The ignition coil on your Chevy car or light truck provides the spark energy to fire the compressed air and fuel mixture in the engine's combustion chamber. The design of the ignition coil that Chevy uses has changed over the years, but the theory and concept have stayed the same. Current is passed through a primary coil of wire, and a magnetic field develops around the coil of wire. The current is turned off and the magnetic field collapses. The collapsing magnetic field induces high voltage into the secondary coil winding, and that voltage travels down the coil/plug wire and fires the spark plug.
Test for power and ground at the coil during cranking. If power is found on one side of the electrical connector on the coil during cranking, and flashing ground is found on the other side, this indicates an open coil. Replace the coil to repair. If power is present on both sides of the electrical connector, the coil primary winding is not open, but may be shorted. If no power is present at the coil electrical connector, check for blown fuses, or burned fusible links. The locations of these can be found in the service manual for your specific Chevy vehicle.
Remove the coil electrical connector and the coil wire. Attach the test leads from the digital volt/ohm meter to the pins in the coil where the electrical connector attaches to test the primary winding for resistance. Set the meter for ohms and compare the reading on the meter to the factory specifications in the service manual. Resistance specifications vary, so consult the service manual for the specifications for your specific vehicle. Replace the coil if the resistance is out of the range of the specifications.
Test the secondary for resistance by attaching the leads from the meter to the coil wire connector on the coil and the metal body of the coil. Any resistance reading during this test indicates a shorted coil. Replace the coil if the resistance during this test shows anything but an open circuit.
