Proper way to bench-test starter?

ShaunBlake · Sep 3, 2015

My procedure for testing starter is:
1) Clamp or fastern to bench;
2) Clamp negative battery cable to frame of starter;
3) Run jumper to starter terminal;
4) Touch positive battery cable to solenoid post;
5) Smile when solenoid engages and starter spins.

What am I missing?

Thanks!

100 td · Sep 3, 2015

Nice, but it doesn't load test it!
Then while its running get a long piece of 4 x 2 and lever between the bench and the starter drive gear and chew the shit out of the wood, simulating a decent load onto the drive gear. This proves the planetries and clutch if it has them, and load tests the windings to ensure it has some grunt to turn your engine over.
While you have it out, check your brushes, and lubricate the bushes/bearings/pinion. The solenoid has 2 coils, one is the pull-in coil and one is the hold-in coil. The hold-in is low current and pull-in high current. The pull-in circuit goes thru the brushes and armature to ground, when you have a worn or sticky brush and your starter goes CLICK, CLICK, but nothing happens when you try to start, the reason, your low current hold-in coil is trying to engage the starter and solenoid, but can't because it's not strong enough to pull in. There is no circuit to the pull-in coil thru the brushes and armature. So when you belt the starter with a hammer and it starts, you have made the brush make contact with the armature and the pull-in coil now works and engages the starter.

olthumpa · Sep 3, 2015

ShaunBlake said:
My procedure for testing starter is:
1) Clamp or fastern to bench;
2) Clamp negative battery cable to frame of starter;
3) Run jumper to starter terminal;
4) Touch positive battery cable to solenoid post;
5) Smile when solenoid engages and starter spins.

What am I missing?

Thanks!

Attach other end of jumper cables to good battery.

Is it possible for you to bypass the solenoid and go direct to the starter? I know that some starters you can and some you can not. It could be a bad solenoid.

Good luck!

ShaunBlake · Sep 4, 2015

Update: Proper way to bench-test starter?

With the starter clamped to a bench and using a hot battery, with jumper cable negative clamped to frame of starter tested by:
1) clamping positive to B terminal, jumping from positive to S terminal;
2) touching positive to S terminal;
3) touching positive to ? (post for starter fields).

Nada. Maybe a tiny bit of sparking. (Accidentally bumped the positive to the starter body and got a very hot spark.)

<sigh> I'm torn between just buying a new starter and trying to refurbish this one, which seems to have a shot solenoid as well as a broken field. Bank account says, "do the dirty thing".

Jim L. · Sep 4, 2015

Shaun

Can you read the manufacturer and model from the starter?

Maybe we can find a rebuild kit.

100 td · Sep 4, 2015

Pull the end off and check the brushes and commutator.

100 td · Sep 4, 2015

As starter motors are generally series wound motors, the field winding is in series with the armature, so if a brush is worn or stuck and not contacting the commutator then there is no circuit in the field winding. So you need everything to be good for it to work, field winding, brushes and armature winding. Most common cause that interrupts the circuit - brushes and commutator. And as mentioned previously, the pull-in circuit of the solenoid goes thru the starter motor circuit thru the brushes to ground.

Jim L. · Sep 6, 2015

100 td, your suggestion is brilliant.

While not Shaun's model, my L3800 lists a starter at US$677. I realize that there are other options for much less.

The brushes list at $2 each. With a little work those starters don't have to be scrapped.

ShaunBlake · Sep 6, 2015

Jim L. said:
100 td, your suggestion is brilliant.

While not Shaun's model, my L3800 lists a starter at US$677. I realize that there are other options for much less.

The brushes list at $2 each. With a little work those starters don't have to be scrapped.

<gasp><choke>

I priced one for the B6100 on fleaBay for $100. Just carbon brushes and copper fields. The L3800 must have gold fields and ... ? platinum? brushes? WOW!

Guess you're quoting the Kubota price -- I have no idea what the Kubota price for mine is; my health is too fragile to risk asking!

