Sluggish starter motor

[bullstreetboy]

Guys

 

When the engine is cold and I push the start button the motor turns but very slowly and sometimes stops as if the engine was hydraulicing. The engine is not loosing water or using oil.

 

It did it with an old starter motor and now does it with a professionally refurbished starter.

 

So it seems to me it may be an engine earthing problem. Should there be an engine earthing strap somewhere?

Edited September 7, 2015 by bullstreetboy

[Lebro]

Yes. usually between the top, & bottom of the left hand engine mounting. This connects the engine to the chassis, you also need a good connection between the chassis & the body, this is normally obtained through the many body attachment points, but you can always add another if required. Finaly the battery cables must make good contact to the body, & on the other side the starter solenoid, & of course from the solenoid to the motor.

If all of these are good low resistance connections, (and you have a decent battery) then the engine should spin over quickly even when cold.

 

Bob.

[Don Elliott]

Here is the ground strap on my 1958TR3A. It is secured at the front of the engine down to the frame stud for the engine mount on the left side. Don't attach it where the rubber block in the engine mount will prevent the connection.

[bullstreetboy]

Thanks Guys

 

So I am missing an earth strap

[RogerH]

As mentioned earlier do not just rely on the basic straps fitted as original. Put an extra strap direct from the battery to the engine.

 

Battery to body - make sure there is NO paint under thevearth braid

Chassis to engine - again make sure there is NO paint under the contacts.

 

And

 

Battery to engine direct.

 

Roger

[Ian Vincent]

You don't need to have a strap from battery to engine direct - at least I don't have one and my starter works well. I do however have a good strap between the engine and chassis and from chassis to body. Also as Roger says clean off the paint underneath. I had some left over code 4 lead from a building project that I used to make lead washers to go between the strap and the bare metal on the body or chassis at each point of contact. This has two advantages, it gives you a good connection and prevents the bare steel rusting.

 

Rgds Ian

[Lebro]

+1 I don't have a direct link to engine either, but all other connections must be 100%

 

Bob.

[bullstreetboy]

Guys

 

No progress on this.

 

New battery fitted(the existing was 5 years old) - no change. Both batteries gave a voltage of approx. 9.4 across battery terminal on load and the same at starter motor terminal.

 

I haven't checked the engine/chassis earth strap for resistance - yes it does exist,

 

So it seems to me that my re-furbished motor may have become NFG. I do this have the original that had a Bendix problem.

 

"Battery to engine direct" - OK but not authentic, but mines running twin 40's!

 

So BEFORE I crawl under the car on my back with the wheel on ramps, at the age of 68 - I don't relish the thought, have you Guys go any other suggestions.

Edited September 24, 2015 by bullstreetboy

[bob-menhennett]

What state are your main battery cables,clamps, solenoid connections, starter motor main cable and connections....all in good condition and squeaky clean ( as in ...freshly rubbed down to clean metal) ?

As others have mentioned if the " route " suffers along the way , for whatever reason you will see a voltage drop.

Bob

[Kiwifrog]

Run a Jump lead straight from the battry earth connection to the engine to rule out earthing problem

 

cheers

 

Alan

[RobH]

You don't really give many facts to go on with your question. Does it turn over OK when hot? Is this a new thing and did it follow any work carried out on the engine? Did it always happen with the old starter? Could the deranged bendix have damaged the ring gear?

[Rodbr]

Quote" the motor turns but very slowly and sometimes stops as if the engine was hydraulicing"

 

I would suggest that it might be worth checking ignition timing as too much advance could give similar and slow engine turning.

Worth checking for ilimination purposes.

 

As said, difficult to advise without more info i.e what has changed.

Any symptoms prior to this?

[RogerH]

Hi BSB,

remove the plugs and see if it turns better - this would prove ignition timing (maybe).

 

 

Ian,

although you have no direct battery to Engine cable you have actually simulated it with the layout you have - three earth straps.

The original was battery to body and chassis to engine - two earth straps.

