On Tue, 2 Apr 1996, W. R. Gibbons wrote:
> On Tue, 2 Apr 1996, David E. Brown wrote:
>
> > when I did see some spark at the plug. At this point, with a new
> > coil and ballast resistor, I have no spark even from the coil lead
> > to ground, but the coil primary (switch side) has power. I don't
> > get it.
>
> Part of this should be easy to trouble shoot. You have a new coil, and
> power to the coil primary. If the coil is good and has power, then you
> have to have a fault in the circuit through the points. This circuit
> makes a circuit through the coil primary to ground when the points close
> and disconnects the circuit when the points open. The changing voltage
> in the primary induces a higher voltage in the secondary. If no current
> flows through the primary, or if it always flows through the primary,
> there will be no spark.
>
> Disconnect the lead from the coil to the points. Take a jumper wire,
> attach it to the points side of the coil primary. With the ignition on,
> and power to the other side of the primary, momentarily ground the other
> end of the jumper wire to the chassis. Have an assistant hold the coil
> center wire an eighth inch from ground and look for a spark. If no spark,
> your new coil is faulty.
>
> If you do get a spark that way, I would bet either your points are not
> opening, your condensor is shot, or there's a permanent short to ground,
> or a permanently open circuit (for example, oxidized points) in the circuit
> that goes through the distributor, the points, and to ground.
>
> It should be fairly easy to check all these possibilities.
>
> Ray Gibbons Dept. of Molecular Physiology & Biophysics
> Univ. of Vermont College of Medicine, Burlington, VT
> gibbons@northpole.med.uvm.edu (802) 656-8910
>
>
My 79 B w/electronic ignition had a similar problem - spark coming from
the coil (as verified by holding the coil wire close to the block), but
no spark to the plugs - problem turned out to be a carbon track on the
rotor - electricity will take the path of least resistance, and the
carbon track was shorting the spark to the conter of the distributor.
Replacing the rotor cured the problem - a visual inspection should give
you an idea if thats it.
Good luck...
Jim Mellander
jmel@netcom.com
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