Topic: Troubleshooting Ignition Systems

No Start Condition

No matter what DIS system your customer is trying to service the following basic pinpoint tests should be performed before any parts are replaced. The first test is to verify the complaint by checking for a spark. The next test involves, testing the power and ground circuits for the DIS module. If you have no spark, and the power and ground circuits are OK you should test the coils for opens or shorts. If they test good check to see if a reference signal is being produced by the module, if not, check the crankshaft sensor input signal at the DIS module. If the signal is present and has the correct frequency (engine cranking speed) and amplitude (voltage strength) the module has probably failed. Let's take a closer look at these steps one at a time.

Testing For Spark

Diagnostic Process Step #1

Testing For Spark Disconnect tachometer wire (if equipped). A shorted tachometer can prevent the vehicle from starting. Disconnect the camshaft position sensor (if equipped). A shorted signal can fool the module and prevent the engine from starting. Attempt to start the engine. If it starts, your problem is with the sensor or tachometer. Using a spark tester (GT-1) check for an adequate spark. Install the tester on plug wires #1, #3, and #5 (V6) one at a time. Leave the matching plug wire attached while testing for a spark.

Voltage Testing

Diagnostic Process Step #2

Test Coil Power & Ground Source Turn the ignition switch on. Check for battery voltage at the ignition positive circuit that feeds the ignition control module. No voltage present. Check for a blown ignition fuse or open circuit between the fuse and the module. Test ground circuit for resistance to negative battery post (0 ohms). High resistance present. Repair an open or poor connection in the ground circuit.