Rotax 377 won't start

[j_omega]

I recently purchased an small ultralight with a Rotax 377. The previous owner hasn't started it in several years. Needless to say, it doesn't want to start now. I have replaced the fuel filter, fuel line, and plugs. It ran for about 5 seconds one time and occasionally, you can hear it "pop" once. Apart from this, the engine is not doing anything.

Right now, the procedure is full choke and no throttle.

What should I look at next?

4169

[Frank Giger]

Air, spark, fuel.

I'd clean the carb, as when an engine just sits, that's where most of the varnishing and crud accumulation does it's work.

[Greg Wilson]

Air, spark, fuel.

I'd clean the carb, as when an engine just sits, that's where most of the varnishing and crud accumulation does it's work.
Agreed, also be certain that the fuel pump is working, new pulse line, and that the diaphragms are not stuck from old fuel or perforated. I had an engine in which the congealed oil in the pump just "glued it all together.

[Frank Giger]

I was swapping an Army story with a buddy of mine about the days of the Jeep and the time his conked out in much the same way - it died and then started briefly and then wouldn't re-start. We did a lot of stuff that was outside of the approved user maintenance level, to be sure, suspecting the whole time it was the fuel pump.

Heck, when we pulled the fuel line from the carb and cranked it, nothing was coming forth.

And then John had the great idea of trying it again from the pump side of the fuel filter, which looked fine to us. Sucker was a plug, not a filter. We knocked a bunch of crud out of it and managed to get enough flow to get us back to the motor pool.

So I'd start there, with filters.

[j_omega]

Update: I cleaned the carb today and the engine started up fine.

[Greg Wilson]

Good to hear. You may want to try and use non-ethanol fuel if you can, when sitting the alcohol will absorb water from the air and make real nasty goo. I used avgas for my last bit of pre-mix before storage (when all the local car gas had ethanol in it) before storing for the winter. To store it fog the engine as well and tape off the exhaust and air intakes, (tape a bag over the air filter) and drain the carb. I'm thinking storage here now, 36*F this morning in northern MI, winter is closing fast on me. Again glad to know you got it running, have fun with it.