Gas Tank Sucks

[BeemerBerg]

When riding a long day, burning through a tank of gas, I notice that when I go to fill it up, when I open the gas cap, there is a giant sucking sound from the vacuum created in the tank. Is this normal? I thought the tank was vented to compensate for the gas being used up.

Something I should worry about? Bike runs great: 55 mpg avg. No issues.

[dirtrider]

Evening BeemerBerg

 

Not normal-- you have a plugged or mis-connected emission evap system.

 

If you don't repair it or eliminate it the vacuum in the tank will suck your fuel tank sides in & can damage internals.

 

You are in the camhead section here so if a different bike let us know. (the old oilheads usually crush the fuel gauge sender)

 

If you tell us exactly what bike you are working with we can probably advise a bit better about checking the tank vent for improper routing or being pinched or plugged.

[BeemerBerg]

Bike is 2010 R1200 Rt (camhead)

 

Gas tank 'imploding'. Yikes!

 

The vacuum for the evaporative canister comes off the left cylinder, and the vacuum hoses seem to be hooked up properly. But something has to replace to volume being consumed while riding.

 

Could the canister be plugged up? If the gas tank is 'overfilled' during fueling, could that back up into the canister? Or maybe the gas cap not venting?

 

In previous models (oilheads) a Canester-ectomy was a common surgical procedure. Should this be considered for camheads?

[Dave_in_TX]

Bike is 2010 R1200 Rt (camhead)

 

Gas tank 'imploding'. Yikes!

 

The vacuum for the evaporative canister comes off the left cylinder, and the vacuum hoses seem to be hooked up properly. But something has to replace to volume being consumed while riding.

 

Could the canister be plugged up? If the gas tank is 'overfilled' during fueling, could that back up into the canister? Or maybe the gas cap not venting?

 

In previous models (oilheads) a Canester-ectomy was a common surgical procedure. Should this be considered for camheads?

 

On your canhead, there is no gas cap vent as that would defeat the purpose of the canister. Venting is through the canister.

[dirtrider]

Morning BeemerBerg]

 

 

The vacuum for the evaporative canister comes off the left cylinder, and the vacuum hoses seem to be hooked up properly. But something has to replace the volume being consumed while riding. ---The vacuum hook up is to PURGE the evap cansister. There is also a drain/vent hose coming off the evap canister to allow the fuel tank to vent. (should run back then down the L/H side & exit around rear of engine).

 

Could the canister be plugged up? ---Yes, but you could also have a plugged vent hose between fuel tank & evap can, or a pinched hose, or someone might have plugged a hose when removing the fuel tank & forgot to unplug it. OR possibly the vent hose going to the rear has the end plugged with dirt or a mud dobber bee. (check them all befor replacing or removing the evap can)

 

If the gas tank is 'overfilled' during fueling, could that back up into the canister? ---Yes, that can turn the charcoal in the evap can to a mushy mess. Not as likely to happen as on the 1100/1150 bikes but could happen.

 

Or maybe the gas cap not venting?---Your gas cap in not vented (this is required for the evap system to store hydrocarbons & recover/burn them)

 

In previous models (oilheads) a Canester-ectomy was a common surgical procedure. Should this be considered for camheads? --- Only IF a plugged evap can is the problem & BMW won't warranty it under extended emission (evap system) warranty.

 

First thing-- try to figure out WHERE the fuel tank vent system is plugged. On the 05-09 BMW 1200RT there is a hose running from about the front center of fuel tank to the R/H front mounted evap can (not sure if your 10 is exactly the same).

 

If your 10 is the same then there should be a plastic connector (push in type) about half way between the tank & the evap can. If you can find this connector you can (with great difficulty) pull the hose apart. Then use a longer (separate) hose & hook it first the rear hose (one going to the tank) then open the fuel tank cap & blow air into that hose. If air flows into the tank & out of the open fuel cap easily then that part of the vent system is open.

 

If you CAN'T blow air into the tank through the vent hose then suspect that hose is pinched off, plugged, OR the roll-over safety valve inside the tank is stuck closed.

 

If you can blow air into the tank & have it come out of the open fuel cap then switch your added hose to the hook to the hose going forward & blow air into that. If you can't then something in the evap can is plugged or a hose going to or coming from it is plugged.

 

For the next tests you will have to remove the Tupperware & access the evap can.

