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MG MGB Technical - Turning over really slowly

My battery's fully-charged yet the engine turns over really slowly once the car's been left for a few hours. It turns over perfectly once its been started or when its warm.

I'm sure this isn't just a case of a naff battery (only 12 months old & trickle charger meter hardly moves off zero). Any ideas on what might be causing this are welcome.
Paul Hird

There's an earth strap between the engine and body - maybe it's not tightly or cleanly connected ?
Miles Banister

Connect a voltmeter to the hot post (not the connector) of the battery and the hot post of the solenoid and watch the voltage while cranking. Do the same from the ground post of the battery and the body of the starter. Ideally you will get 0.5v or less each time, if it is more than 1v you have one or more bad connections in the heavy current circuit and it is worth going through the battery connectors and the battery and engine/transmission ground straps and cleaning them up. If that isn't the problem measure the voltage at the battery posts and the solenoid while cranking, you should get about 10v. Less than that on the battery and the battery is bad. If that is not the problem then it is probably inside the solenoid or the starter.
Paul Hunt

The problem could be the brushes in the starter motor. They may be worn out. I had a similiar problem, though not with an MG, It was a chevy 350 starter.
corey

Thanks to everyone for these helpfull suggestions - I'll be working my way thru the system this weekend.
Paul Hird

This thread was discussed between 18/03/2002 and 19/03/2002

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