At 08:01 PM 8/8/04 -0400, Mike Razor wrote:
>MGA won't start. Pull on the starter knob and get nothing, just a little
>click.
A little click? How little? Was it barely audible, like only the contacts
of the manual switch? Or did it make a louder click like something may
have moved when the switch made contact?
>.... the battery .... was in good shape. .... removed the starter. .... In
>the past I could put a set of jumper cables on the starter and if working
>it would spin. When I do that to this starter all I get is a bunch of
>sparks. ....
A common starter failure is a breakdown of the insulator parts where the
input power post goes through the end plate. This results in a short to
ground at the input connector. It is repairable. Remove the end plate and
replace the phenolic or nylon insulator parts around the input post. These
parts would originally be a phenolic shoulder washer and a phenolic flat
washer. More modern replacement parts might be molded nylon. If you don't
have a shoulder washer insulator, you can replace these parts with two
phenolic flat washers and a tubular insulator.
When assembled the power stud passes through the end plate and must be
electrically isolated from the end plate. At the same time it must have
good electrical contact to the heavy wires inside and outside. With the
end plate in place, tighten the first hex nut securely enough to achieve
good mechanical and electrical contact for the wire inside (if that wire
was not welded to the threaded stud). If using nylon washers for
isolators, do not overtighten the nut, as this could completery smash the
nylon parts and cause another short to ground.
Also use due dilligence not to break the power input stud or to strip the
threads on the stud or in the nut, or lose that "funny" brass nut. These
are (originally) brass parts having "not so strong" threads. The threads
are also an odd pitch by modern standards, which makes these parts "Jesus
bits", not obtainable at your local hardware store.
You can measure the resistance with an ohm meter from the input stud to the
end plate, but don't expect much (litterally). The resistance will be very
low, because the starter motor is capable of drawing a couple hundred amps
under load. Depending on the sensitivity and accuracy of your ohm meter
near zero, and the quality of internal connections and brushes inside the
starter motor, you may see resistance of perhaps 3/10 ohm and maybe less
than 1/10 ohm (100 milli-ohm), BUT NOT ZERO.
As you said, when you hit it with jumper cables it should turn
smartly. Big spark and no motion indicates an internal short.
Barney Gaylord
1958 MGA with an attitude
http://MGAguru.com
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