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MG MGA - Batteries

I always have some trouble starting my MGA initially and often run the battery flat. Degree of choke doesnt seem to make much difference.I am using a 12 volt battery in 1 of the bins. I am wondering whether I can put another 12 volt battery in the other bin and connect the two in parallel to give more capacity. will this work and are there any drawbacks? For instance will the dynamo be able to charge both batteries? Would the cutout work correctly?
Hugh Davy

Sounds to me like your timing, mimxture and plug settings could all do with a once over. The car should not be hard to start.

It's also worth chaning the condensor and points, as condensors can deteriorate and lead to this starting problem.

dominic clancy

Hugh

Yes you can. I have the set up in my car, purely because I had a spare battery and thought it would be more useful in the car than on the garage floor. However, I have an isolator on each battery and only normally have one 'live' at a time. The only time I ever have both on is momentarily on the very rare occasion, when like you, I find the single battery struggling. As soon as the engine fires I isolate one of the batteries. Each day I alternate the battery in use.

I have had this arrangement for the last 6 years I guess and have not had to replace either battery as yet.

That all said, it is probably worth checking over and cleaning all your connections between the battery and starter motor. Better to cure the cause than treat the symptons. It is on my list of things to do this winter.

Steve
Steve Gyles

Thanks guys. Dominic I changed the distributor to an electronic 123 which has no points or condensor but although the car goes very well the starting problems remained. I will have the local experts check the carb settings.
Hugh Davy

I'm with Dominic. 2 x 12V in parallel is overkill and you should correct the true cause of poor starting.
Art

Hugh,
These cars should start easily. I had a 62 Sprite which started well at -20F. I start my MGA without a problem if there is a January thaw. And in the spring it takes about 30 seconds for the first start of the season.
I have my doubts about the battery, unless it is defective. A lead acid battery doesn't last forever. With or without use. It should turn the engine for quite some time. If it dies quickly, it is defective or you have a poor ground. (battery to frame or frame to engine).
Mike

Questions.

We (myself included) always harp on about cleaning the battery terminals, earth connections, etc. Rarely do we mention the starter switch. Obviously, the terminal posts can be cleaned, but what about the internal contacts? Do these erode badly and build up high resistance? Could the switch be the prime cause of Hugh's problem?

I am not an electrician, so I am looking for advice. Is there a way of checking the resistance across the terminals? If so, what should I be looking for on a meter?

Steve
Steve Gyles

The starter switch cannot be disassembled, but is generally not a problem. Inside it has a large copper plate that bears against a pair of copper bolt heads for contact, very good very high current and very durable. Most original starter switches still work fine 50 years on, including mine with 355,000 miles on the car.

To check starter cable connections you need either a low range ohm meter or a volt meter. Working with only 10 volts or so for cold start cranking, you can't afford to lose much. You have to be able to pull about 200 amps through the starter circuit wi 10 volts, so the entire circuit cannot have more than 0.05 ohms (50 milliohm) resistence. If you have 1/4 ohm (250 milliohm) resistance across any one cable connection you're screwed.

It is difficult to measure resistance that low, as the probe contacts may have higher resistance. The more reliable way it to use a volt meter across a connection and measure voltage while cranking. Resistance of 50 milliohm may show 6 volts across the connector when attempting to draw a high current.
Barney Gaylord

The starter switch can be disasembled. I have done it and been successful at cleaning up the contacts. Reassembly requires recrimping the housing. Fun to do for the education but not really worth the effort. At the present price of a new switch, I would recommend buying a new one if you find the original one to be faulty.

There will always be some voltage drop along the cable from the battery during cranking. This voltage is dependent on the resistance of the wiring, contact resistance of all the wire crimps, the starter switch resistance and the current drawn by the starter.

Most electronic devices are designed for a minimum operating voltage. If the voltage drops below this the device may not work. This may be the case with the electronic ignition. Did you change to the electronic ignition in attempts to fix your starting problem? If not, I'd try to install an original disty and see what happens.

Does the starter crank at a normal rate of speed? If so, you can pretty much dispell most of the above comments. If not, then fix that problem. A second battery in parallel will help with the voltage drop at the battery since each battery will supply only 1/2 the current. But it will not fix the voltage drop along the cable and interconnects.

An original wiring system wants to have ~.025" plug setting. Too high a gap will cause arc over at other places preventing starting. Also, a mis-adjusted choke setup can easily cause excess cranking at cold start.

Chuck
Chuck Schaefer

Hugh,
I used to have trouble starting my A. I found pulling the choke knob out even 1" wasn't pulling the main jets down - combination of linkage wear and cable adjustment - fixed that and problem solved. Easy way to check this is to start the car from the engine compartment. One hand reaches down and pulls the mixture linkages up to richen mixture - other hand reaches across engine and pulls the starter switch. If engine starts you need to look at your cable and linkages.
Regards
Mike
Mike Ellsmore

We have 2 themes running here. I think we need Hugh to clarify if it is slow cranking speed, or the engine simply not firing.

Steve
Steve Gyles

I had the problem before I changed the dizzie which had no effect on it. The engine will spin but not fire soon enough and the battery runs down. Juggling with the choke control and/or accelerator doesnt help. I started it this morning using a booster pack but the thing that really got it going was squirting easy start into the air intakes. Maybe it is actually the choke setting.
H L Davy

When I had SUs mounted, fopr cold starting, I had to pull the choke RIGHT out (so the inner shaft of the knob came out of the fixing) to get a quick start, then I could push it back in.

With the Holley, I always have to prime with one pump on the pedal (the accelrator pump then squirts a charge into the inlet manifold)

You may simple need more choke than you are giving.
dominic clancy

I would put my money on choke linkage wear and misadjustment. The MGA linkage is a bit like the rigging on a biplane. There are a lot of wear points and the accumulated wear can really make things very sloppy.

Good luck!
Rich
Rich McKIe

Hugh,
I would check with a small mirror that when you pull the choke knob right out that you actually lower the carburetter main jets. Let us know the gap between the jet head (clevis) on the end of the jet and the adjusting nut when you do this (see page D.12 of the MGA workshop manual) - before you pull the choke out there should be no gap.
Regards
Mike
Mike Ellsmore

Hugh

If you try jump starting your "A" from another 12v battery/car, by connecting that supply to the live side of the starter switch, (be careful & check polarity!) you can readily check the starter, the switch, engine earth strap and starter connections all in one go.

If the starter really spins up the engine well and she starts, then check out the end terminals of the long cable to the battery and the battery earthing strap and terminals as Barney suggests. Then of course there's the battery itself...

I've been using one 12v battery since I had mine in '97 and it's been fine; mind you it's been changed a few times!

Just a thought, are you using a thick engine oil? This cold weather can then make things very stiff for the starter to crank that engine.

Pete
Pete Tipping

This thread was discussed between 01/02/2007 and 05/02/2007

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