Fuel Tank Pressure Build-up

[NCD]

Note that there are 2 check valves back at the R corner of the tank under the trim panel.

#1 is the large white unit bolted into the tank where the vent hose attaches. That is the weighted tip-over shutoff valve that you can hear knocking around when you rock the bike back and forth.

#2 is the inline check valve with the 2 way properties being discussed. It is a 1" long silver cylinder stuck inline to the vent hose about 6-8" behind #1. It is ziptied to the frame before the hose does the 180 and heads back down toward the canister.

Inside that little cylinder is a green ceramic check ball. It is porous, with microscopic holes in it.

Those pores get plugged up with the aluminum corrosion dust from inside the cylinder and cause your tank to hold pressure beyond the 5psi expected.

Solution? The cylinder splits into 2 pieces. Open it, toss the check ball in the trash, and reassemble.

Mine has been like this all HOT summer with no ill effects. Canister still attached and working fine.

This permanently cures tank POSITIVE pressure, and lets you keep the canister to control the fumes in your attached garage.

The mighty Joel W. helped me with this diagnosis - - I'm just putting this info out there for the masses. He said BOTH valves can stick, so check them independently (suck/blow through them - it tastes like shit, so be prepared.) He did say that #2 is the usual culprit.

[itsatdm]

Thank you, I feel exonerated and informed at the same time. Good info, should be in a sticky.

[tempeturtle]

There seems to have been a plug in some line that caused the fuel pump to heat up and cause the pressure. At least that is what I am guessing from the fault code report. It shows good voltage put very low (almost zero PSI) fuel pressure from the fuel pump.

READ OUT BELOW FROM MY GS911

10168: Electric Fuel Pump System faulty
The fault is not present now.
This fault occured 4 times.
Logistic counter: 31
Symptom: No signal or value.
MIL set: No

Fault code history:

Electric Fuel Pump Voltage 12.62 V 12.25 V 12.62 V

Odometer 15952.6 miles 15952.6 miles 15957.6 miles

Engine Speed 3280.00 rpm 1160.00 rpm 1360.00 rpm

Measured Fuel Pressure 0.39 hPa 0.41 hPa 0.37 hPa

Throttle Valve Angle 29.30% 0.00% 0.00%


If you like to work on your own bike like me then this tool (GS911) is invaluable. The reports it provides look much better then this but I was not able to transfer it directly via text.

Does anyone else have the same or different interpretation of what caused this as I do?

Original symptoms: Bike stalled from a standstill or very slow movement; It would restart but got progressively worse until it would not; and finally after it would not restart I opened the gas lid and fuel came out like a guesser (a liter or more).

Any insights would be welcomed.

andy

[JRWooden]

Andy:

I'm not sure how I would interpret that ....

For example -- lets say the impeller wheel were spinning on the shaft of the fuel pump motor, or the bearings in the motor were going bad causing it to run slowly .... or say the input filter sock were clogged ....
would the reported fault not still be the same ...

i.e. good voltage to pump, but pump output was crap?

I'm just brainstorming with you here

[space]

Andy, did you ever figure this out?

I've been having the same symptoms on my HP2. Intermittent stalling and same error code on the GS911. My guess is a clogged fuel line upstream of the pump, probably due to debris in the tank or bad gas.

I'm about to take apart my fuel system and check, but I'm wondering how this turned out for you.


EDIT: yep, turns out I had a large wad of black gooey glop (technical term) backing up the screen of my pre-pump filter. I hope your problem was similarly easy to fix.

[tempeturtle]

Mine was also the little porous ball that got gummed up and thus creating a blockage. Have not had the problem since. Gas in the Phoenix area just seems bad, all of my bikes carbs (harley, and a couple of honda dirt bikes) get gummed up. I am now using sea foam and it helps.

Originally Posted by space

Andy, did you ever figure this out?

I've been having the same symptoms on my HP2. Intermittent stalling and same error code on the GS911. My guess is a clogged fuel line upstream of the pump, probably due to debris in the tank or bad gas.

I'm about to take apart my fuel system and check, but I'm wondering how this turned out for you.


EDIT: yep, turns out I had a large wad of black gooey glop (technical term) backing up the screen of my pre-pump filter. I hope your problem was similarly easy to fix.