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Troubleshooting the ignition system in your S-10 Blazer begins with a basic understanding of how the system works. Electrical power is supplied to the primary coil of your ignition coil by the ignition module, generating a magnetic field around the secondary coil in the ignition coil. At a specific point (ignition timing) in the engine rotation, the power is turned off to the coil. When this happens, the magnetic field collapses around the secondary coil and induces a voltage spike in the secondary coil. This voltage travels out of the coil wire and to the distributor cap, or the spark plug on a distributor-less ignition system, and ignites the air/fuel mixture.
Step 1
Check for power at the primary coil circuit using the automotive circuit tester. Attach the black (negative) and red (positive) clips on the tester to the battery. Turn the key to the "Run" position and touch the probe end of the tester to the two wires on the coil by inserting the probe into the back of the electrical connector. This is called back-probing. Turn the ignition key to the "Start" position and watch the light on the tester. Both wires should show power. If no power is present, replace the brown fusible link on the back of the Blazer’s starter. If power is shown on one wire and ground is shown on the other wire, replace the coil.
Step 2
Remove the electrical connector from the coil and back-probe the ground wire. Turn the ignition key to the "Start" position and watch the tester. It should indicate a flashing ground signal. If no flashing ground signal is indicated, replace the ignition module and pick-up coil in the Chevy’s distributor.
Step 3
Remove the coil wire from the coil, and hold the 12-volt test light close to, but not touching, the secondary coil tower that the coil wire was plugged into. Turn the ignition to the "Start" position and watch the coil. A bright spark should jump from the coil tower to the test light. A good ignition spark can produce a spark that can travel more than an inch to the test light. If the spark is weak or doesn’t happen, replace the coil.
Remove the plug wire from a spark plug, leaving it attached to the distributor cap (or coil pack on S-10s with distributor-less ignition systems) and turn the ignition key to the "Start" position. A bright spark should cross an inch or more to the engine block. If there is no spark present or a weak spark, replace the distributor cap, rotor and plug wires.
Items you will need
- Automotive circuit tester
- 12-volt test light
