Нow to check a spark plug in a car.


The effective and long-term operation of the ignition mechanism in a car depends on its operating characteristics. Special attention is required for such details as spark plugs.

If your car has problems like:

  • Weak spark,
  • High fuel consumption,
  • Check Engine is glowing,
  • Slow acceleration or the engine is hard to start,

so it’s time to check spark plugs.



If it is necessary to replace bad spark plugs, then choose the same brand and the same manufacturer that was installed earlier.


What do you need to know about the test and where to begin?

Read the instructions for testing the spark plugs.

Sparkling parts are affected by various factors: temperature, pressure, gravity, etc. Be attentive to the evidence of a residue at the ends of the spark plug electrodes, check for oil leaks.

No spark is a common problem that is solved by certain manipulations. A special tester (a spark plug tester) is used to detect this problem.


In addition, there are a number of reasons why these details may fail:

  1. Wear of the electrodes and materials of the mechanism;
  2. Soot/residue formation in the emitters;
  3. Formation of the oily film;
  4. Because of the usage of oil with special impurities (e.g., ferrocene), a lacquer membrane is formed in the planes;
  5. Damage to the main electrode due to combustion or mechanical action.

Symptoms of a bed spark plug.

Malfunctions must be addressed before an ignition system can be tested. Common symptoms that indicate impairment of a spark plug are:

  • The crankshaft rotates correctly, but the engine does not start.
  • Ignitions are detected in one or several cylinders, resulting in unstable engine operation.
  • The car breaks down if the «launch system» stops rotating;
  • The reserve margin is reduced, which leads to excessive consumption of fuel.
  • Catalyst failure.
  • Prolonged engines start at low and very low temperatures.
  • Different mechanical defects in the sheathing of spark elements.

How often do you need to change the spark plugs?

The frequency of replacement of spark plugs depends directly on the type and brand of your car. Also, it depends on the recommendations in the vehicle’s maintenance folder.

Qualified specialists recommend changing spark plugs every 30,000 km. Platinum and iridium spark plugs – every 90-120,000 km.


Supplies required to verify the spark plugs.

If the engine starts to work intermittently or strange sounds are heard during the start-up period, this indicates that there are problems with the details that give a spark. Here it will go about their contamination.

These elements may be tested for ignition by such methods:

  1. To use special instruments or testing devices made for this purpose;
  2. Manual checking.

two spark plugs


How to clean a spark plug

There are several methods of removing unnecessary particles (residues, impurity, etc.) from the spark plug which are formed during the operation of a vehicle. The following methods are distinguished depending on the type of cleaning-up:

  • Mechanical (by metal brush with thin bristles).
  • Chemical (20% ammonium acetate, carburetor washing solutions, or solutions with orthophosphate or hydrochloric acid).
  • Thermal (using high temperatures).
  • Ultrasound.

An ultrasound method implies the usage of special devices. The surface of details becomes extremely clean after this method of cleaning.



7 Steps guide to change spark plugs quickly and easily.

  1. Preparatory phase.

All holes in which the spark plugs are placed are carefully cleaned. The removal of dirt and dust is recommended to make with soap solution or special detergent. It is better to use a hard brush to remove the rough dirt. Then all cleaned areas are dried with a napkin.

         2. Disconnect wires with pliers.

If your car has an injection system, disengage and unscrew the ignition coil.

          3. Getting a broken spark plug out of a cylinder head.

These parts shall be got out by a special spanner. This instrument is put on the top of a spark plug and scrolled, according to the technology of the classical tighten key;

         4. Inspect the spark plugs on the availability of residue and contamination. If there are signs of corrosion or oil on the electrodes, reexamine the distributor lid, the rotor and purge the carburetor.

           5. Installing a new spark plug.

It is necessary to tighten the consumables with the help of a spark plug gap tool or a probe. It should be done very carefully because incorrect installation of these details can have a negative effect on the operation of the engine. If the gap of a spark plug does not match its special parameters, it can cause problems with the process of ignition.

            6. Insert carefully the spark plug and tighten it using a dynamometer key. Once the spark plug is replaced, it is important to remember the wiring that was connected to the old one.

             7. Start the engine. It is the final step to verify the correct installation.


How to test the spark plugs with a multimeter.



Take a multimeter and set it to 20 kOm. The resistance of the spark plug is checked between its central electrode and a contact nut. 

A value between 2.5 and 8 kOm indicates that the spark plug is working well. If it is not, the plug should be replaced.

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