Thread: car wont crank
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Old 01-13-2010, 12:04 AM
long-gone long-gone is offline
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Join Date: Jul 2009
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The chain guide rails are just that, guides. While they keep the chain from roaming and slapping around somewhat, they mostly provide a steady, even, lubricated and regulated path, especially as the rpm increases. On your headless motor, there will be a guide rail exposed on the right, which is a two-piece plastic (nylon?) channel. On the left side, the top of the chain tensioner rail is exposed. This I believe is aluminum with a plastic/nylon guide cast over it. You can definitely crack a guide rail, particularly an old brittle one. I guess you could crack or chip the plastic on a tensioner rail as well. While it's probably critical when the motor is running it's hard for me to see that a damaged/cracked guide could jam a motor and keep it from merely cranking or even idling.

On the other hand, if either were damaged/cracked, and the motor was cranking and consequently broke off a piece of plastic, depending how big it is I suppose it maybe could get caught in the crank gear or something. I think it's kind of unlikely it could jam things up. Starters are extremely strong and I'd think it would just chew a piece of plastic up. But I can't say it's impossible.
Causing it to skip a tooth might be more likely but even that seems a little tough to reckon. Even if it skipped a tooth the motor would still turn. If you skipped enough teeth, I don't know how many but the pistons would contact an opening valve and yes, the motor definitely would jam.

To have removed the head, you would've needed to turn the crank to set the timing marks. Where are those tools now? (27mm socket and a ratchet)

Perhaps that's the problem, the mechanical timing was incorrectly set, or not properly marked/maintained while working on it, and now it's locked up. If this is the case, you need to stop trying to use the starter before you bend more valves or damage a piston.

You must check it by hand before you proceed. If you find you can't budge it clockwise, try backing it up, but just a small amount - like a quarter turn or less. If it does back up gently turn it clockwise again, if it feels like it's hitting something and stopping you might have some disassembly to do.
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