K1500 starter issues

[Erik the Awful]

The starter was spinning, but the engine didn't turn over. I pulled the starter, put it on the bench, and applied power directly from my jump box. It spins, but the gear never kicks out into the extension housing. I bench checked the new starter before installation and it performed as it should.

Are you going to tell me that's not a 'proper' bench check? I've diagnosed, repaired, and tested many '71 series Detroit Diesel starters on the top of a workbench. At over a grand per, you don't just toss them when they act up. I mean, you can, but I try to be a good steward of your tax dollars.

 

[Schurkey]

I installed hundreds of starters on 6V-92 engines. Never had one apart. Most of them were compressed-air powered. Maybe 1/3 of what we installed were electric. I can't speak with authority about bigass Diesel starters.

As for the "10MT" series of automotive starters, the starter motor gets power from the solenoid via a big copper disc that connects the copper battery cable post contact to the heavy contact for the starter motor power. The MOTOR is different/smaller/planetary gear drive on the "Mini-starters", but the solenoid and shift-fork, and the starter drive work the same.

The copper disc is spring-loaded AWAY from those contacts.
Photo 1. Solenoid cap, with copper battery cable lug (and brass "R" terminal contact) attached.
http://hbassociates.us/SolenoidCapContactsSM.jpg

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Photo 2. Copper disc with spring pushing it away from copper lugs mounted to solenoid cap. Starter motor contact, and "S" terminal contact attached to wires of solenoid. Cap can't be removed without disconnecting these lugs from the cap.
http://hbassociates.us/SolenoidContactsSM.jpg

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The only way the copper disc is forced into contact with the copper lugs in the solenoid, is when the solenoid plunger is pulled-in by the windings of the solenoid. The magnetism of the windings draws the solenoid plunger forward, the plunger hits the copper disc, moving it along with the plunger to the most-forward position. And that's how and when the starter motor gets electric current that powers it.

No plunger retraction, no power to the motor. No power to the motor, it doesn't spin.

If the plunger does retract, the shift fork that's attached to the other end of the plunger moves the starter drive into position--meshing with the engine ring-gear. The starter drive is meshed with the ring gear BEFORE the solenoid travels far enough to smack the copper disc into contact with the copper lugs. If it wasn't, the starter drive gear would grind on the ring-gear teeth.

So unless there's severe wear on the shift fork, I don't see how the starter motor can spin and NOT yank the starter drive into mesh. And if there was that severe wear, you'd be hearing grinding as the starter almost meshed with the ring gear.

I'm baffled as to how your starter can spin and NOT pop the drive out. Broken spring holding the copper disc away from the contacts in the cap??? Starter tilted enough on-the-bench that the disc flopped forward??? If that happened in-the-car, the starter would spin even if the key wasn't turned. Your starter would run randomly every time you hit a bump, or stopped suddenly. Doesn't make sense to me.

EVERY time I work on a starter that spins, but doesn't crank the engine--it's a failed starter drive one-way clutch that's slipping. The drive IS engaged/meshed with the flywheel, but no power transmits through the slipping one-way clutch. Starter motor sounds like a siren, engine doesn't crank. And in the early stages, the engine will crank sometimes, but occasionally it doesn't. It seems random at first. The more-worn the starter drive gets, the more-often it slips.

 

[Erik the Awful]

This afternoon I'll get some video. I was going to shoot a bit yesterday, but my jump box was dead. It absolutely spins but doesn't throw out the gear. It may be that the bendix on the gear reduction starters doesn't also close the contacts, but I'll also tear into it and see. To be honest, I haven't ever tried rebuilding a SBC starter. They're too cheap to bother.

 

[Erik the Awful]

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I was unsuccessful tearing the bendix apart. The whole starter is cheap garbage, but they used grade 8 torx screws to hold the solenoid on? More to follow.

 

[HotWheelsBurban]

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I was unsuccessful tearing the bendix apart. The whole starter is cheap garbage, but they used grade 8 torx screws to hold the solenoid on? More to follow.

If you do take it apart, be sure you mark the solenoid bolts. They only line up properly one way.....had the starter apart several times on the Burbs (that's how I learned).

 

[Erik the Awful]

Doh! I gotta man up and admit I was in a hurry when I shot the video and pulled a dumb move. I didn't even realize it until this afternoon when I finished work and kicked back on the couch for a ten minute nap. I let my brain rest a minute and it hit me. @Schurkey, I know I was defensive, and I owe you an apology. Sorry for that.

In the video, when I applied power, I put it to the output side of the solenoid, not the always-hot terminal. I was bypassing the solenoid. This afternoon I got some torx bits to tear the solenoid off for inspection, but before I pulled it apart I reconnected the jump box correctly and the stupid gear kicked out.

Now, I know why I removed this starter from the truck. It was only a couple weeks old, and the starter was whining without turning the engine over, and so I assumed the bendix wasn't kicking the gear out, but if it was a mechanical failure, why does it work now?

 

[thinger2]

"Doesn't engage the flywheel"

You mean, you turn the key, and the starter winds up and sounds like a siren? Other times it cranks normally?

Failed starter drive. It IS engaging the flywheel, (because the motor doesn't get power until the solenoid pushes the starter drive into position) but the one-way clutch in the starter drive is slipping, so the motor spins without cranking the engine.

Common as dirt. New starter drives are available, but most folks just replace the starter. By the time you remove the starter, tear it apart, replace the drive, replace the shift fork, replace the bushings and brushes...you might as well just buy a replacement starter that has a warranty.

Heat-related problems generally involve the starter motor turning slowly, or not at all. If it spins up like it's being bench-tested...it's the drive.

All of the above except. If you have a stock GM nose cone that works without any shims.
Keep it.
The orientation between the starter and the flywheel on a chevy is determined by the nose on the starter and the mount on the block and how all of that relates to the bellhousing casting on the transmission.
Tolerence stacking
A Ford bolts the starter to the bell and elimnates a lotta that "stack"
If you buy a new starter, you are only after the motor itself.
Swap the nose cone put new bushings in it and you dont have to do any of the shim bullshit.
A junior high school kid can do it.
My ex girlfriend can do it.
The kit is 25 bucks from NAPA.
This is all real easy to do you dont need a scanner or some wizard.
Its cake easy to do.