A weak spark can be caused by a bad capacitor. A bit difficult to do an
absolute check without a capacitance meter, but if you connect a spare plug
to the king lead from the coil and lay it on the block, turn on the ignition
and flick the points you should get a good fat spark at the plug. However
if you interrupt the lead between the coil and the points you will only get
a weak spark at the plug. The difference is the the effect the capacitor
has. In your case, if you get the same spark with both methods then your
capacitor has had it. Unfortunately, if your capacitor is only half bad you
will see a difference in the above tests, albeit not the full difference,
which you will only see with a known good capacitor.
PaulH.
-----Original Message-----
From: Edwin Vaughan <vaughme@mail.auburn.edu>
To: 'MG NUTS' <mgs@autox.team.net>
Date: 19 February 1999 21:36
Subject: MGB weak spark or the little engine that could...not start!
>
>Hello All,
>
>My '77B will not start. It turns over, has good compression, the fuel pump
>is pumpin', the carb is receiving the fuel, and my coil is receiving
>the 12 V from the battery, though I don't know if it is stepping it
>up or not. It wants to start, its trying. However, while checking the
>spark I noticed it was quite week. My trusty Haynes manual stated that a
>wet distributor could cause this. My heater-water valve does leak. Has
>anyone else had trouble starting their MG and find a leaky
>heater-water valve, which had soaked the distributor, to be the culprit?
>
>TIA
>
>Edwin
>
>"I try to think but nuthin' happens" http://www.auburn.edu/~vaughme
> -- Curly (the stooge)
>
>
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