D2Cat · Sep 6, 2015

ShaunBlake, why not take it to your local rebuilder? At least get an estimate. Just let him know it's from a 45 year old little mower and you're not spending much on it. Make him feel sorry for you!!

ShaunBlake · Sep 7, 2015

Cat man, that is a great suggestion.

I already have it stripped down and mostly cleaned up so I'll have a go at refurbishing it myself. It looks like the only parts I'll need are brushes and possibly a solenoid actuator. The bushings seem tight and if the fields are okay, I think I'm good to go.

Thanks!

Stubbyie · Sep 8, 2015

Don't put it back together dry.

Add a smear of good nonconductive grease like white lithium motor rebuilder grease to all the shafts, pins, bushings, bearings, and anything else NONELECTRICAL and work it manually before reassembly.

I had a starter on an old Ford 300 straight 6 get so dry after 40-yrs it wouldn't turn over when the bendix engaged. Took it apart and greased it up good and she's ready for for another 40-yrs or until I lose interest.

Please post back your continuing experiences so we may all learn.

BackYardWrench · Sep 8, 2015

ShaunBlake

I was messing with my starter over the weekend and could not get solenoid to push starter gear out UNTIL I connected a negative to the small spade connector on the solenoid. I also connected ground jumper cable to the body of the starter. With these connections, I go the starter solenoid to activate but could not get the starter to spin.

100 td · Sep 9, 2015

Clamp the motor and connect negative jumper lead to case. Get positive jumper lead and go directly to main motor wire, which shold be connected to solenoid. Motor should spin. If it doesn't spin, then you have a break in either the field circuit, the armature circuit or the brush connections. Your solenoid will not pull-in by itself normally, unless your motor works and has a complete circuit through it.

ShaunBlake · Sep 9, 2015

100 td;154863... Your solenoid will not pull-in by itself normally said:
Hmm... I din' know that. In that case, my approach is bass-ackwards: to rebuild the solenoid first.

So, this seems counter-intuitive to me. How does the solenoid know? Doesn't the solenoid do it's magic whether the starter isn't even there?

ShaunBlake · Sep 9, 2015

BackYardWrench said:
ShaunBlake

I was messing with my starter over the weekend and could not get solenoid to push starter gear out UNTIL I connected a negative to the small spade connector on the solenoid. I also connected ground jumper cable to the body of the starter. With these connections, I go the starter solenoid to activate but could not get the starter to spin.

John

Thanks, John; I've been jumping to it from the +. I'll give that a shot.

100 td · Sep 9, 2015

ShaunBlake said:
Hmm... I din' know that. In that case, my approach is bass-ackwards: to rebuild the solenoid first.

So, this seems counter-intuitive to me. How does the solenoid know? Doesn't the solenoid do it's magic whether the starter isn't even there?

Previously mentioned in post #2 & post #7, the solenoid circuit is completed through the motor circuit.
Perhaps these guys may be able to test/fix it
Gwinnett Auto Electric
5378 Buford Highway, Norcross, GA 30071-2602.

ShaunBlake · Sep 9, 2015

100 td said:
Previously mentioned in post #2 & post #7, the solenoid circuit is completed through the motor circuit.
Perhaps these guys may be able to test/fix it
Gwinnett Auto Electric
5378 Buford Highway, Norcross, GA 30071-2602.

I appreciate the reference to your previous posts -- I missed the meaning of a critical point in #2:

100 td said:
...
There is no circuit to the pull-in coil thru the brushes and armature. So when you belt the starter with a hammer and it starts, you have made the brush make contact with the armature and the pull-in coil now works and engages the starter.

And I don't recall seeing #7, so I've been going at it "bass-ackwards".

I appreciate the reference to Gwinnett Auto Electric. Tonight I took another look at the starter, noting the parts that need replacing (brushes, and one spring is broken, another is badly rusted) and weighing the difficulty of tracking down such things vs. getting an alternator/starter shop to do the deed. Time to get some quotes.

Again thanks, and I really appreciate your thorough and detailed comments. The 2x4 suggestion was priceless.

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