When to Replace Lawn Mower Spark Plug?

What exactly does the Spark Plug do? The spark plug provides an ignition source for all small gas engines, such as the kind that powers a lawnmower, weed trimmer, snowblower etc. A spark plug is made fairly simple. It has a center electrode encased in a protective porcelain sheath, a firing electrode and a threaded shank for its installation into the engine block. Most often, when a lawn mower’s spark plug goes bad, mowing can be very challenging. Below are a few symptoms that you may experience when it is time to replace your spark plug on your lawn mower or gas engine.

Physical Appearance

By inspecting and removing the spark plug and its appearance can give you further clues about whether or not it is time to replace the spark plug. Its center electrode should have a flat top. If its top is rounded, then the spark plug must be replaced. Also, look for cracks or “chips” in the spark plug’s porcelain sheath. Any damage you see to the spark plug requires its replacement. If after inspection, if you see the spark plug is in good shape but is black with carbon build up or wet with gasoline, then a you must give the spark plug a good cleaning with a wire brush.

Poor Engine Performance

When the engine finally begins to start but tends to die out immediately there is something wrong with the spark plug. In some cases, the engine may run for a while then stop while mowing. Each time the engine dies, it must be restarted, which usually proves more difficult as the engine warms. Heat causes expansion, which can significantly increase the gap between the spark plug center and the firing electrodes. A bad spark plug may also cause misfires, which resembles the engine sputtering or popping.

Lawn Mower is Hard to Start

This is the most common problem associated with a bad spark plug in a lawnmower. There are different types of lawn mowers however a push mower may take several more pulls on the starter rope before its engine starts. The spark created by the spark plug may be too weak to ignite the fuel and air mixture that the carburetor already delivered into the cylinder. This most often leads to the engine flooding as more of the mixture enters the cylinder.

Excessive Fuel Consumption

You may notice your lawn mower engine seems to be consuming a ton of gas, the spark plug may be the cause. Often when there is a poor spark, gasoline does not burn completely or burns inefficiently. This results in that the mower’s fuel consumption increases and its fuel efficiency decreases significantly. In this scenario, the fuel may not be fully burned and poor firing also may lead to the presence of the odor of raw gasoline as the mower is turned on during use.

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