How to test your tractor for faulty spark plugs

3/14/2016 10:48:22 AM by Tractor-Part

Let's say you're headed out in the early morning to work in the field. Your tractor is old, but it's run well since you first bought it several years ago. There hasn't been any major issues, just a few occasional, minor repairs. But today is different. Today it's not starting like it usually does. The engine is running rough and doesn't have a lot of power. You also have to constantly turn the starter to start the tractor, and black smoke spews from the exhaust whenever you do.

You begin to worry you may need a new tractor. But don't fear, there's a good chance it only needs a tune up. Here's how to get it done.

  1. Warm the engine to operating temperature.
  2. Clear away dirt and debris from the engine and use a paint brush to apply a can of engine cleaner to the unit. It's much easier to work on a clean engine. Let the cleaner sit for the amount of time required, which will be indicated on the can. During this time, the cleaner will dissolve grime and buildup. Once the allotted time is up, hose the engine down.
  3. Carefully remove and inspect the plugs. Usable plugs will still be lightly gray or tan, indicating the upper part of the engine is likely in good shape. If the plugs are covered in black carbon, there could be a no fire condition or excess oil in the engine.
  4. If you think there is a no fire condition take a good, clean spark plug and connect it to the corresponding spark plug wire. After safely securing the plug, turn on the engine a couple of times to see if there is a spark. If the replacement plug sparks, try using the older plug again. If the old plug still does not spark, clean the plug and repeat the process. If it still doesn't spark, it's likely shorted out.
  5. Other engine tests include determining the oil penetration to the combustion chamber using a compression tester. A tester looks like a pressure gauge with a hose that which screws onto the spark plug hole. Check all of the cylinders using the tester. Your engine manual will tell you the engine's specific psi compression specs. If you don't have the manual, you'll generally want to look for a consistent reading across all spark plugs. If, for example, four out of five plugs are at 70 psi and one is way up at 120 psi, there's a good chance the latter has a lot of carbon buildup.