Dave
The spark plug connectors simply unscrew from the plug wire. On My 914 the
spark plug wires have a stranded wire in the center, so if you are going to use
the same plug wire, just cut off about 1/8 th or a quarter inch then reinstall
the plug boot.
Jim Brown
N398JB
David DeFord wrote:
>
> On my way to the Copperstate fly-in on Friday, I stopped in Bishop to pick
> up Kevin Klinefelter. We heard a loud, irregular popping noise in our
> headphones while taxiing to the runway, and the runup showed one rather
> rough mag. We checked the plugs and wires, finding no obvious problem with
> the wires, but the four plugs in the front cylinders were all very black,
> though they had only a few hours on them. (The rear plugs were all fine.)
> All plugs were replaced, and everything seemed smooth, including a standard
> runup. (During the troubleshooting, the engine had gone from very hot to
> very cool, with the cowls removed.) The popping noise began again on
> takeoff, so we returned to Bishop, and I dropped off Kevin. With poor
> weather in the forecast for the next day, I headed for home (180nm across
> the 13000-foot peaks of the Sierra). After a couple of episodes of very
> loud popping during the climb, everything quieted down again, so I continued
> on up to 15500 feet (912S/Airmaster power), crossed the mountains, and made
> it home without further incident.
>
> There are four ignition coils on the 912/914 engines, with each coil firing
> two cylinders (one live, one with valves open) at once. I measured the
> resistance between the pair of plug wires from each coil, and found 17K
> between the top plugs, and open circuits between the bottom plug pairs. The
> suspect coil (based on the rough mag and the black plugs in the front
> cylinders) is the forward coil on the port side, which fires the bottom
> front plugs. It is nearly impossible to see anything in the tangle of wires
> and hoses in this area, so I tried to remove the coil. After much struggle,
> I got most of the way to the coil, but determined that it would be necessary
> to either remove the engine from the ring mount, or remove the starboard
> side intake manifold to get the coil out. Access to many parts of the
> engine is difficult, but this is ridiculous.
>
> Each plug wire is sheathed in a rubber sleeve, which covers the "tower"
> where the wire enters the spark coil. Two of these sleeves are broken at
> the coil end. Does anyone know how to remove the spark plug connectors from
> the wires, or the wires from the coils? At least one of these must be
> necessary, in order to get the wires through the sleeves, and also through
> various other sleeves and holes. I suspect that the connectors may unscrew,
> but I'd hate to damage one by trying the wrong thing. The coils come with
> wires attached (at $280 each), but the wires and sleeves are also listed as
> separate parts. It seems likely that my problem is a wire that is sparking
> to the engine, or possibly sparking across a break in the coductor, but I
> can't figure out how to remove them for further testing or replacement.
>
> If anyone has experience troubleshooting or repairing the Rotax ignition
> coil assemblies, I'd certainly appreciate any advice.
>
> Dave DeFord
> N135TD
>
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