Fuel Tank (non)Venting Issues

[browad]

A bit of history. 3000 miles in to my 6000 mile trip in August my canister died (I believe I was in Quebec), which caused my fuel sensor to crunch and stay at the 3/8 mark. I assumed that the canister died because around the same time when unscrewing the gas cap air would rush out.

After I got home (about 4000 miles after it happened and at my 32k service) I took the canister out and rerouted the throttle side vent line down and out and capped off the brake side line with a bolt. It did not seem to affect the venting, so I assumed that something else was going on and when I brought the bike in to a dealer they would be able to give me more info.

On Saturday I took the bike in to get the fuel sensor replaced under warranty with the venting issue still going on. The tech replaced the sensor (functioning fuel gauge at last!) but was unable to do anything about the venting because I had changed the system. Ok, I get that. But what he suggested I do (routing the vent line etc) I had already done, with no effect. I got the bike home while stopping to vent the tank and later keeping it slightly unscrewed so that my new fuel sensor would not re-crunch.

Back home I started playing with the two lines seeing if perhaps I capped the wrong line. Any variation I tried did not make a difference, the fuel tank still did not vent correctly. On the throttle side line you could feel a pulse of vacuum so it makes sense to leave that line open, but even with it capped there was still no difference.

My thoughts are the following:

1. For the throttle side vent hose I simply took off some excess hose from existing and ran it under the tupperware to under the right passenger peg. On looking at the BMW manual it seems perhaps I should not use the existing hose but need to take off the right side tupperware and grab it there. The canisterectomy faq on this site is not clear on this.

2. Run compressed air through the vent lines, perhaps there is a blockage farther up (leave this for last)

3. Take the fuel tank off and check for installation issues from the 24k service

That's about it. On the fuel system there are a limited amount of suspects, and I'm about tapped out.

Thanks for the help,

[zippy_gg]

I think option #2 might do the rick. Maybe your canister was not the problem to begin with, but a clogged hose was.

[browad]

Yeah, I was thinking this too. Usually not too happy with blowing compressed air through a hose unless the entire hose is unhooked.

However, I can feel the vacuum pulse through this hose. Would a partial blockage be enough?

On the plus side, it can only go back into the fuel tank, correct?

Cheers.

[sheldan2]

straight into the tank and into your fuel filter which could get blocked and you would then need to get it replaced.

[jzeiler]

If you are feeling the vacuum pulses - that is the line to the throttle bodies and it should be capped. The only other line back there is the one to the roll over valve and that should be open to the air to allow the tank to vent. You should be able to blow into that line and hear air at the gas cap opening. If you can't then it maybe pinched the last time you had the tank off.

[tvolk]

Had a similar issue after the dealer installed my new Ohlin shocks.

Turned out that they pinched one of the vent lines when reinstalling the fuel tank.

They fixed it--but what a hassle taking the bike back to the dealer!

Good luck. Evidently it is easy to do (pinch the vent line)

[browad]

Hunh. So I capped the wrong one. Had a 50/50 shot and still didn't get it. Figures. I'll play with them tonight. I have a feeling that a line is pinched from the fuel tank install. Update to follow.

[browad]

http://lh3.ggpht.com/ribbondarkness/SM8B1We-v3I/AAAAAAAAAOc/1fOS35agc5A/s800/IMG_0129.jpg

So...looky what I found. Problem fixed.

[jrlakin]

The picture isn't very clear. What was the problem???

[Steve_R]

Not sure what he's trying to show, but I bet he found a power cable connected incorrectly.

[jzeiler]

There is a pinched line right under the bolt next to the frame.

[browad]

There is a pinched line right under the bolt next to the frame.

Ding ding ding! Sorry about the crappy iPhone photo, but yes that is the vent line under the fuel tank right at the attachment point. Since I took the fuel tank off for my 24k service, that means I've had this problem for ~8k miles and not the 4k I said earlier. And it was my own fault.

So this has been added to my internal fuel tank removal checklist. And now my rear speakers aren't working (since before I took the stingray off ;-} ), so I'm problem solving that.

Thanks for the help.