engine filling up with gas

john S. · #1 (**permalink**) 09-08-2008, 07:19 AM

My 916 went dead on the highway. Later I thought it was a disconnected fuel line in the tank. I fixed that but noticed something really weird, gas dripping from the lower exhaust pipe when I try and start it. Eventually the bike wouldn't turn over and the site glass showed no level of oil, it was like I put 8 quarts in it. I suspected that fuel was getting into the motor somehow and confirmed that when I opened the drain plug. An ugly mix of gas and oil and lots of it came out. Since I thought it might have been that fuel line, I put fresh oil in the bike with a new oil filter and tried to start it up. Again, gas was dripping from both lower exhaust pipes so I immediately shut the engine down. This time the bike turned over due to the fact the engine wasn't filled with gas. I disconnected the fuel lines and connector and hit the starter switch and the bike actually started. It went with what fuel was in the lines which was for 4 or 5 seconds, but I still noticed gas dripping from the seams of the lower exhaust pipes. Both pipes. I removed the horizontal exhaust pipe and you guessed it, it was full of gas! I suspect the vertical cylinder is full too because it was dripping gas as well. BTW, no signs of gas trail back to the connectors or the tank that I could detect.

What the hell is going on? I can only guess a throttle body or injector is gushing gas into the cylinders. But both cylinders, or is it one and it just overflows into the other?

Has anyone had this oddball situation? I just ruined 8 fresh quarts of synthetic and two oil filters.

ccolwell · #2 (**permalink**) 09-08-2008, 10:55 AM

Much the same thing here, but I caught the leak before it filled the cylinders. Based on conversations with a friend who used to be a service manager at a local big four dealer, I believe current gas ethanol formulations leak past the material used for seals and gas lines on Ducs. Keep your fuel tap closed when not in use. I'll be changing all the fuel lines this week on mine.

Ducman851 · #3 (**permalink**) 09-08-2008, 02:02 PM

No fuel tap on the 916.

Sounds as though you have a injector stuck open.

**departmentofsuspension** · #4 (**permalink**) 09-08-2008, 05:26 PM

The first thing you want to do is check the pressure that the pump/regulator is set at. It will probably be normal but you gotta check.

If it still does it remove the injectors, run 12v to the two poles in the part where the harness plugs in which will pop the injector wide open and then clean it out with carb clean. You can check to see if it worked by putting any kind of hose you can stretch over the injector inlet and fill it with fuel. If the injector doesn’t leak you are good to go. If you want to be doubly sure you can blow as hard as you can into the hose which will pressurize the fuel going into the injector. And if you want to get crazy anal you can set your compressor at 45psi and use a air gun to pressurize the fuel in the hose and see if the injector leaks then.

If none of that solves the problem you may have a ECU issue that is causing the injectors to hang open.

john S. · #5 (**permalink**) 09-13-2008, 05:34 AM

Thanks,

I suspected something to do with the injector. I'll copy your response and take it with me when I drop the bike off at Nichols. Thanks Duc851 as well.

motodave · #6 (**permalink**) 09-13-2008, 11:42 AM

Did you or somebody recently replace the "chip" in the computer? I had this happen to me when installing the chip in BACKWARDS!!! It flooded the motor something fierce and fuel dripping out of the front exhaust pipe.

john S. · #7 (**permalink**) 09-13-2008, 07:51 PM

Quote:

Originally Posted by motodave

Did you or somebody recently replace the "chip" in the computer? I had this happen to me when installing the chip in BACKWARDS!!! It flooded the motor something fierce and fuel dripping out of the front exhaust pipe.

I did take the lid off my P8 to look at the chip connection. I put the chip in 3 years ago when I bought a 1/2 system from Jason. This time I started to remove the circuit board from the top and then realized I was doing it the wrong way. However, I could see underneath and recognize the chip was in place. I hope I didn't mess things up more by prying on the circuit board. It could still be the ECU somewhere I suppose. Anything is possible at this point.

john S. · #8 (**permalink**) 10-06-2008, 02:48 AM

Sure enough, the problem was related to some internal P8 computer parts being out of alignment. Nichols actually identified the problem within an hour and called me back to pick up the bike. Fortunately I was still in the area with my trailer and by them going after it quickly saved me $80 in gas and time since I live 2 1/2 hours driving time away.

Thanks Nichols, you saved my ass again.

Shazaam! · #9 (**permalink**) 10-06-2008, 03:29 PM

The engine management system uses a throttle position sensor to monitor throttle input so the computer can supply additional fuel to the engine when you turn the throttle grip. This sensor's resistance changes as you vary throttle opening from full-closed to full-open much like the volume control knob works on a radio.

An open TPS circuit gives a fail-safe closed throttle signal but a short circuit in the wiring or connector to the ECU will give a wide-open signal and result in the condition you describe.