Testing a starter motor off the vehicle

[mangocrazy]

I'm laboriously getting a refurbished motor ready to take to France to substitute for the broken one, and I'm now ready to re-fit the starter motor. Before I do, are there any checks I can perform on the bench to see if the starter motor that was fitted to the engine (which has no known provenance) is viable or not? I was thinking of clamping it in the vice and then running leads from a battery to the +ve and -ve terminals. Is this wise or worthwhile? And how do I tell which starter motor terminal is +ve and which is -ve?

Given that it's in a particularly inaccessible area when the engine is in the car, I don't really want to find out I have a duffer when I come to start the motor for the first time.

[gengis]

Yes that would be a worth while test.

Clamp starter in vice, connect +ve lead to the vacant terminal on the solenoid usually a M8 copper coloured stud.  Then connect the -ve lead to the casing of the starter, next use a smaller wire with croc clips from the +ve solenoid (heavy croc clip) to the spade terminal of the solenoid.  This will then energise the solenoid which will switch the main +ve current through to the starter making it spin if it's a good un.  This will also check that the solenoid is working correctly.  I would also give a drop of oil to the end bearings and the bendix shaft.

Please make sure the battery leads are kept isolated from each other during this process. THERE IS A LOT OF ENERGY IN A BATTERY.

[lukasdeopalenica]

I would suggest also checking condition of the starter brushes when you have it out. Access to them you will gain after removing of a back cover.

[mangocrazy]

My starter motor solenoid has two contact posts, both with an M8 copper thread. The top one has no obvious connection (other than an internal one, I guess), the lower one has a lead attached which heads off inside the starter motor. Which one should I connect to the +ve terminal on the battery, and which one to the -ve? There is also a small lead with a spade terminal on it that is soldered on to a connection somewhere between the two M8 threads that is flopping about loose.

I tried connecting battery +ve to 'top' connection and -ve to 'bottom' connection and was met with deafening silence. Excuse my numptyness with electrics, but I don't want to do something silly and bugger it up. What should connect to what?

[gengis]

Please see picture... -ve lead goes to the metal casing of the starter, +ve lead to the outboard heavy terminal of the solenoid.  The small lead clips onto the spade connection, then dab on to the heavy +ve lead to energise the solenoid switching the battery supply through to the starter motor itself.  Hope that helps.

[mangocrazy]

Excellent stuff - many thanks! A picture is certainly worth a thousand words in this instance...!

[mangocrazy]

Yup, that works a treat. I was only using a 12Ah motorcycle battery for the test, but as soon as I touched the fly lead to the +ve solenoid terminal the starter whizzed around and flung the pinion down its shaft. Quite made me jump the first time I did it...

Tomorrow I'll inspect the brushes, but from what I've seen I'll be quite happy to bolt that starter motor back onto the engine.

Thanks again, gengis...