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Starter Motor gremlins


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Hi,

I need some help diagnosing a starter motor problem and finding a solution:

 

The ignition key spins the starter motor but the engine doesn't turn. The problem started a few weeks ago, I removed the started motor, I say removed but actually undid the two securing bolts and and withdrew it as far as possible to find I couldn't remove it from the engine bay so put it back in and secured the bolts. The problem went away however it has now returned.

 

Can anyone advise what the problem may be, it isn't a flat battery, and a solution and if it requires removal of the starter motor from the car can this be done without dismantling others parts to allow removal?

 

Kevin

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Hi Kevin, sounds to me like the gear is siezed on the shaft. This gear is thrown in to the fly wheel ring gear in the first moment the starter motor is engaged. These grooves usually get clogged up with dried engine oil and dust from clutch stopping it from engaging and just spinning without turning the engine over, assuming it has not been sitting for a while and rusted. I've never removed mine, but it does look tight. The pinion might be cleaned up in a suitable degreaser, used petrol when I was a lad. Don't lubricate it when it's clean before you put it back, it needs to be dry, otherwise it wont be long before you are back in the same boat

 

Sounds like it needs to come out for inspection, could also be worn teeth on ring gear or starter pinion.

 

Mark

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As above - although I would say 'sticking' rather than seized.

Just needs cleaning, although that means removal.

 

AlanR

Hi Alan, yes sticking is a much better description than siezed in hindsight, as it is easily freedup.

 

Mark

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Kevin,

When you get the starter in your hands and know what you might need in spares PM me as I have a selection of NOS Lucas starter spares, from brushes to bushes to armatures to fields to bendix gears. I think there is a rebuilt Lucas TR4 starter in the stocks too.

 

This stock is from the years that my father rebuilt Lucas electrical units for a living.

 

Cheers

Peter W

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Peter.

 

If you have any NOS rubber shock absorbing drives for the old "Bomb" style motors I would interested in grabbing one as a spare,

as in my 1970's experience of these it was always that item which would fail.

 

Bob.

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Peter.

 

If you have any NOS rubber shock absorbing drives for the old "Bomb" style motors I would interested in grabbing one as a spare,

as in my 1970's experience of these it was always that item which would fail.

 

Bob.

Bob,

Will check this morning for you.

Peter W

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Kevin,

I think that the TR4 began life with an inertia-engaged starter, although I see that pre-engaged, 'Hi-Torque' starters are sold for that model.

If yours is just a single cylinder, its the first, if it has a smaller cylinder on top of the main one, its the second.

The way that these make the pinion, the small cog on the motor shaft, engage with the starter is different .

 

The "inertia-engaged" starter uses a "Bendix drive" in which the shaft has a spiral thread between it and the pinion, so that when it starts to spin, the cog is thrust away from the motor by inertia, pushing it into gear with the ring.

.This action can stick, due to an accumulation of clutch dust and dirt

As said above, once you have the motor in your hands ( and it's a fiddly job to get it out) you will see the Bendix.

Clean it and the helical drive with brake cleaner, until is moves freely. The lubricate it, NOT with grease or oil, but with graphite powder.

Available online, eBay etc, or whittle down a soft pencil!

Grease will just attract more dust.

 

A 'pre-engaged' starter uses a solenoid in the starter - that second cylinder - to push the pinion into gear.

If that has failed, then it's a new or reconditioned motor.

 

Hope that helps. Hundreds of Google hits about these if my words are not clear.

John

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The "inertia-engaged" starter uses a "Bendix drive" in which the shaft has a spiral thread between it and the pinion, so that when it starts to spin, the cog is thrust away from the motor by inertia, pushing it into gear with the ring.

On the old "Bomb" style motors (Tr2,3,3A ect.) This is correct, but for a TR4 the motor is different, in that the shaft with the bendix on it extends beyond the flywheel, & when the starter is powered up the bendix action pulls the gear towards the starter motor, & engages with the rear face of the flywheel ring gear.

 

Bob.

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Many thanks for all the helpful posts.

