Fuelpump and Gastank problem

[Red FZ6 Rocket]

Today I was completing the Dual H4 Headlight Mod w along with installing a K&N Air Filter. When I raised the gas tank the vent hoses let off a lot of built up pressure and rusty water or old fuel came out of the hoes, they had been kinked underneath the tank by the dealer or previous owner. I had always wondered why when I fueled up the gas cap let off pressure. Here is where problem comes in I get most of the front faring put back together and go to start the motor and fires up for split second and shuts off, I tried turning a little long and it would fire and die, fire and die. So I start looking for anything that be might disconnected but everything was hooked up right. When putting the gas tank down I pulled the vent hoses so they would not be kinked anymore. They had so much extra length I cut 2" off so they would just clear the center stand. The these vent hoses drop down by the rear brake pivot bolt. Well after search my service manual for an hour with no apparent cause for the stalling , no diagnostic code where being displayed. I decided to plug the vent hose from the gas tank with some bolts to see if the motor would get more fuel, and low and behold she came to life again. Took the bolts back out of the vent hoses and it fires and shut off. There back in and no trouble on a short ride around the block but I won't trust it until I know what's wrong.

So now I need help finding what was damaged by kinking the vent hose.
Any help or ideas would be greatly appreciated. Thanks Ken

[Fred]

I'd suggest tracing the hose that you're plugging and unplugging.

The tank vent hose and the rainwater drain hose should not be causing this problem, plugged or unplugged. So that leads me to believe that somehow the hoses are messed up, and one of those hoses is connected to somewhere other than the gas tank.

Raise up the tank again, trace the hoses and make sure that they both go to the tank and nowhere else. Best guess is that somebody "improved" the bike somehow.

Fred

[Red FZ6 Rocket]

Fred
I also had a hard time believing a drain hose could cause this problem but I'm positive both hoses go to the tank. I traced them about four times before yesterday's post. Plus when lowering the tank I had to pull them as the tank lowered into position. The only thing I can think of is some kind of fuel line pressure valve in the fuel pump design being damaged by the excessive pressure helping to push the fuel out of the tank and without that pressure it's not getting the right amount of fuel. I plan throughly check out the fuel pump schematic today looking for a pressure valve or a fuel regulator. I don't believe it was done intentionally, I bought this bike in May of 08 from a 75 year old man with 2002 miles on her. Now she has a little over 4k and the mods have begun.

Thanks for the response and your thoughts. Ken

[bd43]

I'm kind of wondering if the pump is no longer running. Are the wires to it look okay? They might have been pulled out when you lifted the tank. I was thinking you're no longer getting any pressure from the pump and when the lines are venting, you release what ever pressure builds up naturally within the tank. I'd check that out, make sure the pump is running. My 2 cents.

[Red FZ6 Rocket]

Hey BikerDude

Yes, I hear the fuel pump come on every time the main power and engine switch are powered.

As a moderator could you move this post to Garage/ Mechanical Help.
This was my first post and of course I put it in the wrong thread.

Thanks for your response. Ken

[wolfc70]

Um, did you try starting the bike with the tank up? That might have caused the fuel pump to suck air and do the fire then die thing. Just a thought.

[Red FZ6 Rocket]

Yes it was up about 4" so everything could be connected before starting. I have a little over 1/2 a tank of gas so I wouldn't think the fuel pump suck in air. But thanks for your response. Ken

While the vent hoses were unpluged I tried increasing the idle screw thinking maybe it changed a little but no luck even after 5 complete turns it still would only fire and than die.

Well it's time to go rack the brain and figure this out , I check back later. Ken

[Red FZ6 Rocket]

Well my bike started right up as usual ,then I pulled the bolts out of the vents and nothing happen she kept on running. So I shut off the motor and tried to restart and it fired right back up with no problems.

I'm not sure if something was suck and freed itself overnight but so far so good.
I rode 10 miles to the auto - parts store and back with no trouble so I have regained my faith in the FZ.

Thanks for the input from everyone problem solved (Fixed Itself)

[wolfc70]

Originally Posted by Red FZ6 Rocket

Yes it was up about 4" so everything could be connected before starting. I have a little over 1/2 a tank of gas so I wouldn't think the fuel pump suck in air. But thanks for your response. Ken

While the vent hoses were unpluged I tried increasing the idle screw thinking maybe it changed a little but no luck even after 5 complete turns it still would only fire and than die.

Well it's time to go rack the brain and figure this out , I check back later. Ken

It could have been the problem. The pump and pickup are low in the tank and there is a large cavity (space) near the bottom/back of the tank. With a half tank you "could" have sucked air. I'm not 100% sure, as I have not taken the pump assembly out. Glad it seems to be working fine again.
Justin

[Red FZ6 Rocket]

Wolfc70 you may have been right. Well I know I will not be starting the motor with the tank raised up anymore or without at least a full tank of gas. I'm glad she's back to normal.