Strange fuel issues with 2001 Monster 900

[Christian]

Hey folks,

I've got an EFI M900 that's behaving badly and I'm trying to resolve it.

About a week ago the battery started acting up and wouldn't charge properly. I managed to narrow this down to the regulator / rectifier. After sourcing a new one and swapping it out the bike actually started and seemed okay.

However, a short ride showed some more strangeness. Despite having a full tank of gas the low gas light came on. The bike seems to idle okay but riding it will cause a lot of sputtering and loss of power. I don't think it would make it very far if I tried to ride it outside of a parking lot.

I removed the fuel filler cap to take a peek inside and saw that one of the drain lines had torn a bit. I believe this spring is just to prevent line kinking, right?




Another cap shot - this line is suppose to sit right in the tank, I believe:




I didn't have any line handy so I put it all back together planning to pick up some parts to at least replace that line. Once I put the cap back on the fuel started coming up through the top of the bike. I have no idea why.

The tank wasn't so full that inserting the cap would cause it to overflow. Maybe the torn line caused some weird pressure differential?





At this point I have a new filter and some new fuel lines. I'm going to drain the tank out completely, replace the cap gaskets, filter, and hope for a loose connection somewhere around the pump to make it obvious. It's a bit tight in there, though. I'll also drain all the gas and refill to remove that from the equation.

Is there anything else I should be looking for? Am I on the right track here generally?

Would the torn drain line cause the fuel issues I'm seeing? Maybe the tank can't get enough pressure to let the fuel pump work?

I'm open to any thoughts and ideas. I'd love to get this thing running again.

Thanks in advance!

[Howie]

Definitely replace all lines and fuel filter first.  If you find any rubber particles or other yuk in the tank take care of that.  Then, if the bike is still problematic, take it from there.  Make sure you use fuel line that meets SAE 30R10 specifications.  Fuel light is a separate problem.  With enough fuel in the bike, at least a liter if the light is on, disconnect the connector on the bottom of the tank.  Turn key on.  Light off?  Bad sender.  Light still on?  dash/wiring problem.

[Christian]

Thanks, howie. Good tips there. I didn't think to disconnect the sending unit to see if the light resolved itself.

There was this trifecta of events that all coincidentally happened at the same time, so I thought the fuel light was related to the running issues.

My off the cuff guess was that the regulator fried the fuel pump, which is causing the running issues and might trigger the low fuel light.

I'm not looking at the bike right now, but are there two different connections for the fuel pump and sending unit? Would a pinched wire cause these issues as well?

Thanks again!

[Howie]

Again, filter and hoses first.  If they leak or suck air you will have running or possibly will not run problems.

[Christian]

Update to the thread:

I replaced the broken drain line and cleared out both drains.

Removed the fuel pump assembly and inspected it and replaced the fuel filter.

Drained the entire tank of gas and made sure to get every last drop.

I put a bit of dry gas in the tank along with a fresh batch of gas - about half a gallon or so - and re-assembled everything and she started up great.

A short test ride showed the fuel light to be fixed and all the hesitation and sputtering to be gone.

From what I can tell, the busted drain line and clogged drain lines resulted in some water in the tank. We've had some heavy rain the past few days. The regulator / rectifier threw me off but was unrelated.

Thanks again for the tips, howie!