QUESTION: when starting 1980 spitfire car will start if i pull out the wire from the distributor cap and hold it 1/2 inch out, car will run . when I plug it in the car stops running. it. seems like the system is grounding out. please help.
ANSWER: Hi Jeff
When you pull the coil wire out away from the distributor cap and force the spark to jump to the cap, You have forced the coil to wait and build to a much higher voltage charge before the transfer of that charge to the secondary of the coil thus changing the voltage of the spark to increase a lot. This higher voltage now will jump the gap from the distributor rotor to the peg in the cap for each plug wire and then it can go down each plug wire (also resistor wire ) and then jump another gap at the spark plug.
The original Lucas coil normally only had about 25,000 to 35,000 volts to jump the two gaps and run down the resistor wires.
Your test of making the spark jump a large gap was a valid test of the system and you have found the area of the problem but not the exact problem.
Now you must narrow the problem to a smaller area or to the exact cause.
Here are the possible causes. I alway like to trace an electrical problem from the "Load" (spark plug in this case) back to source ( Igniter in the distributor )
First replace the spark plugs (be sure NOT to use "Resistor plugs")
Next, check the Ohms resistance on each wire. (should not be higher then about 4K ohms per foot of length) or replace the wires.
Next look closely at the inside and out side of the cap for carbon tracks.
Next, remove the coil wire from the cap and remove the cap and spin the engine like you did before but now try to jump a spark to the rotor itself with the coil wire. If you can jump a spark to the rotor, it is shorted and bad.
Next, check the ohms reading of the primary and the secondary windings of the coil. ( The specs are in your manual, if you don't have the specs let me know and I will dig and find them for you.)
Next, put your volt meter on a low DC volt scale and connect the positive test lead on the engine head on clean metal and the negative test lead on the negative post of the battery (not the cable end) Then have someone hit the starter and look for any voltage between the engine and the negative post of the battery. You do not want to see more then .5 volts.
If all that is good you probably have a bad igniter. The original Lucas / Opus ignitors were so prone to failure we had a hard time replacing them several times in one year. So many after market companies stated making their own ignitors. So you need to look to see what brand you have as the age of the car shows it most likely has an aftermarket ignitor in it.
Let me know,
---------- FOLLOW-UP ----------
QUESTION: CHANGED IGNITOR CHECKED ALL CONECTIONS,PROBLEM REMAINS THE SAME. ANY OTHER IDEAS.
Jeff, Why did you change the ignitor ? Didn't you test any of the items I suggested ? The ignitor is part of the "Primary" circuit. You have already established that the problem is most likely in hte "Secondary" Circuit. "Coil, Cap, rotor, wires, plugs or engine to body to battery ground.
When you have a spark jump it means the ignitor is switching the coil on and off and that is all it is suppose to do.
You will need a ohm meter to test the coil. If you don't have the specs let me know and I will look them up for you. But you will need to look on coil to see if it is a 12v coil or a lower voltage coil as some brands of ignitors use a 6v coil. You also need the ohm meter to test the wires.
Let me know.