My friend has a 2004 model John Deere LT160 Lawn tractor, it's got 206.* hours on it right now. We used it Thursday night, and it worked great for us. Last night when we tried to use it again, it just wouldn't start. It's got a Kohler 16hp motor in it, and the problem is like this. It'll crank and crank, but never starts. When we pulled the plug it was wet with fuel. You can smell raw fuel coming from the exhaust. If you crank it for a bit, sometimes it will backfire. We took the safety switch out of the seat and tried operating it manually, didn't make a difference. Also tried starting it with the switch unplugged, same symptoms.

Is it possible that it's the "seat safety switch" is causing this problem?
What should else we be looking at?

Thanks for the help

It is not the safety switch. The switch will not allow the engine to crank at all unless you are seated. I'd check the carb bowl, specifically the float and needle valve. You are flooding out. Be sure the valve seats when you raise the bowl.

It is not the safety switch. The switch will not allow the engine to crank at all unless you are seated. I'd check the carb bowl, specifically the float and needle valve. You are flooding out. Be sure the valve seats when you raise the bowl.

Well originally I thought that also, but the Mower still cranks regardless of you sitting in the seat and it also still cranks with the seat safety switch unplugged. So we should be looking at the carb? It just seems odd the carb would be working 100% one night and two days later it won't start at all.

Carbs can go bad instantly if a spec of junk gets down the fuel line and reaches the needle valve. Sometimes you clear the obsruction just by opening the bowl and allow some fuel to leak out as you raise and lower the float. I'd check this next. However, read your manual, I don't like what you say about that safety switch. It does sound right to me.

The safety switch works to short the coil out and kill the engine as well as stop it from cranking. I would isolate the coil by disconnecting the small black wire coming from under The flywheel housing, this will at least tell you if you have a switch acting up.

Don

Hey Green, you never mentioned if you checked for spark. Pull the plug and put the wire back on it. Allow the threads to ground againist the block and turn the starter. You should see a blueish spark.

We'll have to check for spark next time I get a chance to look at it, and see if we can disconnect the coil shut off. I'll check and see if that changes anything.

Ok, the spark is good.

Tonight my friend's dad took the carb bowl off and checked the float. He says it looked good, where should we go next on the carb? When we crank the motor over, it will crank but sometimes when we stop cranking it will backfire out of the exhaust. Does the timing ever come out of adjustment?

Tonight we completely took the carb off and cleaned it out with carb cleaner. I checked the float, took it off and cleaned it. We assembled it again and tried to start it and nothing changed. We tried putting a spoonful of gasoline into the carb throat and also spraying carb cleaner into the carb and it didn't make a difference We noticed that while cranking, sometimes we'd get "backfire" up through the carb. I'm not sure what that means. It would still backfire out of the exhaust also. What else could be causing these problems?

Remove valve covers, watch valve travel or look for the obvious, I think you will find your problem there.

Don

You might have a bent vaulve if your getting back compression through the carb

Hello Green, did you ever find what was wrong?

Yes, the flywheel had shifted so it was out of timing

Great, thank you, I will start looking that direction. Mine is an '06, but doing exactly the same thing.

Thanks for the help. Same thing happened to my 2002 LT160. The woodruff key that holds the flywheel in position sheared off. Fixed it for $1.01.

Very old post, but putting a thought here for anyone else that might trip on this. The seat safety switch engages after the PTO is engaged (mow deck blades engaged). It will not prevent the engine from starting or stop it if the blades are not engaged/spinning. That is why you can stop, put on the parking brake, disengage the blades and then get off the mower while it is running to empty the bagger or do other quick tasks without having to re-start the mower.