Fuel tank overflow problem (95 R1100R)

[jackyd]

I recently purchased a 1995 R1100R with 18k miles. I immediately had problems with fuel light (staying on when full, not coming on when empty, etc) The BMW mechanice diagnosed fuel light as fuel tank having a "vacuum problem" (diagnosed by opening fuel tank and feeling the vacuum suction with a "swoosh sound"). We disconnected vapor line that runs from fuel tank to charcoal cannister to correct the vacuum problem. This did correct fuel light problem but soon after the fuel overflow line would drip when tank was over 3/4 full. Drip is slow and slight but but fumes are noticeable in garage.
It seems the disconnect of "vapor line" and the dripping of the overflow lines may be related..??

Any suggestions would be apprciated

Jack

[j-budimlya]

that the tank was more than "3/4 full" ...

If this was determined by the guage, the guage sender may be malfunctioning...

the tank cannot leak gas when its 3/4 full...it would have to run up hill..

this all assumes that the correct hoses are on the correct connections...

I wonder if the carbon canister is "dripping"...

have you removed the carbon canister....

in cold weather, it can probably condense and leak some gas if it was "full'; before you disconnected it....probably one bolt to take off...

I have removed the canister from my 1995 R1100R many moons ago...and no gas ever leaks from the bike....

[rgvilla]

the fuel tank on your bike is constantly pressurized so I would say that disconnecting a line would cause the drip, except that it isn't coming from the disconnected line is it? I would suggest changing all your fuel lines and hose clamps as these can wear and cause leakage. This recently happened on my 99 R1100R and replacing the clamps fixed the problem. I also changed the hoses just to error on the side of caution. you might as Paul Glaves, he's a great wrench.

[jackyd]

I removed seat and side panel. The leak is definitely coming from the "overflow tube" from the gas tank. I cannot tell where the tube enters the tank (I had hoped to resolve without removing tank)
I removed charcoal cannister and checked hoses leading into canister. No obvious blockage.
I reconnected the tube running from fuel tank to cannister to see if this stops leak.
The most likely solution is as stated; repalce cannister and all tubes
Thanks for help

Jack

[cjack]

I recently purchased a 1995 R1100R with 18k miles. I immediately had problems with fuel light (staying on when full, not coming on when empty, etc) The BMW mechanice diagnosed fuel light as fuel tank having a "vacuum problem" (diagnosed by opening fuel tank and feeling the vacuum suction with a "swoosh sound"). We disconnected vapor line that runs from fuel tank to charcoal cannister to correct the vacuum problem. This did correct fuel light problem but soon after the fuel overflow line would drip when tank was over 3/4 full. Drip is slow and slight but but fumes are noticeable in garage.
It seems the disconnect of "vapor line" and the dripping of the overflow lines may be related..??

Any suggestions would be apprciated

Jack
It seems like not a cannister problem, except that when a cannister fills with gas as this one probably did, the cannister sometimes is ruined inside by the carbon granules becomming unlodged. Since the overflow did not leak until the tank was 3/4 full, then I would suspect a crack or open somewhere in the overflow hose which goes from the top of the tank to the near bottom side of the tank. That would also account for the vacuum since the overflow was full of gas, etc. How this is connected to the fuel light problem is unknown, unless the hose was loose inside and interfering with the float assembly. That may make the most sense. Is the vacuum still there? I would think it would be if this were the problem.
This may not be the problem, and I don't mean to put you into the work of taking off the tank, but thought it worthy of mention if your problems persist.

The overflow-vent hose enters the tank on the right side along with the gas line hoses and drip hose from the filler area, wiring, and float assembly...all attached to a big round plate that is secured to the underneath side of the tank.

[j-budimlya]

the fuel tank on your bike is constantly pressurized so I would say that disconnecting a line would cause the drip, except that it isn't coming from the disconnected line is it? I would suggest changing all your fuel lines and hose clamps as these can wear and cause leakage. This recently happened on my 99 R1100R and replacing the clamps fixed the problem. I also changed the hoses just to error on the side of caution. you might as Paul Glaves, he's a great wrench.

the tank itself is never pressurized.....only the line form the pump through the filter and to the injectors....it is then returned to the tank...and the pressure is released....the tank is not pressurized.....ever....it is in fact vented to the atmosphere to vent off any pressure buildup....this normally occurs "through" the carbon canister....and the carbon absorbs the gas vapors.....hence the pollution control purpose.....if the carbon cannister is removed properly, and the the plumbing hooked up correctly....the tank will just be vented to the atmosphere.....if its not removed correctly, it probably can build up some pressure......and maybe cause a leak....there is a valve in the plumbing that applies vacuum to the cannister during initial engine startup.....if this valve is left in the vent line circuit...it could cause a problem....

[PGlaves]

The "overflow" tube is actually two small metal pipes and two hose segments. The top pipe is brazed/welded to the insert at the top of the tank immediately below the filler cap. A hose connects to this little tube up at the top and runs internal to the tank to the second short pipe segment. This segment goes through the pump/filter mount plate. Then the hose you see runs from the exterior end of this stub pipe down to the vicinity of the footpeg.

There is a crimp-on Otiker clamp (or maybe a screw-on by now) which fastens the bottom of the hose to the stub pipe through the plate - buried in fuel inside the tank. BMW supplies hose which is too short inside the tank. Every time the filter is changed you wrestle with these little hoses to get the pump and filter out for filter change. The clamps loosen and fuel seeps into the hose inside the tank and runs out the hose.

On our Oilheads I have replaced the hoses inside the tank with replacements about 4" longer than stock. This provides maneuvering room without stressing the hose and clamped connection.

In any event, you need to drain fuel, remove the tank, remove the pump plate and resecure both the vent hose and the drain hose to the stub pipes inside the tank with good clamps. Check the hoses for dryness or cracking or other deterioration while you are in there. The source of the leak is into the hose inside the tank, either at the clamp (most likely) or through a defect in the hose.

[j-budimlya]

Good place to start looking....

BTW, get a new gasket for the plate you are about to remove...it will take a few days for the old one to shrink back to original size to make installation possible....and it may be too old to work right...

[AntonLargiader]

I'd figure on replacing the two vent hoses inside the tank. If the bike has sat with old fuel in it for a while, the rubber will decay.

16 11 1 342 049 is one meter of the hose, 16 11 2 313 574 are the clamps you will need. Also make sure the metal tubes are clear where the lines pass through the filter plate. If you still have the canister you'll need to keep the lines organized so that the vent goes to the canister and the drain goes to the ground.

[rgvilla]

I stand corrected, I misquoted my Clymer (p307) "Depressurizing the fuel system" which states "The fuel system is under pressure at all times, even when the engine is not operating." not fuel tank, my mistake.

[jackyd]

Thanks to all for providing ideas on how to correct the leaking overflow pipe.
It became obvious problem was inside fuel tank and I did not have time this month so the bike went to Morton's in Fredericksburg Va.
Problem was wornout rubber tubing and clamps inside tank connecting to vent lines. The carbon cannister was shot as well but the problems were not related.
1. Float was not working due to "vacuum" forming in tank, caused by bad cannister which prevented normal ventilation.
2. Gas overflow problem began when tube to carbon cannister tube was disconnected in order to correct problem #1 (which it did.. disconnecting tube corrected vacuum and fill light began to function normally). Assumption that problem # 2 was related to problem #1 was wrong.. Tube internal to fuel tank had worn out (as a few members had predicted) which daused leakage.

Both problems now resolved

Jack