How to identify a faulty ignition distributor rotor

To diagnose the component, measure its working resistance. Connect the component to the electric circuit of the measuring bench, and connect an ohmmeter. For the contact ignition systems, normal resistance is 5-6 KOhm, and for contactless systems — 1 KOhm. The resistor should also be checked.

The rotor may be tested as follows: extract the center wire from the ignition distributor cap, then turn on the ignition, and hold the wire at a 3 mm distance from the contacts of the component. If a spark is observed at the moment of contact opening, the rotor is faulty.

After inspecting the component, make sure that no cracks are present, and check the contacts. Also check the clearance between the rotor and the carbon contact. If the clearance exceeds 1 mm, the carbon contact will burn out fast. The distance between the contacts of the component itself should not exceed 0.45 mm.

You may notice that the distributor rotor requires diagnostics by the following symptoms:

• the engine stalls abruptly;
• the engine misfires;
• the engine does not start at first attempt;
• the vehicle moves with jerks.

Reasons of the ignition distributor rotor malfunctions

The main reason of premature wear of the component is its poor quality. Oxidation of contacts of the distributor rotor during operation is a common phenomenon, same as carbon deposition. These defects are to be eliminated after every 10,000 km of mileage, otherwise this will decrease efficiency of the component and result in its complete malfunction.

A quite common fault of the distributor rotor is electrical breakdown. It occurs due to use of a restored component. Often the component is subject to breakdown, when cracks are present on the distributor cap, and condensed water is present under the cap.

Loss of integrity of the distributor cap wires and their breakage result in open electric circuit and failure of the component.

The component may melt on the surface due to an increased resistance and overheating of the resistor mounted inside it.

Replacing the ignition distributor rotor

This component is not subject to repair. To replace it, remove the distributor cap by removing the mounting nuts. Next, carefully (in order not to damage the contacts) extract the rotor by pulling it up, and install a new one in its place. While doing this, be extremely careful: if the guides are damaged, the entire ignition distributor will have to be replaced.