Spitfire experts:
While looking for a long-standing intermittent problem with
my 1979 Spitfire 1500, I studied my Haynes Spitfire manual,
which states that the Spitfire 1500 with the electronic ignition
distributor has a centrifugal advance mechanism and a vacuum
retard (not advance) mechanism. However, when I test the
operation of my system, it seems to be a vacuum advance, not
retard (the distributor plate which now carries the Crane electronic
light source/photodiode, is moved CW by application of vacuum, and
the distributor rotor and light shutter rotate CCW).
The manual was (as I recall) very specific. Is this an error in the
manual? Am I misinterpreting the function of the vacuum advance/retard
mechanism? Did the original electronic ignition somehow function in a
different way, such that the change to the Crane unit could reverse the
role of the movement of the distributor plate to the CW direction?
I did note that the two centrifugal advance mechanism return springs are
different sizes; I plan to order two "correct" springs.
I think I found the problem that has troubled me for a while, the
cable from the Crane photodiode unit was frayed, and the conductor in
the black wire was exposed inside the distributor, and possibly was shorting
to ground intermittently. My symptom was a dramatically changing idle speed,
which seems to have been improved by my repair of this problem. Unless this
black wire is a ground, I think I have found a problem...but I didn't
investigate the function of this black wire, yet.
Regards,
Ray
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Ray W. James, P.E., Ph.D.
Texas Transportation Institute
Civil Engineering Department
Texas A&M University
College Station, TX 77843
Phone (409)845-7436; Fax (409)845-3410
E-mail: r-james@tamu.edu
Date: 12/14/98 Time: 11:42:51 AM
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