Barney,
> What that leaves is a starter motor that is connected well enough
> electrically to draw 200 amps but doesn't put out much torque. Sounds like
> a bad starter to me. Put a voltmeter directly on the input terminal of the
> starter motor, with the second meter lead grounded on the housing of the
> starter motor. If it reads at least 8 volts when it's cranking slowly, it
> probably has some internal short. If it reads closer to 12 volts when
> cranking slowly, then probably some internal open circuit(s) in the
> armature, or maybe a bad connection for the brushes on the armature.
Ohms law, ohms law! High current flow cannot be caused by both a short and/or
open circuit. High current flow in the starter can be caused by high
mechanical resistance or low electrical resistance. When resistance goes down
current flow goes up. When resistance goes up current flow goes down.
One other possibility is that the battery is not well and the "200 amp"
booster isn't.
Rick Ewald
In a message dated 3/19/99 9:40:12 AM Pacific Standard Time,
barneymg@ntsource.com writes:
> At 09:07 AM 3/19/99 -0600, Perry Robinson wrote:
> >.... I have a 1961 MGA 1600 .... the engine has maybe 6,000 miles on it
> since a full rebuild. .... never had a problem.
> >
> >.... When I go to start it, it turns over very slowly, .... as though the
> starter is straining to turn it. Sometimes the jumper cables get very hot,
> or the circuit breaker trips on my 200 amp booster. I have repalced the
> starter twice, with a "guaranteed" starter, but no luck.
> >
> >.... you can push it to a good roll, pop the clutch in second, and it will
> buck once, this start like a champ!? I've been told that I may have a piec
> of crap starter, that the ground strap may not be good (checked that), or
> that my static timing may be too far advanced. ANY IDEAS?
> >....
>
> The timing could be too far advanced, such that it fires before TDC and
> causes a kick back that stops the starter from getting it over the top.
> However, If it started okay before it was parked, it's not likely that the
> timing could have changed that much by itself, so probably not.
>
> 200 amps is about the right current if the engine was very stiff and the
> starter was working very hard to turn it. However, as you can easily push
> start it, the engine is turning freely, so not that much load for the
> starter. An engine of this size should crank over with about 100 amps.
>
> What that leaves is a starter motor that is connected well enough
> electrically to draw 200 amps but doesn't put out much torque. Sounds like
> a bad starter to me. Put a voltmeter directly on the input terminal of the
> starter motor, with the second meter lead grounded on the housing of the
> starter motor. If it reads at least 8 volts when it's cranking slowly, it
> probably has some internal short. If it reads closer to 12 volts when
> cranking slowly, then probably some internal open circuit(s) in the
> armature, or maybe a bad connection for the brushes on the armature.
>
> Barney Gaylord
> 1958 MGA with an attitude
>
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