 

Once you access the evap can then disconnect the vent/drain hose running to the rear then repeat blowing air into the hose going to the tank. If you can NOW blow air into the evap can & have it come out then look for a pinched or plugged vent/drain hoses going to the rear & L/H side of bike & exiting about mid bike.

 

If you still can't blow any air through the evap can then it is probably plugged so would need to be replaced or removed.

 

My personal take is: the evap system on the BMW 1200 bikes is pretty bullet proof & is one the most effective raw hydrocarbon removal emission devices so I try not to remove them UNLESS ABSOLUTELY NECESSARY. The evap can is also a GREAT device to keep moisture from entering the fuel tank & mixing with the alachaol in the fuel causing other issues during storage & long term bike sitting.

 

If you do find that your evap can is plugged then contact BMW to see what their emission warranty covers--in a lot of cases the emission warranty (by state or Federal mandate) is longer than the bike's standard mechanical warranty period.

 

 

 

[BeemerBerg]

DR--

Thanks so much for your detailed explanation!!

 

I took off the upper & lower tupperware from the right side of the bike. The evap canister is right there--front right. It is the same as on the earlier hexheads.

 

There are two hoses on the top of the canister: the one towards the front of the bike that goes to the top of the gas tank. I disconnected and did the "Blow test". It was fine. The rear hose goes right up to a valve thingy above the canister. Then There is a hose on the other side of the top front of the canister that goes to the left throttle body (started engine up, and it sucked as it should).

 

Then there is a hose coming out of the BOTTOM front of the canister, that routes along the frame, and exits down by the right footpeg. When I disconnected this hose from the canister nipple, a bunch of little 'carbon pellets' came tumbling out of the hose. The suck/blow test proved that the hose was totally plugged up!! A little work cleared out all the pellets.

 

It looks like the evap canister puked its carbon stuff into this exit hose, maybe causing my 'gas tank sucking issue'??

Would this mean that the canister is kaput?

 

Other than hastening global warming, is there any reason why I couldn't just simply bypass that whole nonsense, and route the gas tank hose to the (now cleared) waste hose (venting directly to atmosphere)? [Canisterectomy]

 

Thanks for your assistance!!

[dirtrider]

Morning BeemerBerg

 

 

 

Then there is a hose coming out of the BOTTOM front of the canister, that routes along the frame, and exits down by the right footpeg. When I disconnected this hose from the canister nipple, a bunch of little 'carbon pellets' came tumbling out of the hose. The suck/blow test proved that the hose was totally plugged up!! A little work cleared out all the pellets.---This is/was more than likely your tank sucking problem.

 

It looks like the evap canister puked its carbon stuff into this exit hose, maybe causing my 'gas tank sucking issue'??

Would this mean that the canister is kaput? ---Yes, your evap can if definitely bad.

 

 

Other than hastening global warming, is there any reason why I couldn't just simply bypass that whole nonsense, and route the gas tank hose to the (now cleared) waste hose (venting directly to atmosphere)? [Canisterectomy]---Yes, you could do that & it would/should stop the fuel tank sucking problem. That does make your bike illegal (but no-one ever seems to check) & makes your bike a raw hydrocarbon polluter. You might call your BMW dealer or BMW itself & see what their fuel system emission system warranty covers & for how long. (in automobiles the fuel system evap emission warranty period is quite long)

 

[BeemerBerg]

Check the 'source of all wisdom & knowledge' [internet], it looks like the evaporative canisters should have a foam screen that should keep the little charcoal pellets from exiting any of the nipple connections. Probably failed on the bottom side, allowing the little devils to clog up the tube.

 

Luckily, our friends at Beemer Boneyard have one for $20. Order up. Assuming that these things don't fail often, a used one ("low mileage"} should be as good as a $$$$ new one.

 

Breathe easy, fellow riders, my RT will be environmentally correct.

Thanks for your patient advice.

[BeemerBerg]

This reminds me of a cartoon I saw long ago: Couple looking at new model non-polluting car. Has a giant balloon atop, connected by hose to tail pipe. Car Salesman to couple: "Latest technology. When it's full, you just throw it away".

 

You will find my old canister in the local landfill. What have we gained?

[Mike]

Maybe it's because I'm such a rube, but I am continually amazed and the knowledge and helpfulness of our members. Thanks, dirtRider and BeemerBerg, for jumping in to help out!