MF35 cuts out after warm

[twosocks90]

As the title says, my MF35 cuts out after it warms up. When mowing at full throttle, it runs fine until the engine warms up. After that, it will hit and miss. That is, runs up to full RPM, then cuts out until RPMs drop to around 1500 or so. Then it kicks back in, runs up to full speed and cuts out again.

I just got the tractor last fall. The ignition system (points, cap, rotor, coil, wires, etc) looks pretty much new but that's no guarantee.

Any suggestions on how to find the problem?

 

[MrJimi]

Coil or condensor, pour some cold water on it and it should start right up after it quits and if it does, just replace it

 

[twosocks90]

It never actually stalls. RPM's go from 2200 down to 1500 and back to 2200 again, over and over.

 

[Farmwithjunk]

It never actually stalls. RPM's go from 2200 down to 1500 and back to 2200 again, over and over.

Would you describe it as a "pulsing" of the motor? If so, there's a dampener on the governor that may need adjusting. If so, post back here. I'll try to link you to someone who can walk you through the adjsutment. I know how, but have a real time explaining it.

 

[Zoombah]

Try posting your question over at Antique Tractors - Yesterday's Tractors : Antique Tractor Headquarters. I'm amazed at the depth of answers I get when I post questions about the MF35 I have.

 

[twosocks90]

Would you describe it as a "pulsing" of the motor?

No. The motor actually seems to cut out. I don't believe it's running (ie fuel igniting in the cylinders) while the RPM's are falling. It reminds me of our Chevy Malibu where, when it hits redline, the computer cuts the spark (?) until RPM's drop again. This is similar to that in, when it warms up and is running at max RPM's, it begins to cut out slightly (a few hundred rpm) then go back to max, then as it gets warmer and warmer it drops to lower and lower rpm's before kicking back in again. The lowest rpm it gets to is 1500.

 

[Zoombah]

OK. I checked archives over at Antique Tractors - Yesterday's Tractors : Antique Tractor Headquarters. The folks over there suggest coil, condenser or plugged vent on fuel cap. Coil and condenser are inexpensive enough that I'd just replace them even though they look like they might be sort of new. Plugged vent on fuel cap could cause fuel starvation. To test the fuel cap just loosen it a bit when the motor is warmed up and acting up to see if the cutouts stop.

 

[twosocks90]

Thanks Zoombah.

 

[Grrrr]

I would say it was a fuel problem. It probably isn't getting enough fuel to run properly.

 

[bcsawyer]

I have experienced that problem with our 35 and with a Ford pickup I used to have. Everyone said that it wasn't the coil, but a new coil fixed both of them.

 

[ToadHill]

I agree with most all. The solution is a new coil. I had the problem with a couple of old vehicles I've owned and in both cases the coil failed when it heated up.

 

[twosocks90]

The problem turned out to be wasp nests in the air intake hose before the air cleaner. Under load the engine wasn't getting enough air and it was choking out. After cleaning out the nests it runs great.

 

[WilliamTO-35]

Speaking of wasps, I've had some odd problems that were due to mud wasps plugging up small holes that should have remained open. One such problem was a plugged float chamber vent in a carburetor, which caused the carburetor to flood. Another was a fire extinguisher that didn't work at a critical time because the nozzle was plugged by mud wasps. I now keep a plastic cap over my fire extinguisher nozzles, put on loosely so that it keeps the wasps out but will easily blow off if necessary. A small piece of aluminum foil would probably work as well.