Caps and rotors

Distributor Cap and rotor:

The spark timing is taken care by the rotor spinning at the top. The secondary winding HT coil is connected to the rotor which spins inside the cap. The rotor spins past a number of contacts provided along the circumference of the cap. These contacts are arranged in firing order along the circumference. The contacts have a HT coil that supply high voltage electricity to the respective spark plugs.

Once the rotor comes in proximity to the contacts, a high voltage current generated in the ignition coil is supplied to the rotor. As the rotor and contact are in proximity, the high voltage current jumps across the gap and passes on to the respective spark plug. The high voltage current then generates spark at the tip of the spark plug, thereby initiating ignition in the respective cylinder. The rotor then spins away and moves to the next contact in firing order.

The contact points in the cap can wear out in time due to the repeated arcing between rotor and contacts. The electrical insulation of the HT coil can also wear out in time and needs to be replaced.

Inspecting the condition of the distributorcap and rotor. 

The distributor features a gray or brown plastic cap with metal terminals known as a distributor cap. The job of the distributor cap is to pass electricity through a series of wires in the correct firing order and at precise moments. When inspecting the cap and rotor look for the following : 1. cracked distributor, 2. corroded of dirty terminals, 3. carbon build-up inside the cap. Mostly it is not easy to see if a cap is broken except the fact that you could see some dark vanes on the inside of the outside of the cap. These are created by arcing of the voltage that runs through the cap. Cleaning of the inside of the cap and spray inside and outside of the cap with WD-40 could help for a short while but the cap will need to be replaced as soon as possible.