Fuel Dilvery Problem

[glennis]

Hi,

I need some help on a recurring issue. I have a 2006 R1200 GSA with 60k miles on it. About 3 months ago while in Thailand a problem developed which resulted in the bike never using all the available fuel in the tank. I ran the bike to empty on the gauge and continued riding until the bike stopped which was a few miles later. I then filled the tank and could only get in 26 litres at most. I have done this a few times to confirm it is not a fuel gauge problem. The guys at BKK Motorrad Thailand replaced the fuel pump motor (not the whole pump assembly) and the problem seemed to be resolved.
Everything seemed fine for the next 2000 or so miles and after shipping my bike from Malaysia to South Africa by sea the problem has returned. The engine idles fine and operates normally except in high gear under heavy load and high revs where it sounds/feels like its starved of fuel.

I have done some investigation and have the following to report.

- No fuel is flowing back to the left hand lobe of the fuel tank via the connecting internal hose which can be seen if the fuel pump assembly is partially lifted out with the pump still submerged in fuel

- I disconnected the return fuel hose from the fuel regulator, which runs to the right side of the tank, to check the return fuel pressure and it is very low. Fuel dribbles out of the hose when the white plastic inside the quick connector is pushed in. To quantify, the flow rate is about 200ml/min. I don't think this is sufficient to operate the venturi pump which moves fuel back to the LHS of the tank. So I conclude that the fueling system on the right side is okay.

- The fuel pump motor was replaced 3 months ago and is essentially brand new. I cannot believe this is the problem again.

- I borrowed a brand new fuel pump controller. This did not rectify the problem.

- Checked the voltage from the ECU to the FPC and this at battery voltage. So problem not related to ECU or whatever BMW call it.

- I have inspected the fuel lines for kinks. There is very very slight thinning where the pipes bend but not enough to reduce the flow that much.

So by process of elimination the only remaining parts that I have not tested is the fuel pressure regulator and the fuel pump assembly (the whole plastic housing which I understand contains an internal filter). How likely is it that the internal filter is blocked and can it be serviced?

Before I let BMW in South Africa sell me parts I don't need I like to get some feedback from you wonderful mechanical masters on UKGSer.

Cheers

 

[harry]

Have a look here, www.ukgser.com/forumsshowthreads.php?=286648

hope it works, you can google it too

 

[glennis]

Fuel Delivery Problem

Oh no, spelling error in title. That's supposed to be 'Delivery'

 

[Magwych]

Harry your link doesn't seem to work.

Glennis, sounds like you have narrowed it down to 2 logical choices.

If the fuel pressure regulator was stuck open it would allow more fuel to flow back to the vaccuum lift pump in the right hand side, it was stuck closed it would over pressurise the injectors.

When you tested the return flow to the vaccuum pump, you were running the engine above idle revs to ensure the fuel pump was on a higher delivery rate?

I replaced my pressure regulator a short while ago and it did releive an asthmatic feel it was getting, but I was not suffering any problems with the return pump.

 

[glennis]

Magwych - thanks for you reply

Yes, when I tested the return flow I revved the engine which in theory should have increased the return flow rate from the fuel pressure regulator. However no noticeable increase in flow rate could be seen.

Also if the regulator on my bike was stuck closed and the fuel injectors were over pressurised I would not expect a small but noticeable reduction of power under hard acceleration in top gear.

Can anyone suggest a method for testing fuel pressure/flow out of the fuel pump assembly into the fuel pressure regulator?

 

[Bendy toy]

I replaced my pressure regulator a short while ago and it did releive an asthmatic feel it was getting, but I was not suffering any problems with the return pump.

Mine also feels asthmatic which I had put down to the Akraprovic exhaust system. How can I diagnose if the fuel regulator is a problem on my bike? Do I need a GS-911?

 

[glennis]

Magwych - I had a look on Advrider and could not find a thread for cleaning/replacing the fuel filter on an R1200GS. Could you be so kind and post the link.

Cheers

 

[Magwych]

Its in there. There are a huge number of handbags being waved around, much like ,ost thread on the site, don;t knwo if I want to go back to that place.

It boils down to the fact that although their is a separate filter element, it is glued inside the pump plastics and does not seem to be accessible without detroying those plastics. I assume you are think that there is some form of blockage on the supply side?

 

[Magwych]

Here ya go Glennis, I found this in my browsing history: http://www.advrider.com/forums/showthread.php?p=18518953&mode=linear#post18518953

 

[glennis]

Yeah, Advrider's search engine ain't so good.

What I think I'll do is drop it in to BMW get them to diagnose the problem. If they suggest a new fuel pump assembly I'll attack the old one and attempt to clean the fuel filter before I buy a new one.

So, one last call out - Does anyone have any experience in servicing the internal fuel filter inside the fuel pump assembly????

Cheers

 

[Magwych]

Might be worthwhile checking that the fuel line was securely re-attached to the pump when the pump was replaced?

 

[glennis]

Thanks Magwych, that will definitely point me in the right direction for removing the filter without completely destroying the whole assembly. Usually I break things like this trying to figure out how they open. Only once I've broken it can I see how I should have done it

 

[glennis]

So, I've still had no success in rectifying this issue of fuel not transferring from the right side of the tank to the left. I back flushed the non-servicable filter inside the pump flange and a whole lot of crap came out. I reconnected everything and I still have almost no fuel flow into the right side of the tank from the return line of the fuel regulator. I suspected low fuel pressure from the pump due to a clogged filter and so bypassed the filter and installed a new inline filter. The problem still exists. I have now connected a pressure gauge to the delivery side of the fuel pressure regulator and it is indicating 3.5bar.

Does anyone know what the fuel pressure on the delivery side should be? I remember reading somewhere that 3.5 bar is about correct. If this is correct could there still be a problem with the fuel regulator or the fuel line to the right side of the tank. Not sure what else might be the problem

I really need some help here.

Thanks

 

[harry]

Glennis, Have you looked at the workshop manual Fuel System drawings?

There is, in the tank, a very basic pump which is called the Sucking Jet Pump, there are quite a few reports of this failing, so the fuel fails to transfer and you get the probs you appear to have.

Good luck

 

[glennis]

Thanks for your response Harry. I have swapped out my tank for a known working one and I still have the same problem, so there is no issue with the pump/lines etc. I also removed the quick connectors and the short rubber hoses to check if the flow through those parts was okay and no problems there. The only remaining item now is the fuel feed lines and the pressure regulator. Unfortunately there are no replaced parts in South Africa at the moment and expected delivery is 2 weeks from Germany .

I might try buying a generic fuel regulator and run my own hoses from the tank etc. As far as regulators go are there any different types or are they pretty generic?

Cheers

 

[Magwych]

The fuel pressure regulator is IIRC 3.5 bar. It is stamped on the body. It does a fairly simple job, fuel fed in is passed out, until the pressure exceeds the limit, in which the excess pressure is relieved through the return pipe. I would guess that any 3.5 bar regulator with the same connections would do as a test bed. Don't forget that although the returned amount might be low, it is at 3.5bar, i.e. over 50psi; so can be made to do a lot.