| sawdustdad |
07-25-2014 08:20 AM |
Here's how I would diagnose no spark, in this sequence.
1. Make sure you have 12v+ at the positive side of the coil with the switch "on." Use test light/VOM from the Pos terminal to a good ground.
2. If yes, verify points closing. Remove wire to points from the neg side of the coil. test for continuity from the end of this wire to a good ground as you rotate the engine. at various points in rotation, you should alternately get continuity (zero ohms) and infinite ohms (open circuit) indicating that the points are opening and closing.
2a. If no 12v+ at the coil, go back to the ignition switch and look for power.
3. If you are getting continuity at the points (opening and closing) Check the coil. turn the ignition switch off and remove all wires from the coil. Use the VOM to test the resistance of the coil. should be about 8 ohms. Place the pos and neg leads of the VOM to the pos and neg terminals of the coil. If much less (6 or less) or infinite, you've got a bad coil. replace it.
3a. If you are not getting continuity across the points, check connections to and at the points. The wire to the points should be checked for continuity. Clean points with fine sandpaper and try the test again.
4. Check/replace the plug wire.
5. Check/replace the plug itself
6. Replace the condenser
Another test you can do is take a known good battery/jump pack and run a small wire from the 12v+ side of the jump pack to the pos terminal of the coil, clamp the neg lead to the engine's ground. Then touch the positive clamp momentarily to the start terminal of the starter. The engine should start and run. This is one way to rule out problems with your ignition circuit.
This is also another way to test run your engine w/o the rest of the wiring in place.
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