GM Lumina/Silhouette/Transport APVs 1990-1999 Repair Guide

Diagnosis and Testing

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SECONDARY SPARK TEST



It is imperative to check the secondary ignition circuit first. If the secondary circuit checks out properly, then the engine condition is probably not the fault of the ignition system. To check the secondary ignition system, perform a simple spark test.

  1. Remove one of the plug wires and insert some sort of extension in the plug socket. An old spark plug with the ground electrode removed makes a good extension.
  2.  
  3. Hold the wire and extension about 1 / 4 in. (0.25mm) away from the block and crank the engine.
  4.  
  5. If a normal spark occurs, then the problem is most likely not in the ignition system. Check for fuel system problems, or fouled spark plugs.
  6.  
  7. If, however, there is no spark or a weak spark, then test the ignition coil and the camshaft and crankshaft position sensors. For testing the camshaft and crankshaft position sensors, refer to Driveability and Emission Controls .
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