New starter's pinion gear doesn't engage flywheel - Huh?


#1

The starter in my '93 Dakota was dying (usual signs of worn brushes) so I replaced it with a new one from AutoZone. The starters looked the same, and after calling back to double check the part #, the store swears it’s the right part. However, when I engage the starter, it spins but the pinion gear doesn’t engage the flywheel. I can’t see how I could have installed it wrong - the two bolts seem to have only one place they can go. Any ideas what’s wrong?


#2

made in china?


#3

You could bench test the new starter and see if the bendix is really pushing the gear out all the way. Could be a bad bendix.


#4

Dunno - good question. It’s a ‘Duralast’. What’s ‘Duralast’ in Chinese …?

More seriously, if the starter motor spins up, is a manufacturing error likely to keep the pinion gear from engaging?


#5

Take it back to Autozone. They probably have a test fixture to test it right in the store.

I purchased a non-oem starter motor ($75) for my Corolla from a chain auto parts store a year or so ago. It didn’t work straight out of the box. It was a pain, not so much that it was defective, that sometimes happens with any part, but that I had to install it, then remove it. Wasted a lot of time. I just took it back and got my money back. Then I took my old starter motor to an auto-electric shop where they fixed it. For $10. Still working fine.


#6

Yosemite - good point. I’m hoping for something not involving removing the dam thing - maybe some kind of adjustment. Because it’s a 4x4, you gotta remove the left rear tire while standing on your head to get the starter out. (Ok, not quite, but almost.) If I don’t find a better solution I’ll pull it and test it.


#7

Also, sometimes starter motors need to be shimmed to properly engaged the flywheel gears. I’ve never had to deal with that, but on some engines apparently it is commonly needed.


#8

I had one from napa, binding and sounding horrible I pulled it to take it back, and thought I ought to take a video, so re installed it, making sure all was aligned correctly and have not had a problem since. There was talk about shims etc., luckily I did not have ro go there. The other possibility is you have broken teeth on the flywheel. In the olden days we would move the flywheel by pushing down on the fan belt turning and forcing the fan to move the flywheel, doubtfully an option now.


#9

George - great suggestion - I’m pretty sure it just needs new brushes. If it wind up taking the new one out I’ll try getting the one I have fixed.


#10

On Toyota’s the usual failure mode is the starter solenoid contacts corrode/wear away, rather than the brushes. But either way, it won’t work. And both are easily fixed at your local auto-electric shop.

edit: There’s another advantage of just fixing the existing one. The gears have worn to exactly match the flywheel teeth.


#11

Try to rotate the drive gear in each direction, it should turn (freewheel) in only one direction. If you can turn it in both directions the one way clutch is defective.

You can watch the drive gear extend with the starter on the ground by using jumper cables. Be careful, there is alot of torque, get a firm grip.

Are there signs of damage/conntact on the ring gear (flywheel)?


#12

Thanks Nevada - If I pull the new one to test it I’ll check that. It’s hard to see much but I didn’t see any obvious signs of wear on the flywheel teeth.


#13

If you do the experiment Nevada suggests, you can also check if the pinion pokes out the same distance as the old one. Make sure there are no gasoline vapors around. I did it and there is a lot of sparking involved.

I’ve found buying auto parts an interesting experience. And not necessarily in a good way. When I first went in to buy that starter motor, the staff guy came out with one that didn’t have the correct number of teeth on the pinion gear. And the mounting holes were of the wrong sex. You know, one sex is where the bolt goes through a smooth hole in the starter motor, and screws into the block. The other is where the bolt goes through a smooth hole in the block, and screws into the starter motor.


#14

It’s always best to have the original starter rebuilt, if at all possible. That way you know it’ll bolt right in and work. The one from Autozone sounds defective.


#15

Remove the starter and press on the bendix gear in both directions. It should be free to turn in one direction but difficult to turn in the other because it will drag the armature with it. If it can be turned in both directions the Bendix is bad.

Did you compare the original starter to the one you bought? If not call Auto Zone and ask them to hold your old one so you can closely compare them. Parts stores have problems with customers mixing parts up on the counter and getting in the wrong box. There are different starters for different transmissions and engines.


#16

Since the solenoid needs to be functional to close the contacts that enable the motor circuit, and the same mechanical parts that enable the starter motor circuitry also extend the starter gear, I’d suspect an improper installation or, as Barky suggested, busted flywheel gear teeth. You would not be the first person to change a starter motor only to find out the ring gear on the flywheel had some teeth missing.

Try looking at the ring gear teeth with the starter removed. You’ll likely need a lighted inspection mirror, but that’s a worthwhile purchase anyway. Let us know what you find.


#17

This is a problem that should be able to be determined on a benchtop.

As to rebuilt products, and even new, a certain percentage will turn out to be problematic.
Assembly line rebuilding of automotive products is often done with the same care used in snapping together children’s plastic toys. Most pass muster; some don’t.


#18

Mountainbike - My first thought was improper installation, too, but I can’t see what I could have done wrong. It seems pretty fool proof - Just tighten on the two bolts - nothing to adjust. Is there some subtlety to the installation I could’ve gotten wrong?


#19

That there thing the gear is attached to could break in the old days. Maybe the new days aren’t much different. Try installing the old one on it.


#20

@bcompton‌

I believe your starter was originally made by Denso

That means it probably has the same problem as George’s starter . . . the contacts

I don’t know what engine you have, but Rockauto.com lists the contacts for your car.

Perhaps it’s worth it to remove it, take it apart on the bench, clean everything, and replace those contacts

I’m sure you could bench test it pretty easily yourself

And if it doesn’t work, just get a quality rebuilt part, or have it rebuilt, like George said