Fuel vent valve fail?

[emseedee]

I'm still trying to get to the bottom of the problem where my 13 plate C650GT sometimes stops when it should be idling - particularly just after a fast run. I was going through all the options on Motoscan, which connects to the ECU. In the engine / actuators category there's an option to switch on and off the fuel vent valve, and I can't hear anything happening when I exercise the valve. I'm wondering if this is normal, or if I should be able to hear the valve operating. A valve that isn't opening when it should could potentially cause fuel starvation and stalling.

 

[Ceesie76]

On my 2007 F800ST, when I bought it in April, I ran a Motoscan on it and there was a fault code for the fuel vent valve. So, I would think on the C650GT a code would be set as well, meaning that if yours does not have one set, the valve is probably ok. I don't know if they make an audible sound when opening/closing but this would be my guess.
I got a new valve on Amazon, cost was around $85 as I recall, so you can replace yours just to rule it out as a possibility, not that expensive.

Have you checked the small idle air hoses? One of the two on my 2016 Sport was torn, and symptoms can be poor idling, stalling etc.

 

[mjnorris]

I'm still trying to get to the bottom of the problem where my 13 plate C650GT sometimes stops when it should be idling - particularly just after a fast run. I was going through all the options on Motoscan, which connects to the ECU. In the engine / actuators category there's an option to switch on and off the fuel vent valve, and I can't hear anything happening when I exercise the valve. I'm wondering if this is normal, or if I should be able to hear the valve operating. A valve that isn't opening when it should could potentially cause fuel starvation and stalling.

I’ve posted on one of the causes before. It could be one or both of the vacuum lines going to the idle control mechanism. I had this problem and another member posted about his troubles and like his mine was caused by the vacuum lines. This may not be your cause and the only way to be sure is to remove enough tupperware to visually inspect these lines. Mine looked like a cat with steel claws had slashed them. The lines are cheap for BMW but it’s 2-3 hours of labor.

 

[emseedee]

Yes, been down all those rabbit holes. Had the hoses off and they looked fine. The idle control valve seems good, changed the plugs and coils which helped a bit, but there’s still just the odd time when the engine stops after coming to a halt. Much less frequent now though, more of annoyance than anything, but I’d still like to get to the bottom of it.

 

[Ceesie76]

How do you know the idle control valve is good? You wrote that "it seems good" but have you tested it? And, before you wrote about the fuel vent valve, did you test that (or is it the same valve)?

 

[emseedee]

I can exercise the idle control valve with the Motoscan app. If I do this while it's removed from the air box but still connected to the wiring harness. I can see the piston movement. I can also hear it moving when it's installed. I'm not sure where the fuel vent valve is. I just noticed that when I try and exercise it with the app I can't hear anything happening.