Bench testing starter, does this sound right?

rholmes69 · Jul 20, 2015

'03 2810, no symptoms of a failing starter, it just one day wouldn't crank. Made a 1/8 of a turn when the key engaged, then all lights flashed, needled bounced and when keyed off, it buzzed. Replaced battery, same symptoms. Checked the ground, cleaned, still good. Keying ignition would cause it to turn maybe one full revolution, then act like it jammed up on the compression stroke. Release key, try again, would maybe budge an inch; release try again and then it would turn maybe full revolution, repeat, etc, etc. I yanked the starter, pulled it apart, looks like brushes and armature visibly ok. Good contact on the carbon to the rotor, bearing and planetary gears spinning freely. When connecting directly on the bench, the starter turns, but it almost seems like it is slowly ramping up (initial speed is well over 100 rpm, it isn't spinning super slow, it just isn't hauling butt like I would think it would. I am used to them wanting to just torque themselves out from under your foot. This one is cranks up and it seems like the longer I leave connected to the battery, the faster it will start to turn. I have to remove the positive lead because it starts glowing pretty red and looking like it is going to "weld itself" onto the positive lug. Bendix operates normally

So cliff notes question, should the starter crank pretty hard when it fires up, like it would twist its way out of your hand or from under your foot? Is it normal for the starter to "ramp up" to speed?

Fawken · Jul 20, 2015

Sounds like shorted windings.

BigRol · Jul 20, 2015

Did you check the bushings to make sure the armature isn't touching the fields?

rholmes69 · Jul 20, 2015

I couldn't see any that it was touching the fields, although when I first pulled went to pull it apart, I couldn't spin the core by hand, so I guess it might have been... I have never rebuilt a starter before and really have limited experience messing with them... I use to help in a car parts shop and I remember bench testing starts back in the day, that is really the only experience I have with them. But I am a very mechanical person and have done everything except to completely rebuild a motor, so sometimes I am a little fearless when tearing into things when maybe I shouldn't

... stupid tax my wife calls it...

Fawken · Jul 20, 2015

How does the starter smell? When I troubleshoot electric motors the smell sense is my #1 tool.

rholmes69 · Jul 20, 2015

Oh man, I don't know how it smells. I don't smell anything "burnt"....

burzynsr · Jul 20, 2015

A DC motor (starter) should produce all of its torque immediatly. If it is ramping up to full speed something is defenitly wrong. If the terminal is glowing red that also indicates extremely high amperage draw. Is it worth fixing? Just wondering how much and how far out for delivery is a new unit?

BigRol · Jul 20, 2015

If you have a part # and make I can get the particulars for you, if its touching(poling)you should see the marks on either end of the armature, some times a simple bushing is all it takes. can you check to see if the nose piece fits snug on the drive end and same with the backplate on the ce commutator end.

SPYDERLK · Jul 20, 2015

rholmes69 said:
'03 2810, no symptoms of a failing starter, it just one day wouldn't crank. Made a 1/8 of a turn when the key engaged, then all lights flashed, needled bounced and when keyed off, it buzzed. Replaced battery, same symptoms. Checked the ground, cleaned, still good. Keying ignition would cause it to turn maybe one full revolution, then act like it jammed up on the compression stroke. Release key, try again, would maybe budge an inch; release try again and then it would turn maybe full revolution, repeat, etc, etc. I yanked the starter, pulled it apart, looks like brushes and armature visibly ok. Good contact on the carbon to the rotor, bearing and planetary gears spinning freely. When connecting directly on the bench, the starter turns, but it almost seems like it is slowly ramping up (initial speed is well over 100 rpm, it isn't spinning super slow, it just isn't hauling butt like I would think it would. I am used to them wanting to just torque themselves out from under your foot. This one is cranks up and it seems like the longer I leave connected to the battery, the faster it will start to turn. I have to remove the positive lead because it starts glowing pretty red and looking like it is going to "weld itself" onto the positive lug. Bendix operates normally

So cliff notes question, should the starter crank pretty hard when it fires up, like it would twist its way out of your hand or from under your foot? Is it normal for the starter to "ramp up" to speed?

Thats exactly how it should act. Check the bearing/bushings. The armature is probably dragging.