The ignition distributor plays a pivotal role in the ignition system. Its basic functions start with triggering the firing of the ignition coil, controlling timing advance, and routing or distributing the coil’s high voltage output to each spark plugs.
In the case of older applications with breaker point ignition systems, the contact points are made to turn the ignition coil’s primary voltage on and off. This are mounted on a flexible plate in the distributor unit or housing. Cam lobes mounted on the distributor shaft turn against a plastic block on the breaker points to open and close the points. However in modern applications made with electronic ignition systems, the distributor has a magnetic pickup or Hall Effect switch instead of the old points to create a signal for the ignition module whose duty is switch off and on the coil. In most instances, the ignition module is found inside the distributor in the case of GM HEI brands and mounted on the distributor housing in the case of Ford TFI brand.
Distributors could wear out and cause a number of problems to your timing and or your engine
Normal wear in the distributor drive system can cause play that can affect timing, while worn components of the distributor like the shaft bushings can make your timing erratic. The primary cause of this bushings wearing out is irregular oil changes and varnish buildup on the shafts. These conditions could impact adversely on the performance of the engine, fuel consumption and emissions. This situation is best arrested with a replacement of the distributor.
In connection with timing, the distributor system on older applications is built with both a centrifugal advance mechanism and vacuum advance diaphragm. Components like flyweights and springs in the centrifugal advance mechanism increase timing advance as engine speeds up. Bushing wear, corrosion, weak or broken springs may influence the centrifugal advance mechanism to either over advance or retard timing. The solution to this could be lubricating the mechanism with high temperature dielectric grease and/or replacing weak or broken springs. However completely worn distributors require replacement.
ROTOR & CAP
The duty of the distributor rotor is to direct the ignition coil’s high voltage output to the various spark plug terminals in the distributor cap. However the condition of the cap and rotor must be given serious attention. This situation too applies to as the “air gap” or clearance between the tip of the rotor and cap terminals. Thus it becomes important to check that the cap or rotor that are cracked, worn, eroded or have carbon tracks are replaced.
Most times a distributor will break caps. This is usually caused by excessive end play in the distributor shaft. Much end play makes the rotor to push up against the cap and wear down the center button. This could eve cause a contact of the rotor with the terminals and damage or break the cap. Replacement is always recommended.
SEE ALSO:SIGNS OF A BAD DISTRIBUTOR CAP