QuestionHi Ihave a 77mgb with a 74 ignition system.. no spark at coil when cranked.. the coil is new,,,when ignition is on 12.4 volts @ coil discoonected.. 11.5 vdc when connected.coil gets warm when connected.thanks for any help or suggestions
AnswerHi Jim,
Do you mean you have points in the distributor? If so you need to do a couple of tests.
Remove the dist. cap and rotor and look at the points and rotate the engine until the cam opens the points. Check the point gap (.015")
Now, turn the ignition key to "ON" (not start) With your volt meter check the voltage on both sides of the coil. Should be 12.4v on BOTH sides of the coil when the points are open.
If you have 12.4v on one side and little to none on the other. Turn the ignition off and remove the points spring off of the post in the distributor. Be sure to put a plastic hat shaped insulator on the post first, then the points spring, next put the condenser lead and the pig-tail wire against the points spring. Now place the second hat shaped insulator on the post so the hat goes into the two leads and into the points spring. Now you can put the nut and (washer if it has one)on to the post.
It is important that the points spring, the pig tail wire and the condenser wire must not have any contact with the post they are mounted on. That is why they have the hat shaped insulators.
Now check the voltage on both sides of the coil. You should have voltage on both sides of the coil. Now rotate the engine until the points are closed and check voltage at the two post of the coil. you should have voltage on only one side and it should be the side with the white wire/s on it. The side with the white w/black tracers should have little to no voltage.
Next, turn off the ignition and disconnect either side of the coil and set your volt meter to a low ohms scale and check across the two posts of the coil. It should be 2 to 3.5 ohms. If it is a 1.5 ohm coil you need an external ballast resistor to use that coil.
Let me know,
Howard
