Talk Morgan Forums Morgan Sports Cars Maintenance & Servicing 1999 3.9 v8 ignition query

Hi
Do any of you guys out there why? The black wire to the coil has +12v when I switch on the ignition - no issues with the ignition system just strange and a bit unerring as all black conductors always return to earth
Ta
Alan

Assuming this is a conventional points/distributor system:
Don’t know whether you are referring to the wire that feeds coil from ignition switch or the wire that goes from coil to points. If it is the latter, the wire could well be black as it will be “earthy” each time points close. If points happen to be open at moment of measuring voltage then the black wire will be floating at +12 volts with respect to earth, as will the other incoming wire.

The wire becomes live when disconnected from the coil and the ignition switch is turned on

May seem odd Alan but with ignition on and engine not running BOTH sides of ignition coil will measure battery volts or close, IF points happen to be open hence no circuit through coil. Your voltmeter is a high impedance device so would not load the circuit to any degree. Could well be that with electronic ignition the coil remains open circuit until engine is turning over so same measurements will apply.

Cable from coil (CB) to distributor points (or equivalent) should be white/black BTW. It's not a permanent ground connection.

If the black wire is on the + side of the coil, which is the 12 volt power to the coil, it is likely to be the 12v feed from the immobiliser. From the age of you +8 I guess it will have an immobiliser. For +8 without an immobiliser the power is via a white wire which may have a green tracer.

(My experience is that often on security modules all the wires are black to make life difficult)

There is, or should be, another wire from that same terminal on the coil which is white and goes to provide 12v power to the ignition module

Mike

Hi
Mike has hit the nail on the head . The wire in question comes from the Spider Unit where all wires are black query now solved after half a day tracine and testing - thanks all
Alan