I recently bought a John Deere STX38 black deck with a Kohler Command CV125S. The guy said it ran fine for the past three years he’s had it, but wouldn’t start this season. After about ten seconds of cranking with the choke on, the mower will briefly fire, but die within 2-3 seconds. I have replaced all fuel lines, fuel filter, fuel shut off valve, cleaned the tank and fuel cap vent, and and ignition module. I cleaned the carb, but have not rebuilt it. I tried resetting the carb adjustments, but it didn’t help anything. Other than this issue, the mower is in excellent condition. Thanks for any help!
I would make sure you have a good flow to the carb by pulling off fuel line at carb....fuel should flow from hose if it’s gravity fed. If you have a fuel pump spin the motor and fuel should pump from hose. If you have good flow you more than likely have a carb issue.
Time to do some testing.
Tip a little fuel down the spark plug hole & crank the engine
Fires right up for a second or so = timing is right & ignition module is working
Do the same down the carb throat
Engine starts then runs off the fuel = valves are also good & your problem is in the carb.
Replace the carb solenoid with a bolt
Engine fire up & runs = defective solenoid
Check that the choke is closing fully, if not adjust the cable at the cable clamp to make sure it is closed fully.
