The distributor rotor and cap pass voltage from ignition coils into the engine’s cylinders. From here, the air/fuel mixture is ignited and powers the engine. The coil connects to the rotor and the rotor rotates inside of the distributor cap. When the tip of the rotor passes a contact on the cylinder, the high voltage pulse goes from the coil to the cylinder through the rotor. From there, the pulse moves from the gap an onto the spark plug wire, where it eventually ignites the spark plug on the cylinder.

The distributor rotor and cab are subjected to high voltage on a regular basis, meaning every time you turn on your vehicle, electricity flows through them. Because of this, they do wear out from time to time. When the distributor rotor and cap are replaced, the entire ignition should be inspected to ensure everything else is in good working condition.

Preventative maintenance is key to catching your distributor rotor and cap failing. Every time your vehicle has routine maintenance or is serviced by a professional, the ignition should be thoroughly inspected. In addition, this part is more likely to fail if you drive through a deep puddle because water will get into the distributor cap and short out the electrical current. The cap may not need to be replaced if this is the case, it may need to just dry out for a certain period of time. If you are unsure or if you start to notice any problems with your vehicle starting up, you can always schedule an inspection from a professional mechanic. They will thoroughly inspect your system and replace the distributor rotor and cap.

Since the distributor rotor and cap can go bad over time because they are located in a harsh environment, it is important to know the symptoms this part will give off before it completely fails.

Signs you need your distributor rotor and cap replaced include:

  • The Check Engine Light comes on
  • The car does not start at all
  • The engine misfires and has trouble starting

The distributor cap and rotor is an essential part to starting your vehicle, so the repair should not be put off.

This article originally appeared on YourMechanic.com as How Long Does a Distributor Rotor and Cap Last? and was authored by Valerie Johnston.


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