Fuel leak '04 R1150RT

[RT Pilot]

This morning I fired up the RT for an early morning recon around the county; while donning my riding gear I noticed a puddle forming under the cat converter. As the bike idled I stuck my head underneath and observed a pretty significant stream of fuel running down my rear shock assembly and onto the cat converter. . . THE CAT CONVERTER???!!!! I scrambled to my feet and quickly shutdown before flames erupted. I attempted to track the source of the fuel, but wasn't able to with the tupperware on. I fired the bike back up again and NO FUEL DRIPS this time. I drove about 5 miles around my neighborhood and came back--dry as a bone. Now I'm wondering why it leaked in the first place. . .why it doesn't leak now, and where it's coming from that it would soak the REAR shock assembly.

 

I'm planning on going to Maine later this week and will be going to places that aren't the end of the earth, but you can see it from there! In other words, I need to find the source of this leak and fix it before I go. . .does anyone have any idea what could cause this? I'll be taking the tupperware off this afternoon for a look-see and I'll report back if I notice any "smoking guns" (pardon the pun). I'll be closely inspecting the fuel line quick disconnects for seepage, as well as the connectors for the cannister and overflow vent, as well as anything else you guys suggest. By the way, the tank wasn't over-filled--it's a little less than half full right now.

 

Rob

[silverhornet]

fuel pressure regulator.

[RT Pilot]

Thanks for the suggestion---I'll check this afternoon.

[Bruce C]

I'll put my money on a cracked fuel quick disconnect. Clean all the fuel off any painted surface RIGHT NOW!!!

[Lucas2Bosch]

With it running down my rear shock assembly, I take that it would not be a full tank, and blowing out the vent tubes down the right of the cat. Cracked fuel quick disconnect, first thing I would check too.

[RT Pilot]

I wish I could report something significant. I took off the tupperware and looked everything over hard. I found where the fuel was running onto the right side of the rear fork and down where the bottom of the shock attaches. The only possible fuel source (that I see) above that is the cannister. I cleaned the hoses running into / out of the cannister, and gave them a good visual inspection--no cracks or leaks are visible. I also inspected the quick disconnects and they were dry with no evidence of any leakage around them (I didn't disconnect them again). I cleaned the rear fork and shock area where the fuel had dripped this morning and started her up and let it idle, just as I'd done this morning--NOTHING--no leaks evident around the cannister, the quick disconnects or anywhere else. NOTE: I should have noted earlier that the bike hadn't been started for over a week prior to this morning, so maybe there was some kind of build-up in the vapor cannister? I dunno. . .

 

So, what I'm saying is this may have to remain a mystery until it happens again. I've decided that I'll still make my trip and hope it doesn't happen on the road somewhere. If it does, I'm familiar enough with the system that I can probably fix it enough to get me going (as long as a fire department isn't involved). Other than this little quirk, this bike has never run better (25,000+ miles) I'm still open to suggestions if anyone has any other ideas. . .Thanks in advance! Now I'm going for a road test. . .

 

Rob

[RT Pilot]

I just put on 30+ miles (mix of highway and city). Still no evidence of fuel leaks anywhere--WTF? I think I'll have a beer and reflect on this awhile. . .

[DrPaul]

Had you filled the tank after the last ride before you noted the problem? If so, you might have overfilled it a bit, enough to flood the canister. Just a thought.

[RT Pilot]

Thanks for the suggestion Paul. . .no, I haven't added fuel for two weeks. When I started for the first time this morning it was just a little less than 1/2 full. After riding it this afternoon, it's down to about 1/4 full. I also thought it was the overflow vent initially, but all three of those tubes extend below the frame--there's no way (even after a few beers) that I can believe that gas is somehow running uphill to the rear fork.

[Stan Walker]

There have been a few cases of the vent hoses inside the tank cracking and allowing fuel to leak. Not too common and not likely to come and go.

 

More likely is that one of the original fuel line clamps is loose. They can be tightened with the right type of tool or replaced with screw type fuel injection clamps. For some reason leaks from these are often intermittant. Leak one day, then go several days without causing any problem. Almost as if the rubber in the fuel lines swells a bit under pressure, and shrinks back when not used.

