of the FPC? Does it provide a varying voltage to the pump and is this to maintain a constant fuel pressure? ie it makes up for pump inconsistencies? Or is it more complicated than that?

And any suggestions why altitude would cause this issue? Is the pump working harder to conteract the ambient oressure?

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F650GS twin - Enfield Bullet 350 - Honda XL250 Degree

Bypassing the FPC doesn't really help distinguish the sensor/controller contribution.

Unplug the sensor from the end of the fuel rail and see if that helps.

However, it does seem that the problem is the pump itself given the history and GS911 reading.

How much extra is it to buy the FPC, pump and fuel pressure sensor as opposed to the pump alone? If you are having something sent from Europe you better be damned sure the diagnosis is spot on or you may have to wait for another component; for a couple hundred bucks I'd buy all three and get 'em sent at the same time and swap the whole lot out; if you can narrow it down when you get the components, then sell the good stuff or keep as spares as you will probably need 'em at some point anyway - it's a BMW.

However, from what you have written, my money is on the pump itself as it can't run properly flat out (removing the controller makes problem worse, worse when hotter i.e. low fuel).

The FPC varies the pump output depending on various sensor inputs so it is not working flat out all the time; bypass it and the pump runs at max all the time.

I think the problem being worse at altitude is a combination of your hypothesis (working harder to maintain pressure) and the pump running hotter up there, if my basic physics serves me correctly.

Good luck with it.

DS

PS don't forget to mention this in future ads for your bike - karma is a bitch; but actually, in these bikes, having a new fuel pump is a good selling point at your mileage. That's karma for ya.

Thanks for all that! I tested the pressure sensor as described in my Haynes Manual and the impedances are correct. I then disconnected it and went for a spin and no change although I haven't been able to give it a long enough run to be totally sure yet. The person who is sending me the pump and controller may also be able to send me a sensor so I should be covered...

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F650GS twin - Enfield Bullet 350 - Honda XL250 Degree