A minor setback, or an indicator of a bigger problem?

[1976GMC]

We are getting our GMC ready for an upcoming trip. After changing oil and successfully starting it few times I moved it out to be loaded. I the next start up, the starter made a single clunk and the engine would not turn over... Pulled the starter and discovered shattered starter gears. The flywheel looks completely intact. The starter gear looks like it's made via powder sintering method. I'm wondering if that's a contributor to the failure or if I might be looking at a bigger problem? I appreciate hearing back from people who know this better than I do.

 

[RoadTrippin]

I'd probably pull the plugs and get on that crank bolt and verify that you can turn the engine over. If so, plugs back in and put a new starter on it.

 

[1976GMC]

I'd probably pull the plugs and get on that crank bolt and verify that you can turn the engine over. If so, plugs back in and put a new starter on it.

Yep. Did that. When the old starter was still in, I could not turn the crank shaft by hand. Got extremely worried that I may have a hydrolocked cylinder from some kind of fluid leak. Pulled the plugs - no fluids in any of the cylinders. Still couldn't turn the crankshaft by hand. That's when I decided to pull the starter. Fou d btoken gear teeth... I installed another starter that I had laying round and the engine started right up and runs smoothly.

 

[LQQKatJon]

Yep. Did that. When the old starter was still in, I could not turn the crank shaft by hand. Got extremely worried that I may have a hydrolocked cylinder from some kind of fluid leak. Pulled the plugs - no fluids in any of the cylinders. Still couldn't turn the crankshaft by hand. That's when I decided to pull the starter. Fou d btoken gear teeth... I installed another starter that I had laying round and the engine started right up and runs smoothly.

That is unusual. Un-nerving, but I would call that failure a fluke and somehow you had a defective or bad gear. .

 

[Richard RV]

Yep. Did that. When the old starter was still in, I could not turn the crank shaft by hand. Got extremely worried that I may have a hydrolocked cylinder from some kind of fluid leak. Pulled the plugs - no fluids in any of the cylinders. Still couldn't turn the crankshaft by hand. That's when I decided to pull the starter. Fou d btoken gear teeth... I installed another starter that I had laying round and the engine started right up and runs smoothly.

 

[1976GMC]

That is unusual. Un-nerving, but I would call that failure a fluke and somehow you had a defective or bad gear. .

I hope you're right. I guess time will tell

 

[mech0001]

Yep. Did that. When the old starter was still in, I could not turn the crank shaft by hand. Got extremely worried that I may have a hydrolocked cylinder from some kind of fluid leak. Pulled the plugs - no fluids in any of the cylinders. Still couldn't turn the crankshaft by hand. That's when I decided to pull the starter. Fou d btoken gear teeth... I installed another starter that I had laying round and the engine started right up and runs smoothly.

"Back in the day" this sort of thing would happen with high compression engines that would kickback while starting and break the gear. Can't think of one that I ever saw like that. Timing too advanced might do it with a 455 though.

 

[pvfjr]

"Back in the day" this sort of thing would happen with high compression engines that would kickback while starting and break the gear. Can't think of one that I ever saw like that. Timing too advanced might do it with a 455 though.

I was troubleshooting a late 90's Vortec 350 that made horrible noises when trying to start. Sounded like it was violently kicking back. I thought that was odd, since everything was computer controlled. So I started some research.

I found a TSB that described this condition when the crank sensor starts going bad. Erratic timing (as much as 60 degrees of advance according to the TSB) was the cause, blamed on bad signals from the crank sensor. The TSB also advised that it could break the starter, or the engine block where it is mounted.

It couldn't hurt to look at the timing just to be safe. Make sure weight bushings and springs aren't terribly worn, chain isn't sloppy, reluctor signal is clean on o-scope, wire connections are good, etc.

 

[1976GMC]

Good points on the kickback. Now that I "replay" the scene in my head, it did sound like a momentary backfire happened as soon as starter began to turn. I will make sure to check the timin.