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When mine failed as long as the engine started, the ring gear apparently stayed in place and didn't make any noise. This was on a racecar, so high rpm. After thinking about it some more, mine made kind of a zinging noise when trying to start. I think the ring gear was kind of spinning in place, slightly askew, but still on the flywheel. I can imagine the ring gear in some position though that would generate some rock grinding noises. The mechanic that repaired the ring gear was able to push it back into place through the starter hole and tack welded it in place. I raced it that way for several more years. I found a picture I took of the flywheel before I recycled it a few years ago.
A month ago I had a pinion bearing fail on my diff fail about 30 minutes before the end of 14 hours of racing. It sounded like a bucket of bolts and the rearend would lock up intermittently. When I checked it later, I expected to find all kinds of metal chunks. Turned out there was nothing (including oil, which is why the failure) floating around. The noise was primarily the pinion backing into the LSD housing (see pic). I only bring this up to note that weird noises can have totally unexpected causes.
Anyway. I will be interested to hear about it all was.
New starter from Atkins. First turn of the key…. Crunching noise, followed by much cursing from myself. Second turn of the key…. Lovely clean noise of the engine turning over. Tried it again a few more times and all sounds grrrrrrrrreat! Except for the grrrrrr bit.
Here is a mystery and possible clue. Pic of new starter, and old one taken apart. Gears are totally different in length, diameter and tooth count. And starter had defn been off before as the female mounting hole was helicoiled.
Fixed for now. If it comes back, I paint marked the gear ring and flywheel so if noise comes back I can see if the gear ring is slipping around the flywheel.
Housing over the gear is different too. Who knows if it even matters? Car ran great for the last year with the old one installed. And now it starts with the new one in place. Ah well.
You post reminds me that I believe I have saw two different pinions listed (with different numbers of teeth) for Rx-7's. The 8 tooth (like your old one) is the one you normally see. I would assume the one with more teeth would spin the flywheel slightly faster but have less torque.
So you have your old starter apart? Are there any signs of damage or wear inside it that would explain the grinding noise?
I did indeed take the old one apart to see if I could find damage. But nothing obvious. Only thing I can think of is the freewheel device that allows the shaft to spin freely when the engine fires may be failing internally. Like a bicycle freewheel when it starts to fail and the chain jumps forward under load. Could not get it apart though so inconclusive.
Am a little concerned as have tested maybe 20 turns of the key and twice I got a crunching noise. Let go of key, turned it again and started right up. Going to remove the starter again and see if the paint mark across the ring gear and flywheel still lines up. That will tell me if ring gear is sliding around the flywheel.
The starter teeth are interesting. The picture below shows the stock starter (top) that was in my car for a long time. It appears to have smaller no. of teeth. It started having issues so I made a Frankenstarter using the higher power (2kw) motor from an FC auto tranny starter and the nose from an FC manual tranny starter, because the auto tranny nose wouldn't work with the FB. That one has the higher no. of teeth. Can't remember if I noticed the difference in the pinion gears :-o Anyway it worked and has been going strong since beginning of 2019. Kind of weird
My fingers are crossed that your problem is solved.
I've never owned an FB or FC and am not intimately familiar with some of their parts. Manual and auto SA starters are quite a bit different from each other. While the manual starters (SA vs. FB) look similar, the auto ones appear quite a bit different. Both have the higher output motors but the SA auto looks to be unique to itself. The nose is much smaller. SA auto (top) and manual (bottom)
Logic, common sense and the evidence before me says the existing starter with the smaller diameter / smaller tooth count pinion had started to skate over the tips of the teeth of the ring gear, catching on some and glancing off others. This could produce the horrible crunching rock grinding noise I heard, and also cause the engine itself to stutter forward spasmodically as the teeth caught and skipped.
The new starter has a larger diameter pinion, with more teeth and which are longer. Theory is this pinion is engaging deeper into the ring gear and starting fine.
The occasional, more familiar crunch that I heard with the new starter every few key turns has now gone. It was the much more familiar zzzzzzsup sound heard when the pinion does not push into the ring gear, not the slower deeper scarier non rhythmic crunching I got with the old starter.
06-15-23, 12:35 PM
