Points for distributor care

Press, 30 November 1978, Page 18

Points for distributor care

| Motoring

Last week we dealt with spark-plug care, and how it can help the home mechanic get better fuel economy and longer engine life with just a little work in the home garage. This week the care of the distributor and the replacment of contactbreaker points sets will be outlined.

The distributor acts as a switch to control the current from the coil’s highvoltage primary winding. It distributes the coil’s high-voltage output to the spark-plugs in the required firing order by means of the rotor-arm. The contact-breaker is connected to the low-volt-age circuit in the car’s ignition system and when the contact-breaker points are open this stops cur-

rent from flowing in the coil’s primary circuit and collapses the magnetic field in the coil, producing the 15,000 to 30,000 volts needed to send a spark from one spark-plug electrode to the other.

Because the whole ignition system is dependent on the correct functioning of the distributor, and especially the contact-break-er, it is important to keep these items of equipment well maintained. The distributor should be checked every 5000 km. Label the spark-plug leads so they will be replaced in the right order then remove them from the plugs, wiping the insides of the plug-caps W’ith a dry coth. Unplug the high-tension lead from the coil, then

unclip the distributor cap and lift it off. The central carbon brush on the inside of the cap should move freely, and the inside of the cap can be cleaned with a rag moistened with a little petrol. Remove the rotor arm, which should pull off.

The distributor’s centrifugal timing mechanism can be lubricated by applying a few’ drops of light oil in the space alongside the central cam. Grease the face of the cam lightly and put a drop of oil oh the moving-contact point’s pivot post. If there is a felt or sponge pad under the rotor arm. oil it.

The condenser is included in the distributor to prevent excessive arcing, and if a new set of points burns out quickly the condenser may be faulty, if its earthing and connection are found to be good. However, condenders seldom fail and, anyway, their replacement is quite simple.

If a fault in the distributor’s timing mechanism is suspected, the distributor plate should be taken off by removing the two screws holding it to the body of the distributor. Disconnect the vacuumadvance.

When the plate is removed the centrifugal weights will be revealed, and these should be checked for obstructions. Both springs should be connected to their retaining pins.

Another useful routine is to check the vacuum lead, which is usually a thin metal or plastic pipe leading from the car’s inlet manifold. Check that the pipe is not kinked or disconnected. The distributor contactbreaker has two metal points — one fixed and

the other sprung so that it opens and closes as the distributor cam revolves. The movable point is insulated and the fixed end of the spring which carries it makes contact with an insulated terminal on the distributor case. Every 10,000 km the contacts should be inspected. If the points are pitted or burnt they should be replaced — it is inadvisable to clean them with a file except as a stop-gap measure.

Most cars nowadays are fitted with a one-piece contact points set, an innovation which has greatly simplified the job of replacing the points.

Remove the rotor arm, and if unsure about reassembly it may prove handy to draw a simple diagram of the distributor, showing the position of the various parts. Remove the old one-piece contact set, taking care to note the order in which the leads are connected. Remove any grease on the contact faces of the new contact set by wiping then remove the ’ nut on the plastic bush and place the new set in position. Replace the clamping

screw with its washers in correct order. Reconnect the low-ten-sion lead and condenser lead on to the plastic bush. Screw the nut on to the plastic bush, taking care not to overtighten. Now the points are ready to be set.

Turn over the engine by hand, with the ignition off, until the shoe of the

moving point is on the peak of one cam — the points should now be fully open. Check the gap with a feeler gauge. The gap will be specified in the car’s handbook.

To adjust the points, loosen the securing screw, which should be the largest screw on the distributor plate, and move the contact-breaker baseplate with a screwdriver until the points just touch a feeler inserted between them.

Tighten the screw and recheck the gap. Then oil the pivot-post lightly, taking care to get no oil on the points. Smear a little light grease on the cam.

Replace the rotor arm. coil-lead and spark-plug leads and test-run the motor.