Subaru Coupes/Sedans/Wagons 1985-1996 Repair Guide

Diagnosis and Testing


Fault diagnosis of the electronic ignition system is carried out via the fuel injection control unit. See Electronic Engine Controls in Driveability & Emissions Controls for further information.


Carbon Point

See Figure 1

Click image to see an enlarged view

Fig. Fig. 1: Measure the carbon point

Measure the length of the carbon point in the distributor cap. Standard length should be 0.49-0.47 in. (10-12mm). If not within specification, replace the carbon point.

Distributor Cap and Rotor

See Figures 2, 3 and 4

Click image to see an enlarged view

Fig. Fig. 2: Inspect the vent holes in the distributor base and cap

Click image to see an enlarged view

Fig. Fig. 3: Use a vacuum pump to check the plunger

Click image to see an enlarged view

Fig. Fig. 4: Measure the signal generator resistance

  1. Inspect the distributor cap for any breather hole clogging, electrode cracks or damage, center carbon wear or weak spring action. Check the rotor for cracks and damage.
  3. Measure the insulation resistance of the cap and rotor. Resistance should be 50,000 ohms or more. If not, replace the cap and rotor.
  5. Check that the vacuum canister plunger actuates when vacuum is applied using a hand vacuum pump.
  7. Using an ohmmeter, check the signal generator. Connect the ohmmeter leads to the wiring harness. Resistance should be 130-190 ohms. Move a screwdriver close to and away from the coil iron core. The tester needle should deflect. If the signal generator fails any test, replace it.