[TR] Testing ignition coil: what am I doing wrong????

[Randall]

> I did get some 
> sparks from the 
> ground wire when I broke the ground

Try adding a condenser to the circuit.  Also make sure there is nothing on
the secondary side that could bleed high voltage to ground (like a glazed
spark plug).  The problem may be the way you are breaking the primary
circuit (those sparks are drawing energy out of the coil), but I'd try the
condenser first.

Delco HEI used different kinds of pickups.  If it just has two terminals,
then it is a simple inductor coil.  According to my GM book, the coil DC
resistance should be between 500 and 1500 ohms; and infinite from either
lead to ground.  If it has 3 terminals, it may be a Hall effect transistor.
There is a test procedure given, but it requires applying 12v and a magnetic
field to the pickup.

I also thought coil failures were relatively rare, but I've had 3 of them on
my TR3 in the past 3 years; and the HEI coil on my GM car has been replaced
several times as well.

-- Randall