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MG MGB Technical - slow starting when cold?

i have a 1968 mgb rd and when i go to start it in the morning the starter goes normal speed for about half a sec then slows down.....i dont think this could be caused from a dead battery because i have a battery disconnector switch and after it starts the first time it is fine...i have left the battery connected during the day for 12 hours and it still works fine but after 10 hours at night it goes bad...what is the reason for this? any help or info would be great


thanks everyone

scot
Scot Hamm

It could be a corroded connection somewhere in the high-current connection from the battery to the starter. Check the battery connections.

It could also be that your battery is beginning to fail. I once had a battery go bad in such a way that the internal resistance of the battery went very high. When drawing heavy current, the increased resistance caused the voltage to drop drastically. However, the dash lights, radio and other low-draw items worked fine.
Paul Noble

Scot,

When your starter slows down, does it happen suddenly - as in first we're turning at 300 RPM, then suddenly we're turning at 100 RPM. Or does it wither down - starting at one speed, then gradually to a slower speed?

Matt Kulka

I agree with Paul. Put a voltmeter on the battery posts (not the connectors) while cranking, disconnect the coil to make sure you can crank and not start. If the voltage drops much below 10v when it goes slow it is the battery. If the voltage *rises* slightly when the starter goes slow it is connections. You can check the connections by putting the voltmeter on the hot post of the battery and the hot post of the solenoid, and again on the ground post of the battery and the starter body or any decent engine ground. Ideally you will only get about 0.25v each time. Anything more than 1v is definitely worth investigating, I have seen cars losing 3v in the heavy current circuit. Putting the voltmeter either side of the various connections in the circuit like post to connector, connector to cable, connector to ground etc. allows you to localise any bad connection. An analogue voltmeter is usually best.
Paul Hunt

Try starting with the clutch out, car in neutral. If it starts normally, you may need to reshim your crank.
R. L Carleen

there is no slowing down process. it goes as Matt said from 300 to 100. i always start it with the clutch out and in neutral

thanks
scot

This thread was discussed on 08/05/2003

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