Defective spark plugs

Defective spark plugs will either prevent fuel from igniting or ignite it at the wrong time. This will cause stalling, failure to start, or a reduction in engine power.

Table of Contents

• 1. Symptoms
  • 1.1 Engine Stalls
  • 1.2 Engine Will Not Start
  • 1.3 Knocking

Symptoms

Engine Stalls

With defective spark plugs, one or more cylinders will not fire. This will cause the engine to stall as it will not have the power to maintain the power cycles.

If the engine can fire some cylinders, but not others, the engine may struggle a bit before stalling.

Engine Will Not Start

If the engine fails to start, but the starter motor is still cranking the crankshaft, the engine will not start. This may be the result of multiple defective spark plugs.

Knocking

A spark plug that fires too early will cause knocking, a metallic sound from the engine. A damaged spark plug may be heated to the point where the fuel is ignited before the spark.