To check your coil, ensure you have 12V going to the positive terminal. Once you confirm that is the case pull the wire out of the centre of the distributor and hold it a cm away from the distributor centre terminal. Have someone crank over the engine, and there should be a nice blue spark.. If it looks thin and a weak yellow, then the coil may be on its way out. You may wish to repeat this test and teh below test when hot an cold as on occasions issues may only appear when the coil warms up.
Voltmeter settings :
- With a volt meter Plug the black probe into the COM port on your multi meter,
- Plug the red probe into the VΩmA port.
- Switch on your multi meter, and set the dial to resistance mode.Resistance is measured in ohms, indicated by the Ω symbol.
- Most multi meters are not autoranging, meaning you will need to set the correct range for the resistance you expect to measure. If you’re not sure, start with the highest setting.
With all the wires taken off the terminals of the coil attach the positive and negative probes of the meter to first the negative terminal then the positive terminal on the coil. You should have a resistance reading of at least 3-4.5 ohms. A bad coil will show a higher reading then 3-4.5.
Next, place the red or black lead from the meter to the centre of the coil , and to either one of the terminals positive or negative. You want 9500-10000 Ohms, a little less is ok but no more. If it shows 10500 +, the coil needs to be replaced.
Repeat this test when the coil is both cold and worm from running as sometimes coils fail to work properly only when they are hot.