I'm working on an early 80's Ford sedan with an inline 6, and single barrel carb. The engine is turning over, but not firing. I'm not getting any spark from the coil - due to the fact that the negative terminal has a constant ground. The positive terminal has 12 volts (as it should). It's a single pickup distributor. There's a detached ignition control unit mounted to the firewall. There are three wires leading from the ignition module to the distributor. It looks like one is ground while the other two go to the magnetic pickup. When I disconnect the distributor from the ignition module, the negative terminal of the coil is no longer grounded.
Does this indicate a bad magnetic pickup in the distributor? What test can I do to determnine if it's the distributor or the ignition control?