Stag and elect. ign. questions

[Mike Wattam <MikeWattam@domain.elided>]

Hi Henry

Hmm, I hate electrics.

Lumenition is not that good, it can be real unreliable at times.  It's
worst foible is usually overheating, when it just stops working until it
has cooled down again. 

However, it may be there is an easy answer here.   First, if you have the
capability of refitting mechanical points to your distributor, rip out the
Lumenition and see what happens.

On the Stag, the ignition system works in normal mode at 6 volts.  For
start-up there is a resistor fed off the starter which switches the supply
to (nominally) 12 volts so that the spark plugs get a really meaty spark to
fire up.

On the MKI there is a small ballast resistor beside the coil and wired into
it, which regulates the supply to 6 volts running.  As your car is a MKI
then look for the ballast resistor to confirm.  

On the MKII this external ballast resistor was changed to a resistor wire
running inside the wiring loom.  Could it be your car has the later wiring
harness with the resistor wire AND got the external ballast resistor as
well?  If it has the external ballast resistor, substitute a plain wire
from the ignition switch back to the ballast resistor and see if it now
works well.  Alternatively, the Ballast Resistor may have developed a very
high resistance which is causing the wirng loom back to the starter, to
overheat.

My guess is the resistor wire inside the wiring harness has overheated (or
a faulty external ballast resistor) and caused your wiring problems.  The
resistance should be 1.3 to 1.4 Ohms.

Also note the connection on the starter solenoid is often the cause of
problems, it is a very small spade connector which loosens/wears with
engine movement, creating a bad connection.

Please get back to me if the above does not trace the problem.

Mike Wattam
Chairman - Triumph Stag Register