See Figures 1, 2, 3 and 4
Electronic ignition was optional in 1972-73 and became standard in 1974. This unit functions basically the same as a breaker point distributor, although the parts used are different.
The distributor housing, cap, rotor and advance are the same on the conventional distributor and both systems use the same spark plugs and ignition coil. A magnetic pickup and a control (reluctor) have replaced the breaker points and the rotor. A condenser is no longer necessary. The only maintenance required on electronic ignition units is the inspection of the wiring and the cleaning and changing of the spark plugs.
Also, as a result of the elimination of the contact points, the dwell on electronic ignition units is non-adjustable. It can be read on a dwell meter but cannot be adjusted.
The magnetic pick-up and control unit have replaced the functions of the contact points and, unlike the contact points, normally show no sings of wear. Therefore, periodic checks of dwell are unnecessary, and the dwell cannot be altered anyway.
There is however, an adjusting slot on the distributor plate that is used to change the air gap between the reluctor teeth and the pole piece of the coil. Unlike breaker points, reducing the air gap will not retard the timing and since dwell is determined by the control unit and is independent of the pick-up unit, changing the air gap will not affect timing or dwell. The gap between the pick-up and the reluctor should be properly set however.
One of the main advantages of the electronic ignition system is improved starting because with no points, the possibility of arcing across the points has been eliminated. However, a pick-up gap that is too wide can cause starting problems. A "no-start" condition can exist if the gap is too wide.
If you encounter a hard staring condition, don't immediately blame the pick-up gap and change the adjustment. The entire system should be left alone except as a last resort. Make sure that the fuel system and the rest of the ignition system are performing satisfactorily. Although setting the pick-up gap correctly is a must when installing a new reluctor or pick-up unit, the gap does not change in service (due to wear) and should not require periodic checking or adjustment. The main reason that the minimum air gap specification exists is to make sure that the reluctor does not contact the pole piece as the vacuum plate moves.
When checking the pick-up gap, use a non-magnetic feeler gauge. This is because a feeler blade that is attracted to the magnetism of the pole piece will give a false feel or drag. If non-magnetic feeler blades are not available, use brass shim stock of the proper thickness.
When working on a van with electronic ignition, be careful not to touch the round transistor located in the control unit heat sink when the ignition is on. It can give out a very large shock.