MF 135, cuts out when hot, almost like vapor lock????Help

[sch2046]

I have an early 70's (I think) MF 135, gas engine. It has the gas tank on top of the engine, which seems odd, but when I run the tractor and am cutting my grass, it runs fine until it starts to get hot, then it sputters and misses and eventually stops. When it cools off, it runs fine again. Does anyone know what in the heck this can be. I got it last year and it didnt do this last year. It almost seem like the gas is getting too hot and I am getting some kind of vapor lock or something.........
thanks for your help,
Sean

 

[murphy1244]

could be time for a valve job.

 

[whistlepig]

Might be a gas cap with the vent plugged. Run it a bit then stop the motor and slowly open the gas cap. If you hear air sucking in its a plugged gas cap vent.

 

[sch2046]

Thanks, I will check the gas cap tomorrow. My gas cap fits very loose though. It doesnt seem like my valves are out, it only sputters and stops once it gets hot. It starts right up.

 

[pjbci]

My 135 does the same when its time to replace the coil. Maybe this helps you.

 

[Wacky]

My 135 does the same when its time to replace the coil. Maybe this helps you.

This could very well be it! When the coil gets hot, the windings expand. If a winding is broke it may come apart just enough to cause what you describe. Cools back down and the winding makes contact again. Kudos to pjbci for chiming in with the same issue!

 

[bakerg]

My father had a 1971 GMC pickup that would stop when it warmed up. He found that the distributor cap was cracked and was causing the problem.

 

[The kid]

I have an early 70's (I think) MF 135, gas engine. It has the gas tank on top of the engine, which seems odd, but when I run the tractor and am cutting my grass, it runs fine until it starts to get hot, then it sputters and misses and eventually stops. When it cools off, it runs fine again. Does anyone know what in the heck this can be. I got it last year and it didnt do this last year. It almost seem like the gas is getting too hot and I am getting some kind of vapor lock or something.........
thanks for your help,
Sean

Is your heat shield still in place. This is a piece of metal that surround the exhaust manifold and prevents the tank and other areas to get hot. If you have an external fuel filter close to the manifold (metal can type) could possibly cause a vapor lock. Unvented cap or a pressurized cap could cause problems. I bought what was described as a vented cap, but actually a pressurized vented cap. I modified the pressure release to make it a vented cap. As another described, when it quits, twist the cap to see if it's under pressure. The coil is another good tip. A bad coil will open under heat. Although if it's a Continental engine, that side doesn't get neat as hot as the other. Make sure your coolant level is correct. Make sure your radiator front is not full of debris.

I had the exact same thing happen to me. It was a vapor lock in the fuel filter close to the manifold. My heat shield was missing and replaced it with a good used one. I also converted the high pressure fuel line to a metal line bent so as to be well away from the manifold. FYI the manifold can get 500 degrees and higher, so anything close to it is volatile. The coil can be checked directly after a shutdown. Put a paperclip in your pocket. Put the tractor in neutral (s) set your parking brake, pull the closest plug wire to the dash and see if you get a spark with a paperclip installed and place near spark plug while cranking. Should be a nice blue spark. No spark, bad coil. If the heat shield is missing see my Refurbish thread where I replace it. Good luck. Take some pictures of your tractor and post them. -Robert