I have a walk-behind self-propelled Troy-Bilt mower that won't start. It is almost three years old and has been self-serviced regularly. It has a B&S motor with the red prime pump. It has run well until recently. The other day, I put diesel fuel in it by mistake. It ran sporadically for a few moments and then died. It (obviously) wouldn't restart. When I realized it was diesel in it, I drained the tank and fuel line to the carb. I spray cleaned everything with carb cleaner including the tank and lines. I put some carb cleaner in the tank and mixed it with a little gas; it started up and ran just fine... for the time. Once I started mowing, I started it cold and it started just fine and ran well with no issues. When I had to stop it, however, to empty the bag, it would not restart hot. I pulled the rope 20+ times with no attempt to start. I let it cool down (several hours) and then it would restart, though it took a little effort to do so.

After it was running I pushed the mower under a weeping Japanese maple and somehow the gas cap came unscrewed. I mowed over it before I discovered this fact. I took another cap off an old mower, and used it as a replacement. (I don't know if my original cap was vented or not, but the replacement cap came off an older Troy-Bilt and I think it is non-vented) It started up (once cool again) and ran for a few minutes and died. I took the cap off (didn't hear a vacuum sound) and tried to start it without a cap and it would not start. I let it cool and it would not start either. I even waited to the next day, and with the replacement cap on and loose or off completely, it will not start. I have pulled the rope 20 to 30 times and no start... not even an attempted start.

What could be wrong? Am I getting a delayed result of putting diesel in it, or could something be further damaged or corroded due to the diesel? I am at a quandary as what to do. This mower is only three years old and I would like to get more service out of it, plus I would hate buying a mower this late in the season.

Do any of you pros out there have any ideas what I should do. First, why was it so hesitant to restart when hot. Second, why is it completely dead now and will not start at all. I just can't figure out why it did mow after cleaning out the diesel and why it died suddenly with the replacement cap and would not restart at all after putting the replacement cap on. TIA for any help!

Do the following. Remove the plug. Spary carb cleaner in the plug opening. Pull the cord a few times with a rag over the opening. Replace the plug with a new plug. See if it starts.

If it doesn't verify that you have fuel, fire and air. AIr is easy - start with cleaner off. Fire is easy. Hold plug against chassis and look for spark. Fuel is easy. Check for a wet plug.

Don't use startting fluid to try to start a small engine. Use a little carb cleaner in the spark plug hole. If it sputters, it's a fuel problem.