18hp koler on a troy built will not start even i jumped with my truck. it w?

With the key off, try turning the engine my hand top make sure it's loose. If it is tight take the plastic cover off the top of the starter to see if the pinion gear is stuck in the flywheel ring gear. If the engine turns by hand suspect the solenoid.
The solenoid will have the heavy wire from the starter on one post and the positive wire from the battery on the other post. You can test the solenoid by shorting the posts out with a heavy screwdriver or jumper cable with the key on. If the engine trys to crank when the posts are shorted out the solenoid is bad.

Rick
May 2006