Classic cars forum & vehicle restoration.

Nic Jarman · Posted: Thu Sep 17, 2009 5:05 pm Post subject:

Can you leave your head lights on for 30 mins. That will tell you if you battery is stuffed. Easy and cheap. My starter had a dead coil that made it start 3 out of 4 times depending apon where the brushes/commutator were. I just turned my dip beams on ( engine not running) and checked the voltage across the battery, it went from 12.24v to 12.08 in about 15 seconds. I have a fairly new battery and I ran it for 15 miles this morning so it is well charged.
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1936 Morris 8 Series 1
1973 MGB roadster
1977 MG Midget 1500
Dax Rush

P3steve · Posted: Thu Sep 17, 2009 11:19 pm Post subject:

before you change the starter first check the engine earth strap they can look ok but be corroded and give a poor conection!

PAUL BEAUMONT · Joined: 27 Nov 2007 Posts: 1281 Location: Barnsley S. Yorks

My bet is a dead cell in the battery, or dodgy battery connections. Sadly from experience it is most likely to be the former. A decent auto electrician should be able to check it for you. Suggest you pick one who does NOT sell batteries!! Laughing

PAUL

Jim.Walker · Joined: 27 Dec 2008 Posts: 1229 Location: Chesterfield

Trying to condense the standard tests for starter and circuit:-

Fully charged battery voltage (off load) should be 13.2 volts. It will be higher when just off charge, so apply a load such as a headlamp bulb for a few seconds to remove the surface charge. For reference 12volts is half charged and 11.8volts is as flat as it should ever be allowed to get to prevent damage.

WITH THE ENGINE CRANKING and the plug leads or coil wire disconnected:-
Battery voltage should not fall below 10.8 volts (if battery is sound)
There should be virtually no voltage drop across any circuit connections.
No more than 0.2volt drop across starter switch.
No more than 0.5volt drop across the starter solenoid (large terminal)connections.
At LEAST 9.5volt drop beween starter motor main terminal and starter casing.
Remember starter body to engine, battery terminal clamps and leads, and the bonding strap between engine and vehicle frame unless the battery earth lead goes directly to the engine are all electrical connections.

Start by testing battery performance and then the starter voltage drop. If these are satisfactory your starter is at fault.
If starter voltage drop is low try the other checks because starter voltage drop will ALWAYS be the observed battery voltage LESS the voltage lost in connections and switches. Ideally the whole voltage loss around the circuit (excluding starter motor) should be less than 1 volt.

Good Luck.
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Quote from my late Dad:- You only need a woman and a car and you have all the problems you
are ever likely to want". Computers had not been invented then!

Finch661 · Posted: Tue Sep 22, 2009 11:41 am Post subject:

thanks so much for the replies, i will have a lot to do this weekend. i have had another look at the connections, and the earthing cable is in a bad condition. my mg never came with a battery clamp, so the rocking motion of the battery seems to of broken several strands of the earth. my plan is to replace the earth cable and positive cable (battery to solenoid), install a battery clamp, remove the starter and associated wiring, clean up the starter, clean up all the connections, then refit! i will see if that makes any difference.
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1985 Mini Mayfare (1275)
1976 Mg Midget 1500

Nic Jarman · Posted: Tue Sep 22, 2009 12:14 pm Post subject:

Yep know that one. I got a cosistent 40mpg to Goodwood and back cruising at around 60mph. Good luck.
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1936 Morris 8 Series 1
1973 MGB roadster
1977 MG Midget 1500
Dax Rush

Penman · Joined: 23 Nov 2007 Posts: 4755 Location: Swindon, Wilts.

Hi
I would check for poor continuity in the starter power cable as well.
I had a Fiesta on which the engine rocked so much that the cable fractured inside the insulation, sometimes it started sometimes it didn't.
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Bristols should always come in pairs.

Any 2 from:-
Straight 6
V8 V10

Finch661 · Posted: Wed Sep 23, 2009 10:19 am Post subject:

just a quick update, i have ordered new earthing straps and a battery clamp set (to stop the battery from moving! i noticed this morning that when i cranked the engine, it was sitting at 6-7V, which im guessing isnt good! when i turn her off then start her again, the volts only fall a little bit. im guessing the battery isnt healthy anymore

i noticed someone said i should look at topping the battery up, how do i check, and what so i top it off with?

i remember when i first bought the car as a project, the alternantor was knacked so the battery was discharged and recharged quite alot, could this be the cause?]

thanks
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1985 Mini Mayfare (1275)
1976 Mg Midget 1500

Jim.Walker · Joined: 27 Dec 2008 Posts: 1229 Location: Chesterfield

Were you checking the battery voltage across the terminals or the clamps? If your connections between battery terminals and the clamps (or whatever kind of connectors your battery has) you WILL get a low and sometimes varying voltage, BUT THAT VOLTAGE IS THE AVAILABLE VOLTAGE. If the voltage across the TERMINALS is OK then CLEAN THE CONNECTIONS!
_________________
Quote from my late Dad:- You only need a woman and a car and you have all the problems you
are ever likely to want". Computers had not been invented then!

Finch661 · Posted: Wed Sep 23, 2009 8:14 pm Post subject:

this was a TIM volt gauge in my cockpit, its linked into the fuse box, so i dont know what that means!
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1985 Mini Mayfare (1275)
1976 Mg Midget 1500

47p2 · Joined: 24 Nov 2007 Posts: 2009 Location: Glasgow

Why not take the car to your local Halfrauds and ask them to check the battery with the load meter, they should do this for free
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ROVER
One of Britain's Fine Cars

Finch661 · Posted: Wed Sep 23, 2009 8:51 pm Post subject:

thats a great idea! i will nip out tomorrow night to halfrauds! luckily i have a trade card, if i need a battery
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1985 Mini Mayfare (1275)
1976 Mg Midget 1500

Jim.Walker · Joined: 27 Dec 2008 Posts: 1229 Location: Chesterfield

You CANNOT rely on battery voltage measured anywhere except directly across the BATTERY POSTS using an accurate voltmeter with a maximum scale of 0-20 volts DC.
_________________
Quote from my late Dad:- You only need a woman and a car and you have all the problems you
are ever likely to want". Computers had not been invented then!

Finch661 · Posted: Fri Sep 25, 2009 10:01 am Post subject:

i have replaced the battery earthing cable and she's now starting a lot better. the starter motor spins a lot faster than it did before. i will check over the next couple of days to see if the problem returns. thanks for your input! Wink

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1985 Mini Mayfare (1275)
1976 Mg Midget 1500

Kelsham · Posted: Fri Sep 25, 2009 3:53 pm Post subject: engine not starting in the cold

When I was young in the 1960s I worked for an electrical car repair dealer. The chief mechanic would test customers batteries by removing the caps and holding a steel bar across the terminals while watching the cells for signs of distress I.E. electolyte bubbling.
He preferred this method to using the correct discharge meter.
I DO NOT ADVISE THIS PROCEDURE.
Gas given off is explosive. I recall the mechanic being a most unpleasant character. The devil looked after his own and the batteries never exploded while I was there.
Of course the discharge meter works in a similiar brutal way but there is no need to remove the caps.
It was lucky the test was conducted out of sight of the customers.