I've just had a very similar problem on my V8 with hot starting, sounded
like a flat battery even if tried immediately after switching off. That
turned out to be plugs - self-inflicted, I realised I hadn't changed them in
25k miles.
Ordinarily the first thing to do would be to measure the voltage while
cranking right on the battery posts, if you see 10v or better it's not the
battery. Does an MGA have twin 6v batteries? If so do each battery
separately (5v or better is good) as the problem could be in the link cable.
Otherwise it could be in the connections anywhere from there to the motor,
or in the motor itself. So the next step is to measure the voltage on the
motor terminals while cranking, and compare that with the battery voltage.
Ideally the motor will only be about 0.5v lower, if it's more than one volt
(and I have seen more than 3v lost) then it's worth breaking the heavy
current circuit down into sections for measurement.
PaulH.
----- Original Message -----
> The starter on my 1960 MGA works fine when I first start the car, however,
> after driving several miles it barely turns. It acts like a car with a
> low
> battery, but I know my battery is good.
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