testing a starter motor off the vehicle

[eltax91]

Hi guys

I have a defender 90 as an off road toy. It turns very slowly, or clicks when I turn the key. I have fitted a new battery today, to no effect. I suspect it has mud/ damp in there and the cold weather has hardened this and made it ineffective. It looks easy to get off, so I will have a go tomorrow. Threads online suggest 'whacking it' to break up the grime, and trying to get degreaser inside somehow.

My question, rather than having to continually refit it to see if I have managed to fix it, is there a way to test its function on the bench? I have a known good battery, jump leads and a few bits of old battery cable I can make use of.

So, how would one wire it up to test solenoid and turning action on the bench?

Cheers

[shovelheadrob]

Just connect the neg of battery to the starter body, the pos to the terminal of the solenoid that you removed the large pos feed from when you removed the starter, then bridge from this terminal to the small terminal on the solenoid. make sure you have a good hold of the motor, maybe clamp it in a vice or stand on it, as there is a fair bit of torque reaction which will show itself if it is working.
I am assuming it is a pre engage type starter & not an old inertia type as they only have one terminal

[Nealio]

battery negative to starter body. battery positive to screw down terminal on starter.

To activate it bridge the positive terminal to the other little terminal (possibly a blade connector). Have your foot on it.

[jonnynine11]

Jump leads as follows: earth to body of starter motor. Positive to main terminal on solenoid, this will throw out the gear. Then open the jaws of the jumplead so it touches the trigger wire and this will spin the motor.

[interloper]

Be aware, testing it off the vehicle with jump leads is easy but flawed. Just because the starter spins doesn't mean it has enough oomph to actually turn an engine over. learnt this from bitter experience!

[eltax91]

Cheers for the tips chaps. I have a vice so will clamp in down first! Wish me luck!

[eltax91]

interloper said:

Be aware, testing it off the vehicle with jump leads is easy but flawed. Just because the starter spins doesn't mean it has enough oomph to actually turn an engine over. learnt this from bitter experience!

A fair point. I plan to test is straight out of the truck to try to asses its effectiveness, then try to clean it, whack it and spray it., then retest to see if it appears to be running any better before I try it on the truck.

[mobile chicane22]

could posibly be an earth fault try putting a decent jump lead from the battery negative to somwhere on the engine block near the starter

[eltax91]

mobile chicane22 said:

could posibly be an earth fault try putting a decent jump lead from the battery negative to somwhere on the engine block near the starter

Tried that already. No luck.

[wolf1]

Find where the earth lead from the battery is bolted to the chassis, remove it and clean it up with emery paper, do the same to the chassis. Next find the earth from the chassis to the engine, do the same as you did to the other one. Then do the same to the positive from the battery to the starter motor. If that doesn't do it then grab a multimeter and post here and I'll go through how to test for voltage drop.

[Nigel Worc's]

It could also be a bearing siezing up, but that'll become obvious when you have it on the bench.

[eltax91]

Hi guys

Finally got the starter away from the vehicle! So 5 hours of fighting!!

It's a typical starter type, with a main body, and a smaller solenoid on top. The solenoid has a pole connector and a blade. The main starter has just a screw-on pole connector.

So, wired up:-

Negative to one of the main mounting screw holes on the starter body
Positive to solenoid "pole"
Small wire from Solenoid "pole" to little blade - starter engages/ disengages as expected.

So, what do I do to test in spins?

This is to "benchmark" it, before I strip it down and tyry to clean it up, prior to attempting a refit. Altough, with the difficulty I had removing it, I may just replace it!!

Cheers

[eltax91]

Ah, just "held" the wire to the blade connector and the starter spins. Albeit very slowly, then dies. Got the battery on charge as it's been sat a day or two!

So, it span, but not with enough torque to "jump" as indicated!!

So, does this indicate it's goosed?

[jjones]

so it hardly spins with no load then there's a fair chance its fked. i would use another car and put it on the floor, attach jumpers and see if performance is any better from the known good battery (as above put foot on it to secure it - mind toes on the teeth )

[eltax91]

well, I went back out to the garage (to the disgruntlement of SWMBO), with the freshly charged battery, and a similar story, it spins up, then slowly dies away, then just a flurry of sparks

Time for a new starter I think, which is a shame, as it's £100 just to get it all muddy again and for it to break... again! Oh well, the perils of off roading.

[shovelheadrob]

You don't need to get a new starter, it could be as simple as a new set of brushes. A good auto electrician should be able to sort it out for a fair bit less.