John Deere Maintenance Monday: Lawn mower spark plug condition
Having trouble starting your lawn mower? You may want to look at the spark plugs.
Radio interview source: Shane Louwerens, John Deere Ag Tech Instructor, Northwest Mississippi Community College
In this edition of Maintenance Monday, we're answering a question from Mark in South Carolina. He's had trouble getting his lawn tractor started and is suspecting a spark plug issue. However he's not sure how to tell if the spark plug is bad or something else is wrong.
Shane Louwerens is a John Deere Ag Tech Instructor at Northwest Mississippi Community College. He says the spark plug is a work horse. Just mowing a yard for two-hours means the plug will fire about a-million times. It carries thousands of volts and has to withstand high internal combustion and engine temperatures. Over time, the spark plug is going to break down, so if there are troubles, inspect it.
"You pull your plug out and it's wet, then of course it's not firing because you have fuel on it, and you should not have fuel on it," he says. "It doesn't need to look burnt, discolored. When you heat metal it turns kind of bluish and different colors. The ceramic insulation around the tip needs to be inspected, it shouldn't be chipping or powdery. It needs to be a real nice glassy-type condition."
If it looks fine, Louwerens says to check the plug wire to make sure there is electrical current reaching the spark plug.
"Easy way to do it is take your plug out, put it in the wire, ground it to the frame or an engine part, and turn your key over holding the insulation of the plug wire," says Louwerens. "And if you see a spark, then of course you know your engine electrical part is working. So it is actually throwing a spark, but that is when you need to check your spark plug gap, the distance between your ceramic and the actual tip."
Too small of a gap means too small of a spark. If the gap is too wide, it may be missing the connection because it's too far for the spark to jump.
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