 

see example nipper tool

 

Stan

[RT Pilot]

Thanks for the input Stan. . .as far as the hoses in the tank. . I just replaced my fuel filter a few months ago and that project went without incident (except I mixed up the two hoses in the tank and had to take everything apart to make it right again). For what it's worth, the hoses looked to be in fine shape when I had the tank innards out of it. I'd agree with you about the fuel line clamps, but I'm at a loss to explain why the fuel is seeping near the REAR of the bike--I'm not aware of any fuel lines (under pressure) back there. The only hoses that could carry fuel are the vent tubes to the cannister or the overflow, unless I'm overlooking something.

 

 

Rob

[RT Pilot]

OK. . here's a thought (not quite booze-addled yet). In my quest to find the elusive petrol leak I did notice a vent tube coming from the front of the bike (on the left side); just ahead of and above the 12V outlets there's a "fuel tank breather valve" (BMW #13901465030). The hose comes out of this valve and crosses directly to the right side of the bike (behind the fuse box). I don't know much about what this does, but I'm assuming it's controlled by the Motronic gizmo and only opens to vent the tank when it's told to. My theory is that because the bike hadn't been started recently, there was a build-up of gases in the tank that was sensed by the Motronic and it triggered this valve to open on the first start of the day. In addition to the gases being vented, I'm wondering if some fuel was dumped overboard along with the gases and that in my subsequent tests the Motronic didn't activate it for some reason. NOTE: I did NOT examine that vent tube closely for signs of leakage because the problem seemed to be on the right side of the bike.

 

Does anyone know what triggers that breather valve? Does my theory make any sense?

 

Rob

[awagnon]

Does anyone know what triggers that breather valve? Does my theory make any sense?

 

I may be wrong, but I thought the valve open when the engine was at cruising speed. That way, the extra gas, air, or fuel vapor entering the vacuum port of the throttle bodies won't have as much effect on the synchronization. The valve closes at idle. Someone please correct me if I'm wrong.

[MattP]

More likely is that one of the original fuel line clamps is loose. They can be tightened with the right type of tool or replaced with screw type fuel injection clamps. For some reason leaks from these are often intermittant. Leak one day, then go several days without causing any problem. Almost as if the rubber in the fuel lines swells a bit under pressure, and shrinks back when not used.

 

see example nipper tool

 

Stan

 

+1 I had the same symptoms, and it was one of the crimp-on clamps aft of the QDs, where the short rubber hose meets the plastic lines that 90 and go through the front of the air box. Cut them off with a pair of side cutters, replaced the rubber fuel lines, and used new FI-rated clamps. The only thing I've ever fixed on this bike that cost me less than $4.

[Ken H.]

Does anyone know what triggers that breather valve? Does my theory make any sense?

 

I may be wrong, but I thought the valve open when the engine was at cruising speed. That way, the extra gas, air, or fuel vapor entering the vacuum port of the throttle bodies won't have as much effect on the synchronization. The valve closes at idle. Someone please correct me if I'm wrong.

It's the purge valve to purge the charcoal fuel vapor recovery canister. And yes, it normally only opens at 'cruise'. Presuming the fuel vapor recovery system on this bike is still stock (do we know that to be true?) it would be difficult for fuel to come out the air input hose for the purge valve. The whole entire vapor system would have to be full of fuel. The OP would have noticed this. But at any rate a quick pull off of the vent lines from the tank will reveal if there is any fuel in them or not. If not, anything (vent) downstream, including the purge valve, can be eliminated as a source.

 

But back to the original leak symptoms, given the location I'm still inclined to suspect the fuel pressure manifold. I'd do a lot of "wiggle" test, with the key on, so the system is pressurized. Especially tug and pull on the hard lines where they disappear to in front of the air box.

[RT Pilot]

Thanks for the ideas Ken. . .I probably won't have the tupperware off before my trip unless I see the problem manifest itself again (I'll be riding to work as much as possible this week). When I do my next service I'll take your suggestion and start pulling on the fuel lines with the key on. Regarding the fuel pressure manifold--is that buried under the airbox? It isn't visible with just the tupperware off, is it? Another question. . if it was the fuel pressure manifold, why wouldn't the leak be consistent? BTW. . I've owned the bike since new and everything is still stock.

 

Rob

[Ken H.]

