How to Test Spark Plug Wires
Check for symptoms., Inspect the wires., Run the engine., Use a jumper wire to ground a well-insulated screwdriver., Use a spray bottle with water to spray down the wires., Perform a spark plug wire resistance test., Inspect the spring clips that...
Step-by-Step Guide
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Step 1: Check for symptoms.
Defective spark plug wire leave tell-tale signs of their deterioration, including:
An erratic idle Engine misfire Radio interference Decreased fuel mileage Failed emissions tests due to elevated hydrocarbon emissions or a fault code indicating cylinder misfire.
Check engine light -
Step 2: Inspect the wires.
Use a flashlight or an area with good lighting to perform a visual inspection of the spark plug wires.
Look for physical damage to the wires or boots such as cuts and scorch marks.
Check the spark plug wire, and examine the insulation around the wire.
Look for damage due to high heat from the engine compartment (scorch marks).
Check for corrosion between the boot and the spark plug and coil. , Look for electrical arcs or listen for a snapping noise that may indicate a high-voltage electrical leak. , Drag the screwdriver down the length of each spark plug wire, around the coil, and the boots.
If you see an arc from a wire to the screwdriver, you have defective wire. , You will want to especially spray near the boots that attach to the spark plugs to see if any arcing occurs, and if mist is present.
If arcing is found at the boot near the spark plug, turn off the engine.
Then remove the boot from the plug and check inside the boot for carbon tracking.
If carbon tracking is present, the spark plug will also need to be replaced. , Locate the spark plug's resistance rating in the vehicle's factory service manual.
You can also search online for the resistance of after-market wires.
Use an ohm meter to determine if the resistance of the wire is in compliance with the recommendations.
Place the probes on either end of the wire lead, making sure they touch the metal contacts, and verify that they're within the range called for in the manual. , Damaged clips may allow the wires to slip and not hold their proper position. , Look in the vehicle's manual to help you with this task.
Cross coupling can create an energy drain. -
Step 3: Run the engine.
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Step 4: Use a jumper wire to ground a well-insulated screwdriver.
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Step 5: Use a spray bottle with water to spray down the wires.
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Step 6: Perform a spark plug wire resistance test.
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Step 7: Inspect the spring clips that hold the wires in the distributor cap.
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Step 8: Determine if your spark plug wires are routed properly.
Detailed Guide
Defective spark plug wire leave tell-tale signs of their deterioration, including:
An erratic idle Engine misfire Radio interference Decreased fuel mileage Failed emissions tests due to elevated hydrocarbon emissions or a fault code indicating cylinder misfire.
Check engine light
Use a flashlight or an area with good lighting to perform a visual inspection of the spark plug wires.
Look for physical damage to the wires or boots such as cuts and scorch marks.
Check the spark plug wire, and examine the insulation around the wire.
Look for damage due to high heat from the engine compartment (scorch marks).
Check for corrosion between the boot and the spark plug and coil. , Look for electrical arcs or listen for a snapping noise that may indicate a high-voltage electrical leak. , Drag the screwdriver down the length of each spark plug wire, around the coil, and the boots.
If you see an arc from a wire to the screwdriver, you have defective wire. , You will want to especially spray near the boots that attach to the spark plugs to see if any arcing occurs, and if mist is present.
If arcing is found at the boot near the spark plug, turn off the engine.
Then remove the boot from the plug and check inside the boot for carbon tracking.
If carbon tracking is present, the spark plug will also need to be replaced. , Locate the spark plug's resistance rating in the vehicle's factory service manual.
You can also search online for the resistance of after-market wires.
Use an ohm meter to determine if the resistance of the wire is in compliance with the recommendations.
Place the probes on either end of the wire lead, making sure they touch the metal contacts, and verify that they're within the range called for in the manual. , Damaged clips may allow the wires to slip and not hold their proper position. , Look in the vehicle's manual to help you with this task.
Cross coupling can create an energy drain.
About the Author
Andrew Harris
Andrew Harris specializes in lifestyle and practical guides and has been creating helpful content for over 7 years. Andrew is committed to helping readers learn new skills and improve their lives.
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