Choosing And Using A Tractor

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The switch is turned on? In that case, one of two things is wrong: Either the cylinders are not getting fuel, or the spark plugs are not receiving enough current from the battery and ignition coil to ignite the mixture of air and fuel. (I'm simplifying. There are actually several other possibilities, but those two are the most likely and the easiest to test.) Try the gas first. Use the correct size wrench to unscrew the fuel line where it enters the carburetor; you should see a fine, steady stream of gasoline flowing from it. If you don't, add a few gallons of fuel to the tank—even though you can see gas in the tank, there may not be enough to reach the level of the outlet line—and look again. If you still don't see any gas flowing, you have a clogged fuel line, filter, or shutoff valve. Examine the system and repair the culprit.

If you find that gas is getting to the carburetor and the engine still won't start, check the spark plugs. Remove the wire from one of the plugs, unscrew the plug, and reconnect the wire to the plug. Now rest the metal base of the plug on the axle, steering rod, or some other heavy steel member (rub it back and forth a few times to be sure it's well grounded). Take your hands off it—if you don't, you'll soon get a sharp electric shock—and push the starter button (make sure the ignition switch is on!). You should see a strong blue spark leap across the gap of the spark plug (Fig. 14). If you don't see a spark, you have an electrical problem. In that case, check that the points are properly gapped, that the rotor and the inside of the distributor cap are clean and dry, and that the distributor cap is firmly fastened down. If the plugs still don't spark, it may be because the porcelain insulators are wet or dirty, either of which can temporarily short-circuit the plugs and prevent them from sparking (or allow them to spark only feebly). Wipe the exposed porcelain surfaces of the plugs, and if they are very wet or if the tractor has sat unused in damp weather for some time, remove them and dry them completely by putting them in a warm oven for half an hour.

Still no spark? My final suggestion is to take out the ignition coil and have it tested—and if that proves OK, the problem is a bad wire somewhere in the system, or possibly a defective ignition switch.

If you get a strong spark at the plugs and gas is getting to the carburetor but the engine refuses to start, there's probably a glitch in the carburetor itself. In order to give the carb a going-over, you'll need to shut off the fuel line at the tank and remove the carburetor from the tractor.

(Before doing that, some people like to give the cast-iron body of the carb a smart tap with a wrench and try the starter again. The tap is sometimes enough to jolt a stuck float valve loose again—at least temporarily. Another worth-a-try approach is to hold the palm of your hand over the carb's air intake, crank the starter for a few seconds, and jerk your hand away as you continue to push the starter button. Sometimes the sudden surge of air pressure that results from this maneuver is enough to blow out any deposits gumming up the carburetor's inner workings.)

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