Rebuilt engine starter behaving oddly
 

My first post but I have loved the forum as I have worked on the old XJ. Super helpful as I haven’t worked on an engine for a long time but have now run into a problem that I haven’t seen before. I rebuilt the 4.0 on the 93 XJ and the starter is behaving oddly. It seems to catch and turn the engine once then slips then catches in regular pattern. I got a new starter thinking that was the issue but it is still the same. I have attached a video. Any ideas?

So it did this with your old starter too? Did it do the before the rebuild as well? Did you have the engine or transmission out during the rebuild? Did you remove the flexplate?

Yes, I did a full rebuild of the engine and had the trans rebuilt at the same time. I figured at 200k miles or so it was probably a good idea while it was out of commission anyway. The flywheel looked fine when I put it back in, no missing or chipped teeth that I could see.

It made this noise with the old starter so I pulled it and checked and it looked okay but I really couldn’t come up with anything else so got a new one and it is doing exactly the same. Oh, but it did not do this before the rebuild.

Did the ring gear wear appear as though the starter drive teeth were fully engaging?

It looked really good before the rebuild. No obvious wear at all. I didn’t notice any wear when I swapped out the starter after the rebuild but I probably had tried to start it 10 times so it wasn’t a lot of time to wear down.

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So it is doing the exact same thing with the new starter as it did with the old, so we can rule out a bad starter armature. I am almost inclined to say that your flexplate might be slightly warped, as it is catching and releasing at the exact same interval/spot.

You have what is called a flexplate. Flywheels are for manual transmissions, Flexplates are for automatics.

Could be. Easy to check. Remove starter and put a pointer or dial indicator by the flex plate. Rotate the engine by breaker bar and observe. It won't run completely 'true' but shouldn't be too far off either. Is there much crankshaft end-play?

I'm inclined to check the depth of the starter nose/bendix. How far in does the starter drive go? I would also check the armature commutator bars. I've had them come off (literally fall off) on starters in the past. You can pop the starter apart and check it out. Or just get a different starter. They're not that much.

Given I have already swapped out the starter I am inclined to think it might be warped as well. I was hoping someone might have a fix that is easy to fix! Thanks for the thoughts, I will check the flex plate (I know that is what it is called but when I was young I always worked on manual cars so just tend to refer it as a flywheel) and see how it looks.

Check the run-out before jumping to conclusions. The way 'rebuilt' starters are made these days it could still be a crappy starter.

Listening to the audio on your video, it sure seems like it is the "turning" side that is disengaging instead of the "getting turned" side. Typically you will get a grinding/skipping sound with a bad flex plate. It sounds more like the starter motor stops engaging while it is still turning (and then somehow reengages). Do you have a remote starter switch so you can watch what the starter is doing under there?

All good suggestions. I'd take the inspection plate off and have someone crank it to see if it actually stops turning when it makes the noise.

That is a good idea. I don’t have one but will look to find something. I agree on the sound but it would be really remarkable for an old starter and a new replacement to have exactly the same “on off” intervals. Any ideas what might cause that other than something weird in the starter itself?

Well, finally got the inspection plate off and the flex plate appears to be turning fine and not warped or cracked. Still making the weird noise. I don’t think the not starting is related to the noise but am not sure. I am going to check the timing and everything else for that but am still really curious about the noise.

Also, on a separate note, anyone know what this connector is supposed to go to? I can’t find the other end.x

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Has the engine started and ran since you rebuilt it?