I am having trouble diagnosing a problem with a distributor. The ignition system is a standard 12 Volt system with points, condenser, rotor, etc. The problem manifests itself in a lack of spark from the secondary coil output to the rotor. The engine is a Hercules KLM Flathead 6 out of a 1957 Chris Craft. However, the ignition system appears to be identical to my 1953 F100 Ford Flathead V8 except for the fact that the Hercules is a 12 Volt negative ground.

When the points are closed, the electrical path from the output of the primary coil goes through the distributor wall, through the points and directly to ground, as it should through the closed points. However, when the points are manually opened, this circuit is still going directly to ground. Thus, the system acts as if the points are always closed and produces no spark from the coil output. Evidently, there is a ground path around the points.

I suspect that perhaps one of the insulators where the primary wire attaches to and passes through the wall the of the distributor has broken down, allowing direct contact with the distributor body. However, a cursory look at the insulators between the coil terminal and the distributor body doesn’t show an obvious failure of an insulator. I have not yet disassembled the connection to the distributor to get a good look at the insulators. If anyone has any ideas of where else to look, I would appreciate your thoughts. Thanks.

 

I would disconnect the primary wire from the points and the coil and check with an ohmmeter if it still shows the primary wire shorted to ground. If you have infinite resistance, then your primary wire feed thru insulators are probably good so next it could be a shorted condenser so use the ohmeter to see if you have a low resistance between the condenser wire to ground while it's disconnected from the points. If all OK there look for any problems with bare or cracked insulation on the wire that goes between the points connection stud and the insulated feed through wire inside the distributor.
If you find that the insulated feed through connection is a problem and you can't find the parts to fix it. NAPA, Autozone, O'REILLY, carry primary wires with a formed rubber boot that should fit in the hole of the distributor wall and that will replace the insulators and feed through bolt.

 

have you checked the condenser? It could be your short to ground.

 

Thanks for the ideas. I will pursue them tomorrow.