TR7 & TR8 Mailing List

RE: Electronic ignitions

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"Jim Altman"

RE: Electronic ignitions
« on: September 22, 2017, 10:22:19 AM »
Good catch!  I looked in the cap and not only is the center button the right
color grey for the dust, but itbs very loose.  Thankfully, I replace the cap
on a schedule rather than as needed, never throw anything away, hence have an
old one sitting here that was just fine when removed from service.

Thanks, lets add this one to the hints database.

Jim Altman

From: Brian Lanoway []
Sent: Friday, September 22, 2017 9:10 AM
Subject: RE: Electronic ignitions


I had a similar ignition failure with the Crane system on my TR8.   I also had
significant dust inside my distributor.  In my case, the carbon button inside
the dome of my distributor cap had failed.  The button ultimately broke off,
bounced around inside the distributor and damaged the Crane optical trigger
and the advance springs.  I would assume that given the amount of dust packed
inside my distributor, the failure process was underway for some time before
the button broke off and my engine stopped.

Your dust may have come from elsewhere, but just to be safe, check the carbon
button in your distributor cap.  Better yet, even though they are new, replace
both your distributor cap and rotor again.  I had heard somewhere that there
was a faulty production run of blue caps. FWIW, my failed cap was blue.

Brian Lanoway

1980 TR8

Date: Thu, 21 Sep 2017 14:41:02 -0400
From: "Jim Altman" >
Subject: RE:  Electronic ignitions

Well, here is the next chapter.  I went into the dizzy to look to see if new
XR700 units use the same optical pickup as old ones.  (Could I just replace
the control unit?)  Inside the dizzy was an UNBELIEVABLE quantity of packed
dust.  I took things apart and I have no idea where the dust had come from.
There is no indication that anything was rubbing on anything.  The trigger
wheel is not grooved or cut into, the sensor was nice and evenly spaced above
and below the wheel.  I had put a new rotor and cap on last spring and both
appeared fine.   Nor was there any dust in there last spring. But, the gaps
the trigger wheel were seriously impacted with dust.  I cleaned it all out
been driving around and it now seems fine.  The engine clearly is running
better and cooler.

So, electronic gurus (Jim T?), could obstruction of the light beam,
from making the car run like crap, cause overheating of the control unit?
It's easy to anthropomorphize the control unit and say it had to "work
with weaker signal from the sensor, but it either gets a sufficient signal
triggers a spark or doesn't.   The "kinda" signal ought to be enough to
trigger the unit or not.  But, then I have not seen a schematic of the
units innards to really know what's going on in there.

So, I have a replacement unit (Thanks Ted) which for the time being is going
to sit on the shelf while I see what happens next.


Sent from my Apple device.