Rebuilt starter motor woes

[Rigid]

I took my starter motor off to investigate an occasional 'starter click'.
First thing - unbolt the solenoid and clean-up the heavy duty contacts within.
When removing it I made the mistake of pulling the solenoid inner off of the pivot.
After failing to refit it in-situ I took the motor out - seemed a good idea since I could hear a good 'clunk' even when suffering the 'click'.

Looking at the motor brushes - at least one was getting short so bought and replaced all 4.

Since then I've proved the motor runs nicely on the bench with 12V on the appropriate contact and -ve on the body.
BUT - when I reinstall it into the car I can't get it to work.
It spins but with a rat-a-tat-tat machine gun noise as though the bendix cog isn't engaging correctly with the flywheel gear, or is it something inside the motor?

HELP!

[Lingen]

Rigid. If you put the headlamps on when you try the starter, do they stay steady or go dim? If they are affected I would check the battery terminals. If they stay bright, then check the engine earth strap from the battery to the timing chain cover. If that makes no difference, then I think it may be a poor connection at the starter motor -including the earth.
Mike.

[flying farmer]

Bad connection, as the starter engages and draws current the voltage drop is sufficient to disengage the solenoid. Voltage then rises and the solenoid pulls in again, repeats until you release the key

[Rigid]

Thanks guys.
I can test both of these with a jump lead between the starter and the engine or battery.

I’m getting very good at fitting and removing the motor - got it down to less than 5 mins each way. 😀

[trunt]

Im with Lingen, the engine ground strap.. Recently had this on my sons MGB found it by looking at starter cranking voltage with meter using engine ground which went down to 7v then used battery ground for the meter and it was 12v — loose bolt on the strap.

[Rigid]

Update (note - not necessarily progress)
SM reinstalled onto car with a jumper cable clamped onto the battery -ve and the SM flange - still the rattly noise.
Headlights on - no change in brightness.
Checked the timing chain cover connector - all tight, no sign of it having ever moved or been disturbed.

Took it off again and checked it inside.

Back together and wired up but supported beneath the car on a toolbox so no teeth to engage - everything whiring and spinning correctly.
Even checked that the Bendex was spinning the cog in and out - all good.

Back onto the car.
A rattling attempt but then a good one, then a click.
Then click, click, click etc.

It was as if the SM cog just couldn't engage with the starter ring until it did.

I've given up for tonight with the battery back on charge to ensure I haven't just drained it.

[Goldstar]

Long shot but could the teeth on your flywheel be the problem?

[Rigid]

1 week later - still mucking about trying to get the starter working.

Everything has been apart again.
I've cleaned the oil from under the Bendex cog - I'd put some 3in1 on to help it but then decided it could be slowing down the throw due to surface tension.
This will be replaced with pencil lead - graphite is a dry lubricant.

I read that another user had added lead-free solder to the faces of the big solenoid contacts to help keep them true so I've given that a go too - I was energetic when originally smoothing them when first dismantled so we'll see if that does anything.

The most recent starting attempts still sounds like rhythmic knocking/grinding/banging but with the ocassional correct whirring - so progress.

I've measured the distances from the motor mounting faces - the flywheel starts at 17mm, the pinion cog starts about 18mm in.
Does this not mean that they are always interfering?
Were Stag starters ever fitted with shims to space them out?

Note - the motor is a 2M100 / 25647J - so an early MkI version.
The Repair Manual doesn't show this type - ie it has no adjustment pinion but is there anything special needed for my version?
The Parts Manual doesn't even list this version but that doesn't worry me, my gearbox is secured using the large saloon mounting not the cotton reel mounts even though the gearbox is appropriately numbered LD2076 for the chassis number.

BTW - I can remove a starter motor in 3 minutes - is this a record?

[Philip Wardle]

Not sure if this Lucas workshop instruction will be of any help? Apologies if you already have it.

2M100PE_issue1.pdf

[Rigid]

Thanks Philip, not seen that before.
It looks like I've got most of it right but...

I've tried everything I can think of and have totally run out of ideas.
I'm not used to giving up on mechanical things but this has beaten me - it was working but with the ocassional click - when I took it off the car.
Now the solenoid activates and the motor spins every time, it just wont mesh properly with the flywheel.
Time to hit the catalogues and spend some hard earned on a new one.

[Lingen]

I may have missed this, but have to tested the output voltage of the solenoid when it is activated?
Mike.

[Rigid]

Hi Mike.
No not measured the voltage yet.
Are you thinking the starter might be dropping out and disengaging the pinion then re-engaging them dropping out etc. etc. ?

[Lingen]

Yes! And this usually happens whet there is insufficient current = amps to keep the solenoid closed and the starter energised.
Mike.

[flying farmer]

Have you actually tried a drop test on the battery, it could be that a cell has died and is supplying voltage but cannot supply current.
I had one that did that, and with the caps removed from the cells one cell could be seen to be boiling under the load from the starter motor. It was fine one day and the next it was knackered

[Rigid]

Final update.
Thanks to everyone for their input and advice.
The WOSP starter arrived from EJ Ward today - without installation instructions!
Thanks to the search function on the forum I worked out that this assembly only uses the fatter Red/White cable and the BIG black +ve.
All fitted, tested and one quick Autumn blast later I woe no more.
(still don't fully understand why my refurb of the original motor didn't want to play)

Quick blast revealed a non-funtioning indicator self-cancel but at least fixing that doesn't involve crawing under the car.

Thanks again.
Richard