Cub Cadet with Kohler 7000 Series: Engine quitting and restarting

[JD4JC]

Long time lurker, first time poster. I have really enjoyed the discussions and wisdom on the forum!

I have a 2015 Cub Cadet RZT L Tractor with a 46” deck, and powered by a 23 HP Kohler 7000 Series 725 cc vertical engine, that has given outstanding service. Recently, while under full throttle, the engine has stuttered and momentarily quit. So far, I have been able to keep it going by disengaging the blades and closing the choke briefly. These occurrences have happened during the recent hot weather after about 1.5 hours of full-throttle operation

I replaced the fuel and air filters and thought I’d found the problem, but today with a 90º ambient temperature, after about 1.5 hours it quit again but could be kept running with manipulations of the throttle and choke, and would continue to run for 10 minutes or so until the process had to be repeated. I let it cool off for an hour, and the problem seemed to have disappeared, and I finished the mowing job in about .5 hours.

Years ago, I had similar experiences with the vehicles of my youth, and the problem was usually a vapor-lock. I’m wondering if it’s possible that something like that is happening. One other possible factor, the gasoline in the tractor is several months old, and was treated with StaBil fuel additive when the gas was purchased.

Any thoughts on this would be much appreciated!

 

[StarTech]

Yes it possible especially with several months old as it could be a winter blend.

And yes I have seen fuel to be boiling in see through fuel filters where excess heat was heating the fuel lines. Winter fuel boiling point can be as low as 140F.

 

[JD4JC]

That's gotta be it. I'll get some fresh gas and see if that fixes it. Many thanks!

 

[Charlie8d]

Old fuel, trash, crud from the ethanol could still be lingering in the tank & carb. Just adding fresh gas & a new fuel filter may not fix this.

 

[JD4JC]

I have a friend who's retired from being an engineer at John Deere. He said that the ethanol plus the altitude here (6140') and 90º+ is surely the culprit. He suggested a temporary "field fix" is to add cooler fuel to the tank. He also sent me a chart showing the effects of temperature and ethanol concentrations. Sure shows the adverse effects of the ethanol levels!

 

[Fiver]

I have a friend who's retired from being an engineer at John Deere. He said that the ethanol plus the altitude here (6140') and 90º+ is surely the culprit. He suggested a temporary "field fix" is to add cooler fuel to the tank. He also sent me a chart showing the effects of temperature and ethanol concentrations. Sure shows the adverse effects of the ethanol levels!

I am having the exact same problem (same mower but troybilt). I siphoned out the tank (had 3 months-old gas/ethanol), then ran fresh gas with seafoam. It seemed to run better when idling, but would not cut for long without cutting off. Did non-ethanol gas solve the problem? Or were you able to resolve it otherwise?

 

[Fiver]

I am having the exact same problem (same mower but troybilt). I siphoned out the tank (had 3 months-old gas/ethanol), then ran fresh gas with seafoam. It seemed to run better when idling, but would not cut for long without cutting off. Did non-ethanol gas solve the problem? Or were you able to resolve it otherwise?

Today I disassembled the gas tank and washed it out. I had accumulated a lot of debris in the tank from the cap coming off when I mow along a pasture fence. I blew out the fuel line with compressed air and changed the fuel filter. Then I added fresh gasoline and a healthy amount of Sea Foam. It ran well with only one hiccup as I mowed for the next hour. So far, so good. It is now at 250 hours.

 

[Charlie8d]

Fiver,
You may want to change the spark plugs, or at least clean them, to help it along. Continue to run that tank with Seafoam in it til it is low. I only use ethanol free gas.

 

[Fiver]

Fiver,
You may want to change the spark plugs, or at least clean them, to help it along. Continue to run that tank with Seafoam in it til it is low. I only use ethanol free gas.

Thanks! Last night, when ran low, I poured the rest of the SeaFoam in when refilling the tank. By the time I was done mowing, it was running very well. Good idea, I'll change the plugs when I change the oil, oil filter, and air filter. Using non-ethanol gas is on my list, too.

 

[Charlie8d]

I live in hot, humid Florida, & we are getting soaked by monsoon rains. Regular gasoline does not last long in these conditions, unless treated with something.