Content

• Method 2 of 3: Inspect the wires with the motor on
• Method 3 of 3: Check the wires with a tester
• Tips
• Warnings
• What do you need

1 Look for physical damage to the wires or lugs, such as cuts or scorching spots. Shine a flashlight on them or work in a better light area to visually inspect the spark plug wires and rubber cap. A row of wires runs from the cylinder head to the distributor or ignition coils. Inspect the insulation around the spark plug wires.

• Marks indicate damage due to high engine compartment temperatures.

2 Check for corrosion between the rubber tip, spark plugs and coil. Disconnect the tip from the spark plug and inspect the connection. Check for stains or damage. Then unscrew the spark plug and inspect the bottom for stains or damage.

3 Inspect the spring clips that hold the wires in the distributor cap. Follow the wires from the cylinder head to the distributor. Tug on the end of the wire to make sure the clips are holding the top of the spark plug securely. If the clamps are intact, they should provide a secure connection between the wire and the spark plug.

• Damaged clips may cause the wire to slip out and end up in a different location.

Method 2 of 3: Inspect the wires with the motor on

1. 1 Determine the symptoms of a defective spark plug wire. A defective spark plug wire can be identified by its characteristic signs of wear, such as:
   • unstable idle;
   • engine misfire;
   • radio interference;
   • higher fuel consumption;
   • Failure of the emission test due to high hydrocarbon content or malfunction due to a misfire in the cylinder block;
   • flashing engine light.
2. 2 Perform a visual inspection with the engine running. Sometimes a problem can be detected simply by looking at the engine. Check for electrical discharges near the spark plug wires. Also, listen for strange clicking sounds that may indicate an electrical leak.
   • Ask a friend to start the engine while you inspect it. Pay attention to any abnormalities such as sparks or smoke.
3. 3 Use a screwdriver to check the insulation of the wires. Take a wire long enough to run from the ground electrode to the spark plug. Wind one end of the wire around the shaft of a well-insulated screwdriver and the other end to a grounding conductor. Then run the tip of a screwdriver along each spark plug wire, around the coil and lugs. If you notice an arc from the wire to the screwdriver, then the wire is faulty.
   • Be sure to use a well insulated screwdriver. Otherwise, you may get an electric shock.
4. 4 Spray water on the spark plug to see if it shorts. Fill a spray bottle with water and spray along the wires. Spray water near the protective tips and watch for sparks. If the tip near the spark plug suddenly sparks, turn off the engine and carefully inspect the tip.
5. 5 Examine the inside of the handpiece for traces of soot. If, after spraying water, the spark plug starts to spark, then you need to look at the inside of the tip. Remove the candle cap by pulling it up and out. Examine the tip for traces of soot - black marks on the inside of the tip. These marks indicate that the connection is not perfect and can therefore lead to ignition misfires.
   • If traces of soot are present, the spark plug and wire must be replaced.

Method 3 of 3: Check the wires with a tester

1. 1 Find the rated resistance of the spark plugs. Usually it is indicated in the vehicle manual. If you do not have one, download the electronic version of the manual from the Internet.
   • If you do not have a manual for the car or the car does not have factory wiring, look for the necessary information on the Internet. Enter the make, model and year of manufacture of the car in the search engine, and the words "rated power of resistance of the spark plugs" (without quotes).
2. 2 Use an ohmmeter to determine the resistance of the wires to find out if it meets the recommended value. Disconnect the wire from the engine by removing the tip from the spark plug and unscrewing the wire at the other end. Place sensors on both ends of the wire. They should touch metal contacts.
   • Make sure that the resistance is within the range stipulated by the vehicle's owner's manual.
3. 3 Determine if the spark plug wires are positioned correctly. Look at the spark plug layout in the vehicle owner's manual. Trace each wire from the connection on the engine block to the corresponding spark plug. Each wire must go to a specific spark plug.
   • This problem could occur if you changed the spark plugs or fitted the tips in the wrong order.
   • Cross-connect can lead to current leakage and motor malfunction.

Tips

• Some engines have ignition with an individual coil on each spark plug that bypasses the spark plug wires, although rubber lugs are still present.
• Keep spark plug wires clean to avoid loss of conductivity.
• Cross-connect is not always a bad sign. Some manufacturers try to eliminate magnetic fields in this way.

Warnings

• If you have a pacemaker or similar device, do not test the spark plug wires yourself, as accidental electric shock may affect the operation of the device. Better to contact an auto mechanic who will do the job for you.

What do you need

• Torch
• Wire jumper
• Insulated screwdriver
• Ohmmeter