 

The body to chassis relied totally upon the body mounting bolts to penetrate the paintwork wherever they were. This would not always/reliably happen is decent washers etc were used.

 

Roger

[bullstreetboy]

Guys

 

Thanks for all the advice. When I could start the engine, when it was hot it turned over faster. I'll try a jump lead from the negative to the engine direct to rulke out earthing problems. Since I have 9.6V across the terminals under load and the same at the starter motor, implies to me that I don't have connector/cable etc problems. BUT 9.6v is borderline as I understand it. In retrospect I think the problem has been getting worse with time. This motor has been on for about 3 years now so I don't think there is damage to the ring gear - that would have shown up straight way. The old one was changed because it would not engage most of the time.

 

I think I have to accept that I've got to crawl under the car and remove the motor and check it on the bench. As I recall I have to drop the exhaust from the manifolds?

[RobH]

If you still have the original setup does the engine turn over easily using the starting handle, with the plugs out ?

 

If the connections are OK and the volts you have measured is across the motor then the starter must be pulling sufficient current else the battery volts would not drop so far, so the motor brushes and armature are probably good. There might be a fault in the field winding though which would result in weak torque.

[bullstreetboy]

I fitted an aluminium radiator so don't have a starter hand hole anymore. I think you may be right with a fault in the field winding. My plan is to remove the motor , change the Bendix to the old motor and try again.

[RogerH]

Hi BSB,

I know this would be moving the goal posts a bit but with the starter motor off have you considered fitting a Hi-Torque motor.

 

Much smaller, so easier to fit and they do spin well.

 

Roger

[bullstreetboy]

Roger

 

re hi torque, I wish!

 

Tries the jump lead from -ve direct to engine - same thing.

 

BUT then NOTHING - starter motor does not even attempt to turn. 12.6V at terminals and 12.6V at starter terminal. So, given my rudimentary electronics, I'm thinking my re-furbished starter motor has gone NFG.

 

Time to get these aching bones under the car again.

[BlueTR3A-5EKT]

 

Can you turn the motor 1/2 turn by the square on the shaft end that sticks out the front? Do so and retry to start. It may be a flat or burnt commutator bar. Rotating to a 'better' contact area may solve this issue once. Could also be a loose or not properly sprung carbon brush. That can be checked through the motor casing side

I have a lot of NOS spares for these motors.

Cheers.

Peter W

[Kiwifrog]

Its very common for the bush at the starter to wear out which will give exactly the symptoms you describe

 

part 70 on the moss web site

 

http://www.moss-europe.co.uk/media/catalog/product/cache/1/image/1900x/ea1221f5636c5afbfbab23a8a05a623f/t/r/tr24_16_11_01.jpg

[RogerH]

...or even for the bush to fall out completely....

 

 

 

Roger

[bullstreetboy]

Guys

 

The motor is out on the bench for inspection after a beer or two. I could turn the motor by the spare drive at the back. The motor was completely dead and not pulling any current at all.

 

I like the workshop manual instructions:- "undo two bolts and remove the motor from the engine compartment!" Ye right! I did have to drop the exhaust from the manifold and then it was still a very tight fit.

 

I'll post again when I find the cause.

[bullstreetboy]

Guys

 

The motor is now running fine on the bench after removing all 3 brushes and removing burs from the face and honing the sides. One bush was sitting a lot higher than the other two!

 

Should I apply any lubricant to the bushes?

 

If body ache will allow I'll reverse today and let you know.

[RogerH]

You shouldn't need any lubricant on the brushes.

 

Roger

[BlueTR3A-5EKT]

Do you mean carbon brushes - I have always thought there were 4 brushes in a starter motor?

 

As Roger says no lubricant needed.

 

Is the commutator round and have a clean flat surface that the brushes run on? - could cause slow running if not.

Are the field coils in the casing oil soaked, and do they smell burnt? - could be an issue with shorting.

Are the bronze bushes in each end of the casings a good tight running fit on the shaft? - Will allow the shaft (armature) to wobble and bounce the brushes off the commutator when running, causing arcing, burning and slow running.

 

Cheers

Peter W