How to check spark plugs with a multimeter

Spark plugs sometimes fail or start to work worse. To determine such deviations, you can use multimeter. With its help it is easy to check all the spark plugs in just 1 minute.

Spark plug testing process

To check you need to switch multimeter into 20 kOhm resistance test mode. With its help, you need to measure the resistance on the central electrode between its open edge and the contact nut. It should appear only when the probes touch its ends. If multimeter shows resistance between the housing and the electrode, then the spark plug is faulty.

The central electrode provides resistance because there is a resistor on it. Its task is to reduce the arc, since otherwise it will gradually melt the electrode, shortening it, which will cause the gap on the spark plugs to constantly increase. This internal resistor also minimizes radio interference produced when the spark is ignited. You need to check all the spark plugs with a multimeter. It is important that they have approximately the same resistance, then the engine will operate stably.


If, when checking old spark plugs, those that have significantly changed their resistance are found, then they should be changed.For most internal combustion engines, spark plugs with a resistance of 5-15 kOhm are suitable. Knowing what it should be like on the standard spark plugs of a particular engine, you can select their analogues, which have the same value.

It is also possible to detect spark plugs with zero resistance using a multimeter. They are installed only on certain types of engines. If you accidentally install them on a regular motor, then as a result you can disable the “brains”. It is always worth rechecking new spark plugs, since if their resistance parameters differ from the permissible value, then you can end up with serious repairs or at least destabilize the operation of the engine.

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