The fuel pressure manifold, and associated hard lines, it's all one piece, is actually located in front of the air box. It is a PITA to get to as the air box has to come out.

 

One might think a high pressure leak couldn't be intermittent, but history would prove one wrong!

[DavidEBSmith]

I thought my bike wasn't running right on the way to spring Torrey, but I couldn't track anything down. Then when I was riding around Minnesota in the MN1K in May, I thought I smelled gas once or twice, but didn't notice any leaks. Then one day riding around here I really smelled gas, and I found fuel pouring onto the cat. That was from the cracked fuel regulator manifold. When I got it off, I found that it had cracked right under the rubber grommet where it goes into the airbox, so it was mostly holding the fuel in, or at least would have until the line completely broke in two.

 

But other than the gasoline smell and the vague feeling that it wasn't running right, I couldn't find anything until I took the tupperware off (on the side of the road) and started the bike and saw fuel pouring down the left side and onto the cat.

 

And yes, the fuel regulator is a PITA to get to. You don't actually have to remove the airbox (the regulator sits on top of it in a little recess), but almost. It took me 6 hours to get to it, and 4 hours to get the bike back together.

[dave_jo]

Any more thoughts from anyone on this? MY '02 1150 RT has shown a few drops of gas a couple times. This morning, gas was dripping fast enough to form a puddle 12" in diameter in about 20-30 seconds. I shut it down and didn't ride it to work.

This afternoon I pulled the right tupperware and nothing, not a drip anywhere?

Think I should replace the hose clamps?

Thanks for any further help.

[RT Pilot]

Since I don't have time to mess with it before my trip, I'm going to take my chances and just keep a watchful eye on it (my insurance is recently paid up anyway). I'll be doing my fall service when I get back, and I'll try to get to the root of this and post some pics if possible.

 

P.S. If you're going to be traveling toward Maine this weekend and you see a black RT pass you that appears to be on fire--don't worry, it's just the (undocumented) factory raw-fuel after-burner option--It'll burn out eventually

[awagnon]

This afternoon I pulled the right tupperware and nothing, not a drip anywhere?

 

I would guess a clamp or a cracked quick disconnect that only leaks when the system is under pressure. Leave the tupperware off and turn on the key with the bike in neutral which will pressurize the fuel injection. You should find the leak. Shouldn't even need to start the bike.

[dave_jo]

I pulled the right tupperware and powered up the bike and looked for leaks. Nothing. Started it and looked for leaks. Nothing, not a drop. Took it for a ride without the tupperware and repeatedly stopped and checked for any sign of fuel leaking. Nothing, not even a hint of gas smell...

 

I inspected the quick disconnects. They seem fine. There was evidence of fuel washing the area near the rear end of the QDs where the fuel hose slips over the plastic tubing. I added another hose clamp to those connections (there was plenty of tubing inside the hose to clamp to).

 

I'll keep my fingers crossed that that is where it was leaking. Very bizzare that it would leak intermittently.

[dave_jo]

 

I inspected the quick disconnects. They seem fine. There was evidence of fuel washing the area near the rear end of the QDs where the fuel hose slips over the plastic tubing. I added another hose clamp to those connections (there was plenty of tubing inside the hose to clamp to).

 

 

Been over a week since adding the clamps. Everytime I've started or stopped the bike I have looked for fuel and sniffed for fumes. Nothing.

I think the second clamps worked.

[awagnon]

I think the second clamps worked.

 

Good work...!!

[RT Pilot]

I just got back from Maine. . .I put over 1700 miles on last week Anyway, during the trip, I rode the bike every day--nary a drop of fuel or any fuel odors whatsoever. So, did my bike fix itself? Unlikely, although BMW should offer that as an option.

 

Because I had several hours on the highway (10 hrs. each way to be exact) to contemplate these things, it occurred to me that at the time I noticed the leak, I was about midway through a treatment with Techron fuel system / engine cleaner. I'm wondering if the Techron somehow affected some sealing rings at some point in the fuel system, and then when I went on the trip (no Techron), the rings returned to normal size and sealed up again. . .I dunno, but if the others that have had this issue were using Techron, let me know. I'll still be doing my fall maintenance soon and will definately check that fuel manifold for cracks. If I find anything unusual, I'll post pics.