Starter motor test

[Keith66]

Hi All

 

Still on going with the electrics and one thing that i didn't do but would be a good idea is bench test my starter motor.

 

Si I stripped it down and cleaned and tidied it up and all looks ok, but i guess i should test it to see if it actaully works.

 

So i'm not 100% sure on how to do that.

 

Clearly i would put a live feed to the top electrical input on the solenoid but i know that won't do much until the White / Red Trace wire from the IGN switch powers and tells the solenoid "GO"

 

So can i use any old live feed for that or does it need to be a specific current to trigger it?

 

Seems sensible to bench test it as i can then see if anything at all is happening.

 

Cheers

 

Keith

[barkerwilliams]

https://www.apexinds.com/blog/basic-bench-testing-starter-motor/

 

Alan

[John Morrison]

10 mins answer,

 

don't you just love this forum!

 

John.

[Keith66]

Thanks Guy's

 

As John say great feedback, someone has almost always had a similar problem, knows how to do something or where the info is.

 

I'll give that method a go and see where we get.

 

Hopefully i'll get something out of it or see if its struggling.

 

Cheers

 

Keith

[Keith66]

Hi All

 

Who knows what about starter motors?

 

I did my bench test and it worked, well kind of.

 

So to be honest on connecting it all up to a newish, fully charged battery off the (cough cough) MG, i was expecting the drive pinion gear to fly out to the end of the housing and spin like billy-o as it attempted to turn a non present flywheel.

 

But not quite.

 

The solenoid kicked in and the pinion gear did fly out pretty fast and turned well abit, well hardly at all really.

 

So the solenoid def works, but the motor seems a bit duff although the bushes seemed ok when i took it all apart to clean it and pretty it all up, but i seem to be getting no motor spin.

 

So any ideas what to check or do.

 

I would rather repair refurb what i've got than simply replace every old item with a new one, although if the motor is US thats what i'll do.

 

Cheers

 

Keith

 

 

 

 

[Mike C]

Vitessesteve has an original Lucas service manual covering their starter motors here:

 

https://app.box.com/s/1grrnsn3ez49a2rlej9h4d5zj87bh1s3

 

I'd make sure the brushes had plenty of length and the springs weren't broken and clean the commutator making sure there was no wiped copper bridging the windings.

 

If the problem is more than that I'd take the starter motor to an auto electrician.

[Keith66]

Cheers Mike

 

I'll have a good read of that.

 

TBH in no electric motor expert but it all looked pretty nice and ok to me. Brushers were around 1cm, which TBH could be good or bad, the springs were fine and hopefully i got it all back together ok.

 

Assuming I'm right and it should spin healthily during a bench test there must be something wrong and if i knew exactly what i was doing i'd know what it was. lol

 

Cheers

 

Keith

Edited August 27, 2018 by Keith66

[Waldi]

Keith,

Yes, it should spin so hard that I stopped testing fearing it would damage the rotor.

Waldi

[rcreweread]

Keith

 

I suspect you need to use a decent sized cable when testing because of the current draw.

 

Just a thought

cheers

Rich

[Keith66]

Hi Rich

 

Yep do agree but i'm pretty sure my cables are ok size wise, see pic.

 

And yep they are as thick as they look being about 1/2 inch diameter.

 

Got from work for use with trucks.

 

So still looking like a motor defect.

 

Cheers

 

Keith

 

 

[Mike C]

The leads look OK- if they're undersized they will get hot while you are trying to crank.

[SeanF]

Keith,

 

Have you painted the edges of the motor casing ie where the black and silver/ally parts butt together (see red arrows on your photo below)? These edges need to be good clean metal as the motor earths through the body and if corroded or painted this will affect the earth.

 

Something to try and worked for me.

 

Sean

[Keith66]

Sean

 

I didn't specifically paint the edges but I'll clean them up anyway, worth a go.

 

But i would hope the earth would be ok via the long through bolts that go from the one end yo the other unless its the black case itself that needs earthing.

 

Thanks

 

Keith

[ed_h]

Hi Keith. Got your PM.

 

The only test that I can think to add is to measure the voltage right at the solenoid when it's energized. Put the ground of the volunteer on the case of the motor. The voltage might drop a little from 12V, but it shouldn't be much. If it drops a lot, and you're sure the battery is good, the motor might have an internal short.

 

If that's OK, measure the voltage on the copper conductor that goes between the solenoid and the motor. It should be essentially the same as the input to the solenoid. If it is much lower, it might indicate a problem with the solenoid contacts.

 

Ed