ION-related IGN Comments & Coil Quest

[T Hergen]

Shannen,

I apologize for replying so late (I was out of town)...  Regarding the
remote mounted coil in my GM vortec 4.3L V6 S10, it's a '92.  I had a
chance to check the GM manual on the motor, and a coil diagnostics chart
indicates there should be no resistance between any coil terminal and the
frame (I think that answers my question -- please let me know if you think
this is incorrect).  A few measurements with an ohm meter showed it looked
like the common three terminal coils. 

All,

To give people a point of reference for ignition coils, here's a picture
to go along with Bob Hughes post of 5/28 which was seconded by Eric
Schumacher (best explanation I've seen yet, Bob correct me if I'm mangling
your intended description):  (Use a fixed width font to view) 


           ||o-------to plug
primary    ||o
           ||o
Bat+ -----o||o
          o||o
          o||o  secondary
       ---o||o
       |   ||o
       |   ||o
       |   ||o-----
       |          |
       x----------| 
       |
       |
     To Points (or ignition module)

Is this correct for most common inductive style ignitions?  With my ohm
meter, I can't tell what side of the primary the secondary is connected
since I don't have enough resolution on the higher scales.  Various
flavors of CDI may be different, high voltage (primary side) may be
different, and there's likely other systems to which this doesn't apply
(some individual(s) get bent out of shape over anything, so I had I felt
compelled to throw in a long winded "exception" list). 

Some of the posts seem to indicate that the primary and secondary have the
Bat+ terminal in common.  As another poster mentioned, alot of schematics
are artists conceptions.

In any case, in the common ("common" -- there's an opening for anyone who
wants it) three terminal coil induction ignition system, when the points
open (or the ignition module stops driving the coil to gnd) to create the
spark, the return path to ground has to go through the Bat+ terminal
(there isn't any other path to complete the circuit).

Does anyone know which is "right" (maybe both are depending on the
application) 1) secondary has Bat+ in common with primary or 2) secondary
has points side in common with primary? 

Thanks,
Tom
thergen at svn.net


On Fri, 29 May 1998, Shannen Durphey wrote:

> T Hergen wrote:
> > 
> > An autotransformer (the auto has nothing to do with automotive) is one
> > that shares a common connection between the primary and secondary.  Using
> > an ohm meter, you'd find resistance bewteen any two terminals.
> > 
> Thanks.
> > Since you mention the vortec, on mine, I tried measuring the resistance
> > between the high voltage terminal (to the distributor) and the case, but
> > didn't get any reading.  Assuming the coil is okay, this seems to indicate
> > that this coil doesn't use the metal frame as a ground.  Is this what
> > you'd expect?
> > Tom
> No.  Not at all.  But GM has changed a lot of designs
> lately.  What year/vehicle/engine size?
>