Re: Ignition Redundancy

["Bill Thebert" <bthebert@domain.elided>]

John Landry:

I'm not sure what kind of instructions your "emergency card" contains for
bypassing the MSD unit, but here's a little story from the Tuesday trail
trip at RMIHR:

My Mallory Hyfire ignition module is wired to the coil with 4 wires.  I
don't have the precise schematic handy, but two little plastic insulating
spacers (shaped rather like a single link on a bicycle chain) go onto the
coil terminals.  Still only two contacts to the coil per se, but 4
"terminals" in all going to the Hyfire.  

There's a "flat four" trailer-style connector just before the Hyfire. 
Mallory ships a little "loopback plug" that is compatible with the Hyfire
side of this flat-four connector.  Separate the connector and apply this
loopback gadget, and the Hyfire is effectively out of the system in under
15 seconds.

On the way to the trailhead on Tuesday, I hit a bump and instantly lost all
ignition.  Turns out that a power supply wire to the Hyfire had abraded
where it passed by the alternator bracket (poor routing on my part).  It
shorted to ground and arced thru the entire wire -- effectively severing
it.  Once I located the problem, it was a 10-second fix to apply the
loopback connector from the glovebox.

I relate this story thinking that you might be able to design a circuit to
just as "handily" re-wire your ignition without actually "re-wiring" it.

Regards,

Bill Thebert