To troubleshoot a tractor, first determine the problem with the machine; for example, if the tractor does not start, check to ensure that there is an adequate amount of new fuel in the gas tank. If there is old gasoline in the tank, it may have deteriorated. Siphon out the old fuel and replace it with fresh fuel, and then try starting the tractor again. Ensure the oil reservoir is full, and consult the owner's manual for more information.
Faulty spark plugs or a dead battery can also prevent a tractor from starting. Attach a voltmeter to the battery to test the voltage. If the voltage is adequate, disconnect the battery and clean the leads; they should be free of dirt and debris to ensure a good connection. If this does not help, check the spark plugs to make sure they are all properly connected. Replace broken or dirty spark plugs with new ones. You can also clean dirty plugs with plug cleaner.
If these steps do not solve the problem, check the valve system to ensure that the correct amount of air flow is reaching the engine. If there is not enough pressure in the system, replace or repair the carburetor using manufacturer-recommended parts. Check the air filter, and replace it if it is dirty. Ensure that the system is appropriately sealed and that the fuel line is not blocked before trying to start the engine.
In some cases, a tractor may start, but the engine may perform poorly or produce white or gray smoke. The cause of this problem may be an improperly filled oil reservoir. Other causes could be a broken head gasket or an incorrect oil grade. Fill the oil reservoir with the appropriate type of oil, and inspect the crankcase for leaks.