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MG MGA - Odd Starter Problem

Hi all,
A little odd this one but one to think about..

My 61 A batteries gave up the ghost (2 x 6V Pos earth) so swapped them out with two new 12V units that fit the cradles.

Alls well for a couple of days till on trying to start the car I heard a high pitched whine and heard bits flying around the engine bay! A quick check revealed that the nut at the end of the starter shaft had come off allowing the starter to disassemble itself.
Unfortunately the end nut had pinged off into the harbour I was parked at (hows that for luck!) so I had to bump start the car.
A quick check showed a new starter was not far off the cost of the bits i needed so I went for new.

Having thought about the cause I assumed that the additional cranking amps had finally put paid to the old starter.

Now I have installed the new starter approximately 50% of the time it fails to engage - just a high pitched whine. When this happens I have to manual rotate the shaft until I can feel the pinion slide in toward the ring gear with my fingers on the starter, then she starts fine.

I have checked the electrical connections and they are fine including the terminal post.

Anything else to check without taking the starter out as that means popping the oil filter off as well which would be a pain as i've just done an oil change!

Cheers

Matt
M Buckland

I did a similar battery mod a few years ago but soon came to the conclusion that the double power was of little, if any advantage. I also found that one of the batteries over time became lazy, with performance dropping off quite quickly. I then fitted isolators to each battery and only ever used one at a time, rotating their use each day. I have since reverted to just one battery and have found I get better battery performance by continually using just the one battery.

Steve
Steve Gyles

I've never ever bought a new starter motor but was wondering whether the manufacturers put grease on the Bendix mechanism to ward off rust in storage and they expect you to clean it off before fitting. It does sound as if you have a sticky Bendix.

(I'm sure you will have connected your 12v units in parallel and not series so won't ask the question!) ..................Mike
m.j. moore

Mike

I resisted asking the same question! I think 24V would have affected more than just the starter motor!

Steve
Steve Gyles

People used to run 6v starters with 12 volts back in the 60s without a lot of problems. Changed solenoid to 12 v. They reckon it made starting very easy. Mike
Mike Ellsmore

Matt
Are you saying you hooked up the batteries in SERIES?
This would be a big mistake.....
I'm hoping that your batteries are in Parallel, and therefor only developing 12Volts, but with double amps...
If that is the case, that's a LOT of amperage, and one battery is plenty, if it is a good battery.
That being said, it sounds like the Bendix is not operating properly....
Remove the starter, and test it with 12V on the bench...
If the starter Bendix does not work, then it is defective....If it does work, then check for a damaged pinion gear, or mis-alignment of the starter...Possibly caused by something on the engine plate or mounting flange, that isn't allowing the starter to properly seat in the hole, and thus will not be perpendicular to the ring gear.
Edward
Edward Wesson 60MGA

A starter is only going to draw the amperage it needs...
Gene Gillam

Gene
That is true...But why have so much amperage that is not needed?....(Also , could be extremely dangerous if a short to ground were to happen).
However, if the batteries are in series, that's twice the voltage, and that WILL burn something out, either immediately, or soon thereafter....
A starter can handle 24 volts for a few short bursts, but you would be overloading the windings, and it will burn out eventually.....You would also be putting 24 volts through the entire electrical system, which would burn out everything else.
I don't even understand why anyone would want two 12V batteries, when one is more than sufficient.
We're not cranking a Cummins Diesel, after all.
Edward
Edward Wesson 60MGA

Edward

Matt did say in his opener about the increased amperage so we should assume the batteries are in parallel. As I mentioned I ran a couple of batteries for a while but could isolate either so I only ran one at the time. I had a spare battery so thought it more useful to carry it in the car rather than leave it on the garage floor. One of those belt and braces mods in case of a battery failure far from home. I have gone full circle and gone back to one battery - probably was not worth the effort with all the extra connections involved with resultant conductivity losses.

Steve
Steve Gyles

Theoretically I think it's a reasonable idea to have two 12 volt batteries in parallel. The main two things that shorten a battery's life are 1. the shorting that happens during starting and 2. leaving it in a state of total or partial discharge for any length of time. A 60 AH battery is not going to like giving out 150 amps or so even for 5 seconds and you can imagine some of the active material on the plates coming adrift whenever the car is started and the plates are heated. The heating effect within the battery during starting will be proportional to the square of the current and I reckon a 120 AH pair will find it four times easier to cope with starting than a single unit. An expensive outlay however!........Mike
m.j. moore

I always keep a trickle charger (Battery Tender brand), with auto-charge feature, plugged into my car (Single 12V Neg ground), when the car is home in the garage....
I do this with my FFR roadster as well....Batteries last much longer, if they don't get fully discharged....(IMHO).
I think a quality trickle charger is one of the best investments you can make for maintenance.
Edward
Edward Wesson 60MGA

This thread was discussed between 18/05/2014 and 20/05/2014

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