Re: ihc-digest V5 #203

[jlandry@domain.elided (John A. Landry)]

An example of <hofs@domain.elided>'s troubled thought patterns:

>>From: ScoutFreak@domain.elided
>>Subject: how to connect msd to scout distributer
>>
>>i connected an msd ignition system to my existing distributor. i have a 1976
>>scout II with electronic ignition. it doesnt work! i followed the mfg. wiring
>>dia. concerning the magnetic pickup distributor. i did not use the gold box,
>>is this where i went wrong, because the schematic doesnt show the gold box.
>>can someone please lend a helping hand in being very explicit in how to
>>connect this system correctly.

>You don't need the gold box. If 
>calling MSD doesn't, for some reason appeal to you, say so and I'll go 
>dig up my schematic and see if I can help. Memory won't help in this 
>case, because I replaced a Prestolite system including the distributor. 

Unfortunately, you *absolutely* need the Holley "gold box" when you install an
MSD system on a Scout II so equipped with one!

The MSD system can be triggered in two different ways... by the
"make-or-break" signal which comes from the wire connected to the negative
coil terminal on just about any ignition system.  The other method is by a
wave form signal output from a magnetic pickup.  The pickup you see inside
your Holley electronic distributor is *not* a magnetic pickup and thusly will
not directly trigger the MSD ignition system.  It works under a completely
different principle.

In the case of the Holley, a very low amperage alternating current is applied
to a coil inside the pickup.  This sets up an electrical field.  As the
reluctor (star wheel) teeth pass the pickup, the field is disturbed.  It's
much like the same way a metal detector works.  This disruption is sensed by
the gold box and is converted to a make-or-break signal for the coil.

The Prestolite electronic distributor works the same way, except that
everything is internal to the distributor.  The pickup you see inside the
Prestolite distributor works the exact same way the Holley does.

In the case of a true magnetic pickup, no current is applied to the coil.
Instead, a the wire coil you see surrounds a magnetized piece of metal in the
center.  As the reluctor teeth pass the magnetized piece of metal, a "pulse"
of current is generated in the wire coil surrounding it.  It's a mini
generator so to speak.  The MSD system is capable of turning these tiny pulses
or "waves" of electricity into the make-or-break signal the coil needs to
operate.

So, to connect the MSD system to your Holley gold box (for sure in the case of
the MSD 6A) you connect the white "trigger" wire from the MSD to the brown and
then black wire (marked 16E) coming from the gold box.  This is the wire which
was originally hooked to the negative terminal of your coil.  Other than that,
you connect all of the other MSD wires as directed in their instructions.  The
two original wires marked 16 and 16D originally connected to the positive
terminal of the coil need to be removed and connected together.  Keeping them
together supplies power to your gold box.  This same connection also makes a
good place to connect the thin red wire for the MSD control unit.  When the
ignition is on, you'll then power your gold box as normal and also turn on the
MSD control box.

Here are simple connections to make it work in your truck...


MSD 6A Wires                 76 Scout II


Green Mag Pickup             Not used

Violet mag Pickup            Not used

Heavy Red                    Positive (+) Battery Terminal

Heavy Black                  Chassis Ground or Negative (-)
                             Battery Terminal

Black                        Negative (-) Coil Terminal
                             (No other wires connected here.)

Orange                       Positive (+) Coil Terminal
                             (No other wires connected here.)

Thin Red                     Junction of wires 16 and 16D
                             originally connected to negative
                             (-) coil terminal.

White                        Wire 16E originally connected
                             to positive (+) coil terminal.

That's it!  Leave all of the other wires connected and she'll work fine...
unless you've damaged the pickup in your distributor (not likely).  Try it as
directed above first.

If you'd like to convert your Holley distributor to a magnetic pickup, it can
be done without much fuss and I'll provide detailed instructions at some point
in the future.

Regards,

John
------------------------------------------------------------------------
jlandry@domain.elided             |
Conservative Libertarian        |  Scout(R) the America others pass by
Life Member of the NRA          | in the Scout Traveler escape-machine.
WA Arms Collectors              |
Commercial Helicopter - Inst.   | 1976 Scout II Traveler "Patriot" model 
http://www.halcyon.com/jlandry/ |     1977 Scout II Traveler (Parts)