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MG MGA - Weak Starter

Following on my previous thread when starter wasn’t engaging properly that problem has been solved. Still with an original starter even if body and shaft assemblies come from different starters.

But the starter now seems ‘weak’ as if battery is down on power. The battery seems to be maintaining 13 volts even after lots of starter use and I have felt all the power joints and they all seem cool. I always get started eventually but is a bit nerve wracking.

Can the starter itself have any internal problem that could make starter weak? In my experience starters either work or they don’t, no half way measures, and this one clearly works but weakly. engine is standard early MGB. Any other ideas?

Paul
Paul Dean

Hi

Probably needs a new set of brushes and associated cleaning.

Barry
B Bridgens

I think I might have the answer so ignore until I come back!
Paul Dean

Earth connections?
Nigel Atkins

.....or starter switch.
Steve Gyles

I have checked all connections for heat and I have a new switch which improved things a lot initially over my 60 year old one.
I think Barry is closest but it is the opposite.

Here goes, following my issue reported in earlier post with dog I put a starter together with body from my newish one with the dog problem and shaft assembly from an old one that had probably had failed/worn out brushes. So I think the problem is almost new brushes on a pretty worn commutator hence only making contact around raised edges of commutator.

Solutions. I could take starter out and shave a bit of edge of brushes hence getting contact on main commutator surface. There is a report of someone doing this on MGAguru. But as weather is getting warmer I could live with it for summer and hope brushes bed in and problem solves itself. As I usually just about get enough speed to start eventually I am going to try option 2 for now. Update you in autumn.
Paul Dean

Remove starter and disassemble enough to remove armature. Spin the armature while touching the commutator with a flat file to clean up the commutator bars. Use a knife point to clean out filing swarf from between commutator segments. Oil the bushings, install new brushes, put it back together. Pay attention to the insulator parts around the power input stud where it passes through the end plate. A short to ground there is the number one cause of starter failure.

See tech pages here:
http://mgaguru.com/mgtech/electric/ss_110.htm
http://mgaguru.com/mgtech/electric/ss_112.htm
http://mgaguru.com/mgtech/electric/ss_114.htm
Barney Gaylord

Paul,

Went through this exact situation a few months ago.

Checked all connections and even put in a new starter switch while at it. No real improvement.

One day it appeared completely dead. Tried tapping it with a wrench while I hit the starter and Voila!

New one with shipping was only about $100, and it solved the problem completely.

Best,

- Ken
KR Doris

Now back from my week's holiday in Scottish Islands, not in MG unfortunately.

I have just been measuring voltages with the following results.

Battery with no load is 12.9V despite car not hav9ng been used for a couple of weeks.


Batttery when stater pulled, ignition off, reads about 10.8V. Does this suggest weak but not failed battery?

Starter side of starter switch is 9.8V and battery sideo of switch is very similar.

These results probably are reason for starter being a bit slow. They also suggest new Moss starter switch is not a problem. By the way I can't detect any heating up in any of the connections including engine earth.

Any comments or suggestions?

Paul
Paul Dean

9V-10V is a normal voltage while cranking
Your 12.9V after sitting that long is possibly a tiddle higher than I'd expect, maybe 12.5V so your voltmeter might be a touch out/high but even then if it is out you'd still have 9.5V cranking---all ok, seems normal
Clean up all them battery and lead connections and if that doesn't improve things it must be the limited brush contact doing it

willy
William Revit

Paul. While I respect Willy's significant body of knowledge, I would have to disagree that a voltage of under 10 volts is nor a problem. Most of the ones I have checked have been in the 11-12 volt range with good cables and a good working starter.

So, "good cables and a good working starter". You have done a lot of work on your starter, but have you been able to have it tested on some form of test machine? These are so common in the US that ever parts store has one and will test your starter or alternator for free in hopes of selling you a new one either after testing or later if the unit tests good. Bench checking is not a bad idea, but for the hobbyist, mainly means securing it to a bench and applying power to ensure it turns over. Useful in that you know that it spins and can see if that is excessively slow, but not as good as a test machine which will put the starter under load.

A commonly missed area is the cables, especially the long one running from the battery (batteries) forwards to the starter solenoid. With the voltages you are showing, I would do the following:

1. Check and confirm the voltage at the starter itself. Make a note of it.
2. While cranking, check the voltage at the battery (batteries) and note it. It should not drop much below 11.5 volts if the battery is good.

Depending on what you find, clean all of the battery terminals and all of the cable's terminal clamps, the reassemble and test again. If the cleaning helps, good. If the voltage at the battery remains high and the voltage at the starter remains low, hook up a long jumper cable from the negative terminal of the battery (if the vehicle is still positive ground) to the starter solenoid and try to start the car. If it works better, replace the old cables which, over the years, get corrosion inside and lose the ability to carry full voltage under load.

Hope this helps. Les
Les Bengtson

Cheers Les--need to lift my game a bit--
Something I missed in Paul's last post was the battery voltage cranking--10.8V and
voltage on both sides of starter switch--9.8V
Losing 1V between the battery and the input to the switch needs sorting out as you suggest---Dirty terminal connections on battery or switch or both--?--or faulty cable
William Revit

Great news problem solved by buying a new starter that is dramatically better than the previous new ones from Moss.

Firstly the starter saga started when my very well used one failed about 3 years ago after being on car for 60 years, probably due to worn out brushes. Anyhow with new starters being so cheap I decided to buy an new one. Th first one was so weak that I sent it back but while the replacemnt seemed acceptable in summer it was always pretty weak in winter but then it failed completely by the bendix failing to engage properly and wrecked its cog. I had a couple of other dead starters and using the 3 year old Moss ones with the shaft/bendix from one of the old ones I got one that worked but this was still too weak.

THE GOOD NEWS. Thinking I had wasted enough time I decided with some reluctance from previous experience to buy another one. The big difference was I went to a local supplier (Chic Doig Classic sport cars) and when I fitted this WOW the 1800 engine burst into live. It was night and day better than the Moss ones. Colyn Firth said he had no problem starting his 1950 engine with a standard starter well I now believe him but you have to have a quality starter not one of the rubbish ones

It is made by a company called Prestolite Electrical Heavy Duty Syatems who are an American company with their European HQ in Greenford who basically specialise in worldwide manufacturer of starters and alternators presumably to car manufacturers.

Thanking for all the effort on checking out wiring. My readings are now:-

Battery No Load - 13
Battery Starting - 11
Starter when Starting - 10.2

Thanks for all the help, but main message is you have to get the right replavemnt starter!

Cheers

Paul

Paul Dean

By the way Dingbro, whose red vans you see everywhere delivering parts to garages, are distributors for Prestolite so if you want one a local garage should be able to get you one. I can give model number.
Paul Dean

Thanks for reporting back.

Unfortunately it's the old story of poor quality modern made parts being sold by suppliers, mainly because most classic owners want the lowest prices and notice less about the quality as they use their classics so infrequently and rarely.

You paid a very high rental cost to Moss for your starters and had a load of hassle from the poor quality parts.

ETA: Perhaps the suppliers such as Moss and others should be told about the likes of 'Prestolite electric' but I expect you're the first customer to have had this problem with this part. 🤣
Nigel Atkins

I can confirm the poor quality of some new units. One I fitted to a twin cam failed within 100km and three starting attempts - and it is a LOT harder to get one into a TC than a pushrod car.
Dominic Clancy

This thread was discussed between 11/05/2021 and 07/06/2021

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