Isuzu Cars and Trucks 1981-1991

Electronic Ignition


general Information
System Operation
Except 2.8L engine

There are 2 types of ignition systems used on Isuzu engines: one uses a conventional centrifugal advance type distributor and the other uses a fully transistorized type distributor.

Conventional type distributors are made up of the distributor shaft, rotor shaft, rotor head, breaker assembly, reluctor, governor flyweight, pinion gear and vacuum control unit.

Transistorized distributors consist of dust brushing, rotor, pinion and a crank angle sensor built into the distributor housing. The crank angle sensor uses a photo-electric pick-up to measure piston position and engine speed.

v6 engine

The computer controlled Electronic Spark Timing (EST) ignition system used on the V6 engines consists of the battery, distributor, engine control switch, spark plugs, primary and secondary wiring.

the computer, or Electronic Control Module (ECM), monitors the information from the engine sensor network. The ECM uses this information to calculate the proper spark timing and tell the distributor when to make timing modifications.

The distributor dies not have centrifugal advance weights, springs or a vacuum advance unit.

The V6 engine is equipped with Electronic Spark Control (ESC) The heart of the ESC systems is the knock sensor which is mounted on the engine block. The knock sensor is connected to the electronic spark control module which is located on the right fender panel in the engine compartment or on a bracket mounted to the block. In response to engine knock, the sensor transmits a signal to the electronic spark module ('"half function box"). the spark control module sends the signal to the ECM which in turn tells the distributor to retard the spark timing up to 20and#x00B0; to reduce spark knock in the engine.

For further information pertaining to the electronic ignition systems, refer to .

air gap setting

On the G200Z and 4ZD1 engines, the air gap setting in the distributor should be checked and adjusted before the ignition timing is adjusted.

  1. Remove the distributor cap, O-ring and rotor.
  3. Use a feeler gauge to measure the air gap at the pick up coil projection. The gap should be 0.008 and 190.016 in. (0.20 and 190.40mm) for the G200Z engine, or 0.012 and 190.020 in. (0.30-0.50mm) for the 4ZD1 engine; adjust it if necessary.

The electrical parts in the system are not repairable. If found to be defective, they must be replaced.

Click image to see an enlarged view

Fig. Air gap setting G200Z and 4ZD1 engines