Distributor rotor for your car

Your Distributor rotor worn out? » Read more about common malfunctions • Repair • Replacement manual

As simple as it is important for the ignition: the rotor

The ignition distributor rotor is a small but very important component in older petrol engines. Indeed removing this small and very easy to disassemble part completely disables the engine. Yet, the ignition distributor rotor is no longer of any importance to modern engines.

Distributor rotor: position and function

The rotor sits under the distributor cap, fixed with two clamps or bolts. As soon as these are removed, the rotor can be pulled off. The distributor rotor is connected with the camshaft either directly or via a deflection gear. Its task is transmitting the ignition voltage from the ignition coil to the right spark plug at exactly at the right moment.

Distributor rotor: defects

Of all parts in a traditional ignition the distributor rotor has the most longevity. Its construction is simple as it is made of duroplastic and some conducting material, generally metal or brass. Nevertheless it can fail due to old age. A critical point is the contact point with the ignition cap. Every ignition causes a flashover with some material exchange, gradually scarring and shrinking the contact. The wear on the opposing contacts on the distribution cap is much more extensive. The correct repair is replacement of both cap and distribution rotor. The distribution rotor can also break for reasons of age or alternatively burn out as a cause of a massive ignition coil malfunction. These failures occur very rarely. A damaged ignition cap can cause problems. Penetrating moisture can also cause short circuit in the cap, which can damage the distribution rotor.

Repairing the distribution rotor

A breakdown of a distributor rotor as a separate component hardly ever happens. All components of this unit are very cheap and therefore they should all be replaced in case of any defect. This guarantees a new condition of the entire ignition. Repairing a single ignition distributor rotor is very simple: pull it off and replace it by a new component – done. Replacing a distributor cap is just as easy: the ignition cables are removed and inserted on the new cap in the same order. Subsequently it is fixed to its spot with the available clamps or bolts and the repair of this unit is done as well. Ideally the ignition cables are replaced consecutively in order to avoid swapping them, messing up the ignition order. Ultimately the spark plugs can be replaced one after the other. It is important that every component of the ignition system matches the engine. This especially applies to the spark plugs. If the length and the heat value of the spare parts do not match, serious damage to the engine can be the consequence.

Identifying ignition failure

A lot of work is saved by thoroughly examining an ignition failure or stalling of the engine before you start replacing components. If the car stalls during driving this does not automatically mean there is heavy damage. The most probable cause is that ignition cables between ignition coil and distributor have become loose. This is soon found out and repaired by a turn of the wrist, plugging the cable in its place. Alternatively the earth cable might have become loose from the battery or bodywork. In that case the car will stall as well as the ignition power circuit is interrupted. The earth cable can also be the cause of a car starting reluctantly. In this case removing the cable and thoroughly cleaning all contact points should do the trick. With a bit of pole grease added to the assembly, corrosion of the contact points is avoided. With these little measures you spare the ignition: fault currents, high resistance and bad insulation can damage the sensitive components around the distributor rotor and interrupter contact. By keeping the ignition clean at all times, the life span of all connected components is considerably extended as well.

Buying an ignition distributor rotor

Ignition distributor rotors are available at 2 EUR (± £1.80). The price of high-grade components will always be less than 15 EUR (± £13.50).