What can result from open or high resistance spark plug wires?
An open plug wire or spark plug may cause the firing voltage for that cylinder to spike to the coil’s maximum output. If you see a higher than normal firing voltage for a particular cylinder, turn the engine off and measure the plug wire’s resistance end to end with an ohmmeter.
What is the resistance of a good spark plug?
Serviceable Spark Plug Resistance To help assure reliable and trouble free operations, Tempest recommends replacing spark plugs in service having a resistance value of more than 5000 ohms (5k ohms) or less than 500 (0.5k ohms). For new plugs, we recommend 4000 ohms as the maximum acceptable value.
What causes a spark plug to go bad?
Vibration damage – Constant wear and tear caused by engine vibration can loosen the electrical connection at the spark plug. This causes an increase in the voltage required to fire the spark plug, which could damage the ignition coil as well as the spark plug wires. Heat damage – Engine heat can burn wire insulation and boots.
How to test the resistance of spark plugs?
Testing Spark Plug Wires Resistance. With this test, you’ll check the condition of the conductor that runs through the thick insulation of your spark plug wires. For this test, use a simple analog or digital ohmmeter. Set your meter to the ohms scale and to a setting that will let you read 50,000 ohms or above.
What kind of voltage does a spark plug have?
It carries the high voltage (30k to 50k volts) produced by the ignition coil to the spark plug. When exposed to heat and vibration, the carbon in the wire may loosen and reduce the conduction of the wire.
What causes a spark plug to jump to the ground?
Heat damage – Engine heat can burn wire insulation and boots. A damaged boot can impede proper spark plug wire seating and performance. Wire insulation that’s damaged by head can allow voltage to jump to the ground rather than jumping the gap at the bottom of the spark plug.
What happens if a spark plug has too much resistance?
Too much resistance in the wire leads to less electrical current getting to the plug. Reduced electricity results in not enough spark to ignite the gasoline mixture that fires the engine.
How can you tell if a spark plug is bad?
When the spark plug wire is bad, it will cause an erratic flow of electrical current to the engine. Next signs of bad spark plug wires are slow acceleration. A poor acceleration is a quick way to tell you that the spark plug wire is faulty. All you need to is to change the spark plug.
How many ohms does a spark plug wire have?
The resistance of many wires is measured in ohms per foot. A wire with high resistance can be in the 5000 ohms per foot range for especially high-output ignition systems, whereas a low resistance performance wire could easily get double digit ohms per foot.
Can a bad spark plug wire cause a misfire?
If this is where your misfire is most pronounced then its a safe bet to change the wires. The higher voltage produced on initial acceleration will find any internal breakage and cause the misfire. 1500-2000 ohms per foot of cable is usually present, even on a bad spark plug wire, the misfire happens on the higher voltage.