Tank leak around fuel pump assembly

2004 R1150RS
I am trying to stop a leak around the attachment of the fuel pump assembly where it is attached to the inside of the tank. I believe it is the large O-ring around the opening. I have replaced it and it still leaks. It seems to me that the ring does not compress at all when I tighten the 6 hex screws. They seem to bottom out before the ring is compressed. I have tried unsuccessfully to find a larger diameter ring to stop the leak. I don't feel it is the fuel line hoses. But, who knows. Is there anyone who might have a fix for me? I want to have it fixed before the Rally.

No magic here. Its either at the o ring or its not but because you don't clearly say which...
Did you use a new BMW O ring? Wrong materials, slightly different diameters can be an issue.
Are all fasteners original or have you or some prior owner changed something?
Is it original hose? If so, its old; if changed who knows if whoever did it used proper spec hose- many buy wrong stuff.
All fittings in good shape?
Not enough info for a definitive answer from me but perhaps an owner who has had a spontanrous leak can shed some extra light on this, I can tell you that plenty of folks with bikes this age have had hoses eaten all to heck by current ethanol gas crap. Any time you find ethanol free fuel at a sane price its worth using, especially if you store the bike a lot between uses.

The hoses around the fuel pump can get soft and develop pinhole leaks. The ethanol eats away at them. I'd say new oem hoses and clamps

Thanks for the advice.
I did use a BMW OEM o-ring. I will inspect and try the hose replacement. It is impossible to see the leak since it is so covered up.
I will try anything to get rid of this annoying leak. Thanks

17butler said:

Thanks for the advice.
I did use a BMW OEM o-ring. I will inspect and try the hose replacement. It is impossible to see the leak since it is so covered up.
I will try anything to get rid of this annoying leak. Thanks

Click to expand...

How about if you remove the tank and inspect it while it's on the bench. You should be able to see the weeping better. If it doesn't leak on the bench then it may be the external fuel hoses or fittings when under pressure.

Although the vent lines breakdown and leak, usually that shows at the canister or down by the right foot peg, not near the tank plate.

Darn, I knew I should have just left it on the bench for awhile. But, no, I think I know exactly what it is.
The hoses are original and sure could be the problem. Do I have to order BMW OEM hoses? Or will some from another source that are comparable be sufficient?
My O-ring was expanded when I took it off of the tank. Now, it is smaller than the groove that holds it. Should I go ahead and purchase a new one, or soak it in fuel so that it expands again??
I sure am learning a lot here.

I hate re-doing jobs that I thought were finished. If it were me, I'd replace with all new stuff, so I'd have no doubts about the job done and materials used.
Good luck.

tank leak I been thru that tried everything

Finally found out there was a very small crack in tank just below pump, It was under warrany tho, look very close at tank when you get it off



67066

I am going to make sure to acquire new hoses and o-ring. While I have it apart I see no reason not to do this and be on the safe side.
I certainly will check the tank for any cracks also. It surely has helped me look past what I originally thought was the problem. Thanks for all of the solution ideas!!!!

So far so good. I have the new hoses and 0-ring installed and it is dry so far. Thanks for the help guys. Now I cannot wait to get on the road.

Nice! Thank you for the update!