Folks:
I've just finished doing a bunch of rewiring on my TR6, which had an
ignition switch failure on December 30. I've replaced the ignition
switch and fixed a bunch of 'hacks' on the wiring under the dash.
I've got two problems which remain. At the time of the failure, I
had two problems which seemed to happen simultaneously:
First, the spark went away. That is, no voltage at the positive side
of the coil with the key in the 'on' position. Replacing the
ignition switch has solved that specific problem, as I do now have
voltage at the positive side of the coil with the key in the 'on'
position.
Second, the purple circuit fuse blew. Further testing with the help
of Dan Masters via e-mail AND via his excellent electrical manual
indicates that somewhere in the purple circuit there is a short to
ground. This problem I think I can find myself, but I'm including it
here just for background.
However, even though I now have voltage at the coil, the engine does
not want to start. This car historically has always started very
quickly, even after sitting dormant for several weeks at a time, even
in the cold garage. I have confirmed that there is no spark. I
started to suspect that perhaps the ignition module was damaged
somehow when the failure took place. So, in an effort to avoid
temporarily installing the OEM breaker points as a means of
diagnosis, I decided I could take advantage of the fact that I just
recently installed a Crane XR700 ignition system on our Toyota. The
two systems, as I understand it, are functionally identical, although
Crane has added an LED indicator which is pretty handy. So I turned
the Toyota over to line up the timing marks and verified that the LED
was lit. (key 'On') I then disconnected the plug that connects the
three small wires which go to the optical pickup in the dizzy, and
measured the voltage at those three wires. Here are the results:
Grey: 1 volt
White: 0 volt
Black: 4 volts
Now: What I expected was that if I align the timing marks on the TR6
in the same way (although there's no LED indicator) and then measure
the voltage at those same wires, then either I would get the same
numbers as on the Toyota or I would get no volts at all, which may
indicate that the module is toast. Make sense?
Well, of course it didn't turn out to be quite that simple. First of
all, the three wires on the Crane system at coded Grey, White and
Black. But the same wires on the Allison unit are coded Clear, White
and Black. It appears that the clear wire corresponds functionally
to the grey wire on the Crane unit. So, the results from that test
are as follows:
Clear: a little less than 2 volts
White: a little less than 1 volt
Black: 6 volts
I would assume that since I have voltage at these wires means the
module is okay. However, my assumptions, particularly in the context
of electrical stuff, have been wrong before.
So now I've shown, in theory, that the module is okay. I even
adjusted the optical pickup, following the Allison instructions for
positioning the pickup properly, which involves pulling the coil
wire, setting it next to a ground and sliding the pickup around until
you get a spark. And I got a spark from the coil wire. But guess
what? The car still won't start.
I pulled the coil wire again, set it near a ground and cranked the
motor. The coil wire sparked just fine with every revolution. I
pulled a plug wire off, stuck a spare plug in the end of it could NOT
get a spark. Then I grabbed my timing light and put the inductor
around the #1 plug wire, pulled the trigger on the gun and cranked
the engine. No flashes. No spark. Then I put the inductor around
the coil wire, pulled the trigger and cranked the engine and still no
flashes and still no spark.
So that all makes me think there IS something wrong with the ignition
module. Next step, I suppose, is to reinstall the points and try it
that way.
Can anyone make any sense out of this?
I assume that Crane will honor Allison's lifetime warranty on this
XR700 system.
--
Pete Chadwell
1973 TR6
/// triumphs@autox.team.net mailing list
/// To unsubscribe send a plain text message to majordomo@autox.team.net
/// with nothing in it but
///
/// unsubscribe triumphs
///
/// or try http://www.team.net/cgi-bin/majorcool
|