[Mg-t] Questionable Starter

[Stuart C. Keen, Jr.]

How do I test the starter in a TD? The starter turns the engine, but in slow
motion - i.e. Lugging effect.

1) I have replaced the Optima battery with a new Interstate one with 700 amp
cranking power.
 
2) I have cleaned all electrical contacts between the battery and the
starter. 

3) Since ground is often the culprit in a Lucas system, I ran a jumper cable
between the battery ground and the starter, but this did not help.

4) I checked the starter brushes and their respective wires and all was
okay. 

The only two items left untested are a) the starter switch and 2) the
starter itself. 

The evidence is: When I try to start the TD, it lugs (thus my initial
suspicion of battery or wiring problem). It appears to be zapping the
battery (like overload) because if the XPAG engine does not start by the
third attempt, there is not enough amperage to crank one more time.

Then I tried to make a compression check. Each crank only built up the
compression to 30 psi (in the old days it would virtually jump to 150).
That's what I mean by slow motion. The highest it would climb was 90 psi (3
cranks) and then the battery was too zapped to turn the engine anymore.

I tried to minutely adjust the mount of the starter so not a tight meshing
of gears between the starter pinion and flywheel (ring gear), but nothing I
did helped. 

I am suspecting a shorted field wiring or something like that in the
starter, but do not know how to test in house.

Thanks for any insight and suggestions.

Stu Keen
1951 MGTD Mark II

PS You might say I am now paying the price for insanely driving this 58 year
old MG from Venice, Florida to Prince Edward island, Canada (5,604 miles
round trip - 26.03 mpg, 8 qts of oil), arriving home a week ago. The starter
problem began on the return trip, outside Albany, NY. Parking on hills and
pushing were the methods of choice to start the TD. Kept ye old hand-crank
in reserve.