912S Hot Starting issues

[N82HB]

You all have helped all of my issues so far, so here I go again.

I have flown quite a few 912S powered airplanes and I have never seen this so I want to know what I need to change.

My Kitfox starts just fantastic when it is cold or if it has been sitting for 15 minutes. But when I come in and shut down and try to light it off again in less than 5 minutes it seems to be flooded. I have to open the throttle a bunch and spin it quite a few times to get it started.

Do I need to change my shut down procedure, my starting procedure, or the engine set up? Anybody had similar issues?

Thanks again,
Kelly

[catz631]

Kelly,
It kind of sounds like "vapor lock" to me at first glance. What kind of OAT are we talking about? Are you closing the throttle below 2000 rpm and letting the engine cool for a bit before shut down ? Also the procedure I use is to reduce the throttle to about 1400 rpm(after cool down) then one mag off,wait about 1- 2 sec then the other mag off. This has worked well for me
Dick

[Av8r3400]

Fuel return line is the real answer...

Kits are available from LEAF, CPS, Lockwood and probably directly from the McBeans.

[N82HB]

I will try all of the above; Thanks a lot!
Kelly

[catz631]

I don't have a fuel return line on my engine and have never had a problem but then I have the 80 hp . The fuel return line might be the answer.
Dick

[Dave S]

Hi Kelly,

I had a transient issue with this - I had some 92 octane auto gas that had been purchased in the cold weather then put it in the plane when it was 92 degrees - normally I have not so much of a hot start problem but this time it was embarrassing - it is my understanding that refiners formulate auto gas to a different vapor pressure in the cold weather compared to the during the hot weather.

No idea if this is part of you experience or not as the problem you have observed can have many causes or combinations of causes.

I did find out that flipping the oil door open on shutdown mitigated the hot soak issue a bit - gave a hole for the hot air under the cowl to leave through. (yes, for the record - I closed it for restart!)

I have been thinking about the return line thing a bit too - just haven't done it. Also thinking that the bare naked steel fuel filter under the cowl makes a pretty good spot for under cowl heat to migrate to the fuel.

Sincerely,

Dave S
KF7 Trigear