[Mgs] 78 B fires right up and dies

The Roxter rocknatural at gmail.com
Mon Oct 1 10:17:04 MDT 2007


Blair J. Weiss wrote:
> List,
> I am having another (probably simple) problem...
>
> Turn the key, the motor fires right up. Return the key from start to 
> regular, engine dies. If I hold the key in the start position, the motor 
> will run (and so does the starter motor)... trust me I know the difference 
> between really running and just kinda running along with the starter 
> engaged...
>
> I don't have a schematic handy and I don't have a second person to turn the 
> key while I check voltages... Are there two different contacts on the 
> starter switch, one on the regular on position and another on the start 
> position... could I just have dirty contacts or does this seem like 
> something else?
I'm guessing you have a 9 volt coil. This was an design that was supposed to make starting easier, since it provided full coil voltage while starting, but put a resistor in the ignition circuit when running. 

I'm guessing the resistor has burned out or the connections to it have gone open, so the straight circuit provides voltage to the ignition when starting, but provides none when running. Some BMC cars use an actual resistor, but others use a length of resistor wire, usually pink.

You can use a wire with alligator clips to bypass the resistor, but it will provide too much voltage to the ignition circuit and might possibly eventually damage the coil.

I prefer to use a 12 volt coil and bypass the resistor, since even though the drain from the starter will draw down the ignition voltage to around 9 volts, if everything is in good shape, it will start just fine.

-The Roxter
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