'04 AC 400 4x4 auto FIS - Idle, Die, Run Brain Teaser

[kctm]

I have a 2004 4x4 automatic FIS with a Keihin CVK34 carburetor. Here's the situation: It starts immediately with the choke open and idles fine for three to four minutes and then dies. If I try to start it again, it won't start. If I move the choke to fully closed it runs for about thirty seconds and then dies again. If then I move the choke to any position it won't start. At this point I wait between thirty minutes to an hour and then try again with the choke open. It starts immediately and runs perfectly. The next day I go through this scenario all over again. I cleaned the carburetor which wasn't dirty to start with but that didn't cure the problem. I also checked the choke cable travel for the hell of it and it operates smoothly. By the way I seldom need to use the choke to start it initially. The only time the choke seems to have any effect is when I start it the second time and it runs for thirty seconds.

Any ideas would be greatly appreciated. Thanks!!!

[TORK]

Sounds like Your not getting fuel to the bowl of the carb. First start you are using what's in the bowl, but are not replacing the fuel you used fast enough. Second time you have a little fuel trickled into bowl, start with choke to get enough to run and it dies. Let sit long enough for the trickle to fill bowl and you run for the longer time. You need to check fuel flow out of tank to carb. If that is ok pull carb back off and remove needle and seat. There is a screen on the back of the seat that is a filter. If you have good flow to the carb then your restriction could be there.
Hope this helps, TORK

[Bear4570]

Have you tried it in the Reserve position on the tank shut off valve? Tork is right, it is a fuel feed problem. FYI, it is not a choke with a butterfly valve, but and enrichment system. I just adds extra fuel into the intake to make the motor better run when cold. No fuel in the carb and it can't work and more than the butterfly type choke can.

[swampyjunior]

I seem to remember reading a technical bulletin on AC fuel problems similar to this situation. Had something to do with an O-ring on the fuel shutoff valve tearing and blocking the flow of fuel.

I don't remember if it blocks it at the valve or the chunk lodges in the carb.

I would think that if it is starving for fuel that the RPM's would increase just prior to it dying? You did not mention if this occured.

You may need to check the plug right after it does to see if its wet and black which would mean it is getting too much fuel.

You might also check to see if you have the same problem when the fuel valve is in the reserve setting.

Hope this helps

SJ

[kctm]

Originally posted by: TORK
Sounds like Your not getting fuel to the bowl of the carb. First start you are using what's in the bowl, but are not replacing the fuel you used fast enough. Second time you have a little fuel trickled into bowl, start with choke to get enough to run and it dies. Let sit long enough for the trickle to fill bowl and you run for the longer time. You need to check fuel flow out of tank to carb. If that is ok pull carb back off and remove needle and seat. There is a screen on the back of the seat that is a filter. If you have good flow to the carb then your restriction could be there.
Hope this helps, TORK

Thanks to all who have responded to my post. Following Tork's suggestions I first checked the fuel flow from the gas tank to the carburetor. I attached a hose to the gas tank valve and put the other end into a gallon wine bottle. I turned the valve to ON and watched the flow of gas. It seemed to be slow at first and then even slower. I suspected that vacuum might be building up in the tank. Next I removed the gas tank vent hose from the tank and from the interior of the atv. I blew air into the hose and noted no restriction. I reattached the hose to the gas tank and rerouted the other end into the interior of the atv such that there was no possibility of pinching of the hose. I then checked the flow of gas from the gas tank valve into the gallon wine bottle and noticed a remarkable increase in flow volume that continued without dissipation. Realizing that gas flow, as Tork had mentioned, might be the problem and probably was, based on this experiment, I started the atv and let it run for fifteen minutes. And as expected it did not die. After the fifteen minute period I shut it off. I removed the gas tank cap and listened to see if air would suck into the tank. It did not. No vacuum as suspected. Needless to say I am a "Happy Camper" and sincerely appreciate the help all of you have provided me in solving this problem.

[TORK]

Glad we could help and that it was simple and cheap to fix. Tork