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MG Midget and Sprite Technical - Battery won't spin up my 1380

Battery is 2 years old, from Halfords. Even in this warm weather on attempting to start it manages a few revs then the battery runs out of juice.

When I add a jumper battery pack it start immediately. The engine has high compression and quite a lot of advance. Is the strater struggling against the compression and early ignition or is it simply the battery? How does one measure a battery?

Thanks, James
James Eastwood

take the battry in to a battery shop and have them test it, sears, autozone, advance auto parts ect its most a free test and takes about 5-20 can show 12 volts and still be a dead battery. your looking to see if it can hold a charge

also have a look for corrosion (white powder) (and green scale) on both in the cable wire strands and on the cable attachments...many times it will look okay untill you atually pull the cables off to reveal the mess


The easiest test you can do at home is --- Turn on the headlights and try the starter. If the lights go dim you have one of three problems. #1 -bad battery #2 poor battery conections both ground and positive sides including the grounding strap frame to engine #3 bad starter.
This should cover 99 % of your problems.

Sandy, Prop thank you.
James Eastwood

It is probably either the starter or the battery.

To find out, first charge the battery.
Then with an ammeter on the pos batt cable turn the engine over to see how much the starter is drawing. Check the number to see if it is in spec.
If it is then recharge the battery. Check the voltage and make sure it is fully charged. Then with the voltmeter connected to the battery turn the engine over checking to make sure the voltage does not drop to 10v or less while the starter is turning the engine over.

I forgot to add that after the voltage drops while the starter is turning that it should jump back to the full charge value or very close to it.

It's possible that your alternator is overcharging the battery and 'boiling' the electrolyte away, i once had this with a ford escort, changed the alternator and i didn't have to top the battery up after that and the starting problems went away...

I also had a starting problem with a Vauxhall Carlton 2L GLi, it would start in the morning when cold but once the engine was warm it struggled to turn over, this turned out to be the field windings in the starter, the insulation was melting whilst hot and causing a short but it was OK when cold..
I fitted another starter and it spun over twice as fast as it ever had up to that point..

An amusing thing hsappened with that car when i parked in a lay by to get a sandwich and cup of tea from one of those vans, i parked facing uphill on the uphill side of the van not thinking about the starter problem..
I ate my sarni, drank the tea then the car wouldn't start so i tried pushing the heavy bu**er up the hill to bump start it in reverse but i only managed to get it about thirty feet so a chap that was stood in the queue helped to push me..
when i was far enough away from the van, i stuck on the handbrake, i then jumped in the car, switched on the ignition, selected reverse then let the handbrake off and started rolling back, the chap decided to help me back by pushing the car from the front end...
As soon as i let the clutch up the car almost stopped due to the veruy low reverse gear, the bloke couldn't stop and slid right up the windscreen!!!..

I apologised profusely but the bloke just couldn't stop laughing, i daren't just in case!!

j b biggs

~12.7v with engine off

~14.4v with engine running

this will at least let you know if the alternator/dynamo is working

Have your voltage regulator set (in the case of a dynamo) by an experienced auto spark

If you happen to be on an alternator, sometimes you find the connectors dont sit nicely in them and as such you find he charge is weak, and may even throw on your ignition light whilst driving.


This thread was discussed between 23/06/2010 and 05/07/2010

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