need help...backfire and fuel shutoff valve not working

[katanajer]

hi guys,

so my DA20-A1 continues to backfire after shutdown from a long flight.

the other problem i have is i tried to shut it down by closing the fuel valve, but my engine keeps running and not shutting down. fuel seems to continue to be go in with no signs of the engine trying to quit.

any help would be great.

[Antoine]

Jerry I am afraid you need a mechanic to take a hard look. It is unrealistic to do this kind of diagnostics with no access to the faulty engine.
It is a Rotax 912 in the A1 I think and I would not hold my breath as there are not too many Rotax gurus on this forum anyway.
Don't let the engine continue backfiring on you - you may be doing expensive (and potentially dangerous) damage. I would take it to a competent Rotax person right away. An aircraft engine should run with no hiccups at all or (I) would stay on the ground.

[rwtucker]

Jerry -- Did you (a) make sure that your plugs are free of lead & carbon deposits and (b) check your timing? Do you follow a shut down procedure to minimize plug deposits and starve the engine of fuel before shutting off the mags? Do you aggressively lean when taxiing, and lean for at least 1,350 EGT when in the air?

[krellis]

The A1 with the Rotax engine autoleans, so it cannot be starved of fuel via the mixture control (there isn't one) so it cannot be leaned in the conventional sense. If your engine is not shutting off with the key (the normal method) you either have a bad ignition switch (check the service bulletins for the ACS switch issues) and/or you have a CDI ignition box with an open ground wire. We had this issue once before when we rented the A1 we now own. One of the wires had come out of the terminal crimp.

Your backfire issues may be related, but I'm guessing you have some throttle cable issue and/or an idle speed setting that is too high on one or both carbs.

The engine should eventually shutoff with the fuel shutoff valve, but it takes a little while. If it does not shutoff after a couple of minutes, do not fly again until you have all these issues resolved. Clearly there is something going on with your plane.

Krea Ellis
DA-20-A1 N853DF
DA-40 XLS SOLD