[DeTomaso] MSD failure update....

Doug Braun doug at silicondesigns.com
Thu Apr 19 16:15:52 EDT 2007


Mike,

	One item I'd recommend you add to your MSD setup is a transient voltage
suppressor diode across the main power and ground leads close to the MSD6.
The one I used is under the general part number of 1.5KE20A.  You install it
with the lead adjacent to the band on the diode's body connected to 12V.
This little gem will absorb up to 1500 Watts peak of transient spikes on
your 12V power to protect the MSD.  Such spikes occur every time you turn
off a fan or start the car.  It won't start clamping until the voltage gets
up above 17V so if your voltage regulator is running high it won't cause a
problem.  But it'll really clamp hard at 20V and above to protect the MSD.
They're available from Digi-Key
http://www.digikey.com/scripts/DkSearch/dksus.dll?Detail?Ref=165974&Row=1447
7&Site=US

Doug Braun
blue 73L #5505

-----Original Message-----
From: detomaso-bounces at realbig.com
[mailto:detomaso-bounces at realbig.com]On Behalf Of MikeLDrew at aol.com
Sent: Monday, April 16, 2007 10:17 PM
To: detomaso at realbig.com
Subject: [DeTomaso] MSD failure update....


Hi guys,

An update on my situation from yesterday:

Jim Seiferling, who has plenty of electrical/ignition smarts, came over this
afternoon and re-troubleshot the system; all clues pointed to a bad MSD box.
It was solidly bolted to the firewall, as far from the motor as possible
(but
still rather close).

Zipped out to Kragen's and bought a new box; with my military discount it
was
only about $20 more than it would have been from Summit--a small price to
pay
for right-now service.

The rubber isolators are intended to be slipped through a piece of
sheetmetal
(firewall etc) and secured on the back side with nuts, and then bolts thread
into the outside of them to secure the MSD box.  I have a double-firewall on
my car, so the inside isn't accessible.  This would have been a perfect
application for Rivnuts, but I didn't have any lying about, so instead I
hacked the
stud-end off the bushings and drilled them out, then we mounted the box
using
#8
sheetmetal screws (which is how the old box was mounted, minus the
bushings).

It is now isolated both from vibration, and from radiant heat.  The
stainless
steel firewall absorbs as well as reflects heat, and that heat would
undoubtedly be transmitted to the MSD box; having it stand off by a half
inch or so
can only do it good.

The car fired right up once all the wires were hooked up--hooray!

We then tackled anomolies with my front turn signals and marker lights.  We
finally managed to get both of them working properly.  The driver's side was
malfunctioning because there was no bulb installed (DOH!!!!) and the
passenger's
side was dorked up because the wires from the harness to the light had been
hooked up incorrectly; the turn signal element was lit with the running
light
circuit, and the running light element with the turn signal circuit.

We discovered these things only after we had chased wires, opened up
electrical connectors, shot everything in sight with WD40, etc. etc.  We
wound up
wasting a couple of hours looking for complicated causes for what turned out
to be
very simple problems, but at least I *know* the system is good now.

That's today, however, and this *is* a 35-year-old Italian car, after
all...so no promises about tomorrow!





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