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How to Check Diesel Injectors

Updated July 20, 2017

Injectors are among the most important components of a diesel-powered vehicle. Bad injectors can make a vehicle decrease in power, accelerate or cause it to misfire or smoke. Checking for bad injectors yourself will save you a trip to a mechanic and the mechanic's fee.

Let the vehicle's engine idle until it warms up. The engine needs to run during the project.

Check the operating temperature of each cylinder using a digital pyrometer. A cylinder's operating temperature reading that is lower than the rest indicates that cylinder is faulty or weak.

Listen for a clicking noise from the injector. Place a long-shank screwdriver directly onto the injector, and hold the screwdriver handle up to your ear. If you cannot hear a clicking noise, then the injector is probably faulty or clogged.

Measure the resistance across the injector's terminals with a digital voltage OHM meter. If the resistance is not within your vehicle's specification, then the injector needs to be replaced. The specification can be found in your vehicle's manual.

Things You'll Need

  • Digital pyrometer
  • Long-shank screwdriver
  • Digital voltage OHM meter
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About the Author

Amanda Sargent lives and works on a cattle ranch near Bakersfield, Calif., where she owns quarter horses and cattle dogs. She specializes in animals, animal health and home-and-garden topics. Sargent also studies nursing and science at Taft College.