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912iS engine won't crank

I fly an RV-12iS. Yesterday, the engine would not crank when the starter was engaged. No noise, no clicks, no change in amps or volts, nothing. There are no faults, both Lanes A+B on and illuminated. Tried shutting down electrical several times, but no luck. So I got out, and rotated the propeller maybe a quarter turn, got back inside, and it started just fine. Taxied to fuel and started no problem. Any thoughts?

The engine has just over 600 hours, no other problems. Went out today and again it wouldn't start until I rotated the propeller a quarter turn.
I don't see how rotating the prop would make any difference, based on the electrical schematics..

So I think, for now, its coincidental. At these high hours, I'd suspect something is intermittently grounding out.. though I suppose its possible a pin has finally backed out just far enough.. There's a lot going on with the starter.. knowing whether voltage is actually getting to the relay when turning the key would eliminate a lot of items to check.. But I'll try to make a list of things to check:

0. Faulty starter relay. Moving part, prone to failure. Even if it is activating, would you hear the click/clunk from inside the cockpit? Easy enough to test, but difficult if the problem has been intermittent.

0a. Ground to the engine, or wire from relay to starter isn't secure.

1. Faulty pin/wire to the ignition module. Check that the large d-sub connector is secure and that pins 8, 12, 13, 20, 25 haven't backed out of the connector.

2. At the HIC module's large d-sub connector, verify pins 3 4 7 12 13 haven't backed out, loose, etc.

2a. Possibly a problem with the 8-pin HIC module connector, if you haven't already performed the Service Bulletin on that. The original connector is known for making intermittent connections. If you haven't done SB-00058 already.. stop here and do it now.

3. Faulty relay on the ignition module board (doubtful, since the Spar Pin warning light would be ON). While you're able to reproduce the problem, holding down the Spar Pin Override button while turning the key (and it still not working), would eliminate this relay as a possibility.

4. Check the new HIC module's LED light while the starter isn't working. Note the color.
On some designs the starter motor can get a "hot" spot and if it stops in the same spot it has a carbon build up and and wont energize. Move it to clear that spot and away you go. My old Beetle would do it once in a while. Put it in gear and push it slightly, Bobs your Uncle!
zap! I think mcmark is on the right track.. I'm pretty sure this starter's teeth are always engaged with the crank/engine.. so rotating it would jostle the starter a bit.. maybe make it start working.

I've heard of the oil seal on the starter failing too.. allowing oil into the starter and messing up the innards.. so.. this might be the start of something that'll be getting worse...
I'm pretty sure this starter's teeth are always engaged with the crank/engine.

9-Series Rotax do not have "teeth" on starter motor. A one-way clutch (Sprag Clutch) is used as a over-running device so starter motor is not back-driven by the engine....