 

Bob (Lebro), you are correct in your description that the gear sits to the rear of the clutch at rest and moves forwards towards the motor body to engage the flywheel. When partially removed previously everything seemed to move easily. I guess I need to check again.

 

John.r.davies - are you saying it can be removed from the engine bay without removing other components - its just very fiddly or are you saying its fiddly because other components need to be removed?

I am away this week so will be attempting the fix next weekend and will keep you all posted.

 

Kevin

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It's always fiddly, and it went in so it must come out, but you need the advice of a TR4 owner!

 

And I bow to Lebro's superior knowledge of the TR4, but the principle is the same.

 

JOhn

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Kevin, I replaced the original Lucas M418G starter motor on my 4A with a high torque type some years ago and haven't looked back. I think the 4 and 4A set ups are identical and whilst there may be differences car to car I found it necessary to disconnect the upper flexible coupling and move the steering column to one side in order to manoeuvre the old starter motor out of the engine compartment. I also found powdered graphite an excellent lubricant for the clean and dry pinion assembly.

 

Tim

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Its fixed! Tried to take the motor our without removing anything else, it just wouldn't happen. While still in the engine bay the bendix was stuck at the end of its movement. By the time I had disconnected the steering column and removed it it was free. Nothing else needs to be disconnected but removal is still very tight. Couldn't see anything to cause the problem but gave it a good clean and put some graphite on it.

 

Thanks to all for the words of wisdom.

 

Kevin

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At least you have witnessed the bendix being stuck prior to removing the motor even if it did "fix" its self.

You need to repeat the exercise, but this time completely dismantle the bendix part of the motor to find out what is the cause.

 

Bob.

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Bendix has been taken apart and the problem revealed: it appears there is too much play in the components on the shaft so that the collar/washer that the spring sits in (end away from motor housing) is getting caught between the part that slides up and down the shaft with the thread on the outside and the collar that sits at the other end of the shaft (motor end) that the spring sits over.

 

There is no adjustment and everything is kept on the shaft with a circlip. I have a Haynes manual that shows a nut that takes a split pin which would obviously allow for adjustment. There is only a circlip.

 

Is the solution to add a washer to the circlip end of the shaft?

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Kevin.

I have studied the exploded diagram of the M.418G motor in my TR4 Workshop manual. you are right, the book does show a slotted nut, with split pin, which you can clearly adjust to sandwich everything together. In your case yes your suggestion of adding a spacing washer under the circlip will probably work. You need to have no gaps between the spring collar, The "screwed sleeve", thrust washer, big spring, & end fixing - in your case circlip + washer(s).

Maybe the big spring has relaxed over the years, & got a bit shorter ??

 

Good luck

Bob.

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Should the big spring be compressed to get all he components on the shaft?

 

A washer on the end of the shaft will not work as the circlip sits half in the shaft and half in the disc on the end, a washer would try to shear the circlip.

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Her is a diagram from the Rimmers site, it shows both options of end fixing.

 

http://www.rimmerbros.co.uk/ProductImages/XLarge/GRID200518.jpg

 

It is not clear hoe the circlip option actualy works, & I have never seen one.

I would say that the big spring should be compressed, but by how much not sure.

Can you put a spacing washer elsewhere (say at the other end of the assy) to take up the slack?

 

Bob

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Should the big spring be compressed to get all he components on the shaft?

 

A washer on the end of the shaft will not work as the circlip sits half in the shaft and half in the disc on the end, a washer would try to shear the circlip.

You need a screw clamp to get the circlip and retaining washer off the shaft - It's called a bendix compressor.

Overall end float of the shaft is controlled by internal shims bearing against the end plates. You are looking for 5 thou ish. New

I have some NOS bendix units - how many teeth has yours? Plus a quantity of other spares to build that type of starter.

Cheers

Peter W

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Suggest you check that nothing has gone missing from the assembly (check against the exploded view), or that one of the parts (spacers, collars etc) have not worn to the point that they are not doing their job. I agree that the big spring should be under a fair amount of pre-compression.

 

Bob.

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