rear engine after rain storm

[Kim Geyer]

Think your mag switch might be getting leaked on?

[rmorris]

if you are talking about the switch to turn on mags up front...no, I don't think so

also, if it was mags related - I think (and again, this is all conjecture) that it wouldn't start right up and run 5-10 seconds then shut off....Herb's thought it is fuel related was my first thought, so I went to extraordinary sumping after big rain events. my current theory that it is water drippng in top engine inlet onto top of air filter and saturating it (again, only after heavy rain event)...so it starts up, but then begins sucking all that water from air filter into engine...then it takes a bit before it clears out.
that's my working theory

when I say minutes of cranking, I literally mean many minutes (doing it in cycles to let the starter cool down)

I think I may try the following experiment:
- soak the plane through that top scoop at a washing bay, then see if the engine displays the problems.
- assuming it does (which reinforces my theory), then put some sort of cover over the scoop (yes I saw link for the $150 cover, but think I may be able to ddo something more along the lines of a camping style rain fly that is much more lightweight to carry around)
- the try to resoak and repeat test
my guess is that I will get to doing something like this in the next month or so

[skymstr02]

Other things to consider, check the grounding cable from the engine to the airframe and the power wire to the rear engine starter. Sometimes reinstalling these after an engine change gets missed.
You may not be getting a full 24v to the starter because of a weak contactor or corrosion in the starter wire, or the grounding cable may have a voltage drop due to poor connections.
If the engine is not spinning fast enough, the impulse couplings may not be engaging.
Check the resistance from the starter motor mounting stud to the rear cowling mount flange, and check the voltage to the cable stud on the starter motor. It shouldn't be a volt or two below battery voltage.