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MG Midget and Sprite Technical - Starter motor ?

Strange one - my battery was quite old and not holding charge and the starter motor was sluggish but fine when engine warmed up.

Just replaced the battery with a new one but starter is better but still sluggish?

The motor is a Moss replacement (new manufacture
when I rebuilt the car and has had little service use)

I’m thinking is it likely rubbish parts again - not working well under load - I think the timing is not far off and when hot starts instantly.

I’m thinking of fitting a spare starter I have (original Lucas) that looks good inside.

I can’t see any obvious corrosion on contacts etc but will try a jump lead from the battery earth to the engine as a check.

Any other ideas ?

Oh ISTR the dizzy has to come out to replace the starter motor?

R.

Think when I get the starter sorted I’ll get it back on a rolling road to check set ups.

R.
richard b

Richard
Maybe check the earth strap engine rear to frame. If OK, might be worth cleaning up the comm on the starter.
Bill Bretherton

Hi Bill,

Just cleaned the battery earth and cut out switch + lead to body.
Will have a look at the engine earth when I finally get underneath the old girl.
If all ok I think I will swap in the old Lucas unit and see - then if it’s better I’ll get a mate I know who’s s good with electrical things to have s look at the Moss one - oh hello Bill !!!

R.
richard b

🤣🤣 I'll have a look at it if needed Richard. Let us know how you get on.
Bill Bretherton

>>>Any other ideas ?<<<

Assuming your setup is the standard Lucas inertial starter with remote, body mounted supply solenoid....
Check for current leakage across the solenoid.
This can go two ways.
Through the solenoid from battery +ve to earth.
Or through the solenoid from battery +ve to output pole to the starter.
The first will drain the battery at a rate consistent with the severity of the leak.
The second will also drain the battery zt a rate consistent with (a) the leak across the solenoid and (b) the leak at the starter itself, and starter motors in general are notorious for current leakage.
Either condition will tend to make the starter appear sluggish owing to voltage drop, and it's natural for this to be worst with a cold engine since a hot engine is easier to spin over and also some heat in the starter and the solenoid may temporarily dry them enough to reduce the loss of isolation.
I suggest using an ammeter to check between the big cable connector on the starter and the battery -ve with the ignition off. If any current is present there is a leak. Next disconnect the big cable between the solenoid and the starter (either end) and repeat the test, but between the solenoid output pole and battery -ve.
If there is no current the problem is the starter. If there is the same current draw the problem is the solenoid. If there is still a significant draw, but less than the first test then both solenoid and starter are leaky.
Which would not surprise me as both are rather exposed and prone to environmental attack.
As an aside, starters and solenoids are a perennial theme for electrical fails on the small fishing boats I work on for exactly the same reasons.
Hope that helps Richard, and good luck.
Greybeard

Another thought - Is this an old issue or only new since playing with the distributor timing-
What static timing or idle speed timing did you end up with---If the initial timing is up too far the starter can seem sluggish, especially cold starting
Maybe try it with the coil disconnected and see if there's an improvement-
William Revit

If you have a battery cut-off switch, it might be worth bypassing it to see if it makes a difference.
Dave O'Neill 2

Grey
Perhaps I have brain fade (!) but I don't see how the ammeter measures starter leakage in the test where starter stays connected - surely you're still only measuring leakage current through the solenoid. And if there IS solenoid leakage to the starter then the starter will take current through its windings anyway? I don't see how you distinguish between starter leakage and its "normal" draw. Obviously you know what you're doing, it must be me misunderstanding!
Bill Bretherton


Bill,
I think Greybeard means putting the cables in circuit with the meter to test for parasitic loads - testing each wire to/from the solenoid.
I don't think I have this issue as I always disconnect when parked up. But worth a check anyway.

Dave

Yes I was thinking that as well, the cut off switch I have is one on the ones with a big green screw that you loosen off to disconnect.
I did clean it but then took it off for a really good going over as its only the bolt that makes contact and I thought it was brass but its only heavily plated zinc.
I have now finally found an original clamp and if still a problem I'll try that.

Willy
I did wonder that and will pull the coil supply and try again, but as it was even the initial turning that was so laboured I'm not sure. - R/R very soon me thinks as carb needle could do with a fine fettling me thinks !

R.
richard b

Richard
Yes I get that but I can't see how you distinguish between starter parasitic and "normal" current I.e. it will draw current ANYWAY if connected to a voltage.
Bill Bretherton

Bill
As I understand Grey's method, it's to check for current draw while the solenoid is not operating
One end of the meter to earth, the other to the starter input should read 0
If there 'is' a current draw then disconnect the main cable from solenoid to starter and retest from earth to solenoid output--if there is no draw there then the problem is in the starter--if there is a draw then it's the solenoid leaking.
Nice one Greybeard, I guess you've found a few waterlogged solenoids/starters using this method, fairly typical of cars that have been for a swim as well- as well as relays full of water.
William Revit

Richard, my left field. OIL.

Engine oil that is.

I had/have the same 'issue'. My Capri was a pig in cold weather. But once the engine was even a little warmed, then much better. The same happens with my Sprite.

I know it's oil, as I took my plugs out to test my thinking. When cold, the engine spins on the starter a lot slower than when warm or in the summer. Definitely a new or recharged battery makes a difference, but even fully charged I still get the same sluggishness when cold.

I find too much advance makes it worse, but gives a slightly different effect; a sort of 'jerkiness' as the engine turns and fires. That's why I pulled my plugs to ellininate both timing and compression.

I use Duckams 20/50, and notice this modern version seems especially viscous when very cold in the cold months.

anamnesis

My apologies for being so unclear. Fortunately Willie was there to point out my daftness!
My method as described is very crude and simple but it has pinpointed the problem many times for me. And as I have said many times, eliminate the simple stuff first.
But I should also apologise for having missed the crucial detail of the battery isolator.
Oops.
As you were chaps, but to me it still looks like V drop from degraded isolation.
Anams point re: cold oil is good too but I think timing is a red herring as hot starting is okay, but it's also an easy thing to eliminate by yanking the LT supply to the coil.
One other point, if you're still seeing battery drain. Do you have a modern stereo in the car? Those wretched contraptions have led me a merry dance many times.
Greybeard

Well I charged the new battery and today with the slightly raised temperature and a spot of sun it cranked quite well and fired immediately.

I’ve booked into Slark’s rolling road for next week so will report back.
Hope I haven’t lost too many horses !!

R.
richard b

This thread was discussed between 09/03/2024 and 18/03/2024

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