Join Date: Mar 2002
Location: Austin, TX, USA
Re: 6 volts at coil
9 volts is nominal voltage for a running motor. But with the points closed and the engine not running, 6 volts may be Ok. Personally its been a long time since I took that measurement, so I'd be tempted to overlook the 6 volt reading for now.
The wire from the firewall connector to the coil is a resistance wire. It serves the same purpose as a ballast resistor. It reduces ignition coil currents when the engine is running to prolong the life of the coil and prevent overheating. As you and Dale stated, the yellow wire from the solenoid will provide 12V while cranking for a hotter spark.
When the engine is running, the voltage on the coil primary will alternate between 12V (when the points are open) and a lower voltage (perhaps 6 volts) when the points are closed. When the engine is running, the voltage on the coil (+) will show a DC reading of Vmin + (Vmax - Vmin) * (1 - Dwell). So if Vmax is 12 volts, Vmin is 6 volts, and the dwell is 30, then the reading on the coil (+) will be 6 + 6*.70 or 10.2 volts... in the ball park of 9 volts.
Long story short, I don't think a 9volt reading on the coil (+) is typical for a non-running motor with the points closed. Perhaps someone with a breaker point setup could measure the coil (+) voltage on a non running motor with the points closed and confirm or correct my statements.
The neutral safety switch only affects engagement of the starter solenoid. If the engine cranks the NSS is ok.
Beware also, that these carberated engines are touchy. If you do in fact have some sort of an igniton problem, you can quickly wind up with a flooded motor which compounds the no start issue.
68 Coupe, 350 w/ Edelbrock Performer RPM heads, cam, intake, 700R4, Dave's small body HEI
Last edited by dnult; Nov 27th, 08 at 10:34 PM.