Don't get tempted to use the "shotgun" approach and try to fix everything at once. You're going to need to approach the problem with a little logic and patience. There are two separate paths to the ignition system, and both have to work properly before a spark can happen. You haven't told us if you're working with a 6 or 12 volt system, but with a few minor differences, the troubleshooting procedure is similar. First, be sure you have a well-charged battery that will crank the engine at normal speed. One that turns slowly due to a low battery can keep the ignition system from working, or give a very weak spark.
The low-voltage part of the ignition system, called the "primary" circuit, consists of the battery, the ignition switch, the primary winding of the coil, the points, and an electrical path back to the battery known as a "ground". The battery current must flow through all these parts in turn to produce magnetism in the coil to generate the high voltage needed to fire the spark plugs.
The high voltage system known as the "secondary" consists of part of the coil, the wire from the center of the coil to the distributor, the distributor cap and rotor, the spark plug wires, and finally, the spark plugs. The high voltage (10,000 to as much as 50,000 volts in some situations)across the spark plug gap is used to fire the fuel and air mixture in the cylinders. The primary and secondary circuits are completely separate, but both of them must function properly to make the ignition system work. (Confused yet?)
You'll need a voltage-testing device such as a probe-type test light or a voltmeter, but if you're an electrical newbie, stick with the test light. It's harder to make a mistake using it. Begin by taking the distributor cap off (Release the two spring clips on the side of the distributor) and while looking at the rotor, have someone spin the engine with the starter. The rotor should turn as the starter turns the engine. If that does not happen, you've got merchanical problems such as a stripped timing gear, broken distributor shaft, or some other mechanical disaster. If the rotor turns, we've eliminated mechanical failure. As the distributor is turning, the points should open and close. The gap between them will be small, about the thickness of two business cards stacked together, but it must be there. If the points do not open and close, loosen the adjusting screw on the point that's attached to the base plate, turn the engine by hand until the insulated block on the movable point is on the highest part of one of the six cam lobes, and adjust the gap until a feeler gauge blade about .016" thick will slip between the points. Snug the adjusting screw(s) down. Turn the ignition switch on and spin the engine, and see if the big wire at the center of the coil will jump a spark to the engine block or cylinder head by holding the wire about 1/2" from the engine. use some well-insulated pliers to hold the wire- - - - -you're dealing with a potential of several thousand volts. The distributor cap and rotor do not have to be reassembled to do this test- - - -just pull the center wire out of the cap and use it to test for spark. Obviously, leave it plugged into the coil. If adjusting the points gets the spark going, you've solved the "no spark" problem. Try this much of the process and get back to us with the results- - - -I don't want to overload you with information, and we're only about 1/10 of the way through a total ignition diagnosis!
Jerry
