Won't Start When Hot

[Don]

Boy, do I ever need some good advice...I have a BC12D 1946, with a C85. I fly somewhere , land, shut down on a warm day. After a half hour or 45min, the engine just won,t start...I hand prop for 20minand not even a pop...Sometimes I don,t prime, still no run. Some times I prime and still no run. When I prop , I don't hear the squish of gas, just a hiss of air. Does this mean I have a vapor lock, or is it flooded? There isn't any gas running out of the cowling.... I have to let it sit for an hour or so, and then prime till gas runs out, then pull the prop backwards with the throttle wide open, then close the throttle, and prop about 20 times and sometimes it will start , otherwise I have to let it sit till the engine cools to ambient temp.....There has to be a better way......Any suggestions will be gratefully be accepted...Don

[d.grimm]

Re: Won't Start When Hot

Check your coils in your magneto's. They break down under heat. Don't ask how long it took me to figure that out.
Dave

[Pearson]

Re: Won't Start When Hot

If you have an actual primer, maybe it is letting air leak by.

If you are just pulling the prop through, maybe you aren't priming enough.
Try pulling the prop through enough so that you see fuel dripping.

Check the easy stuff first.

[Goneflyin]

Re: Won't Start When Hot

I've found with my 65 if I leave the throttle open while parked after shutting down it starts much quicker (CLOSE THE THROTTLE!) after short stops. Someone told me with the heat under the cowl the gas in the carb boils and goes up the intake tract. They're all different but it works on mine.

Bill

[Mark Julicher]

Re: Won't Start When Hot

Coils causing weak or zero spark when hot. 90% chance that is your problem. Borrow a good magneto or have yours tested.

[flyguy]

Re: Won't Start When Hot

That is a pretty common compaint for a hot -85. While it may be mag problems, I expect you would also notice the problem with a long climb on a hot day if it were. It isn't likely to kill both of them at the same time either.
Likely the carb is just boiling or at least vaporizing a lot.

Couple of tricks: Never turn the engine over under those circumstances with the ignition off, you'll really flood it if you do. Just position the prop, turn on the mag. CRACK the throttle (that will give you more than one bang to keep it moving so it doesn't flood, and leans the mixture, really) and just pull it through.
When that doesn't work, turn off the mags, TIE THE AIRPLANE DOWN, open the throttle and turn the engine over BACKWARDS. Yes Mildred, regardless of what the "ole pros" tell us, backwards works fine, it is just a pump.
Try starting it as above again. Don't forget to set the throttle a little off idle for the above mentioned reasons.
Repeat all of the above as necessary.
Darryl

[M Towsley]

Re: Won't Start When Hot

Darryl,

Though I have covered this before, try opening the throttle as you shut down. Be brisk while doing it. There are shutdown procedures for these small Continentals. I had the same problem you did. When you shut off the mags the prop is still spinning and pulling fuel into your carb. That's the squishing sound you hear. I remember feeling as though my arms were going to fall off. It was just flooded. Do not reprime or you are right back to where you started. Remember to return the throttle to idle after everything has stopped. Barely crack the throttle when you are ready to go again. Do not prop it with the throttle closed or you reprime it again. Also check the primer, if it was not locked down you can be pulling fuel in. You can search the old threads regarding this. I know searching can be a pain but there is a wealth of information on this site and after awhile some folks don't want to retype the answers to the same question over and over. Good luck and I hope this helps.

[Howard Wilson]

Re: Won't Start When Hot

Another 'trick' that's worked for me is to let the engine low idle for about a minute before shut down and shut it off with the fuel not the mag switch....?

[1938BF50]

Re: Won't Start When Hot

Howard,

When you do this, do you then reprime for a hot start?

[flylo]

Re: Won't Start When Hot

What works for me is letting it run at 1000 RPM & shutting off the fuel making sure to shut off the mag switch after it quits. Then to restart turn on the mags & start it. Don't prime, don't rotate the prop, just start it. Works great for me. Each plane has it own little procedure you have to learn.

[Howard Wilson]

Re: Won't Start When Hot

Howard,

When you do this, do you then reprime for a hot start?

Nope, try it first without prime, if it hits once or twice but doesn't start give it one shot. etc.

[flyguy]

Re: Won't Start When Hot

Yes, ad that to the list. Shut down the engine by turning the fuel off with it running at high idle, 1000 sounds about right. Just doing that would probably eliminate the problem most of the time.
DC

[NY86]

Re: Won't Start When Hot

Don:

I think there's some benefit to figuring out what the root cause is. Next time it happens, pull the top plugs out and see if they're gas soaked. If they're not, see if there is spark. If there's spark and the plugs are not flooded, then it must need more fuel (unlikely...)

It's nearly impossible for a gravity feed system to vapor lock unless the fuel line is wrapped around the exhaust stack.

[Arnold Wallace]

Re: Won't Start When Hot

I've always found it starts on the first pull when the tail is tied down.....Murphy's Law.

[flyguy]

Re: Won't Start When Hot

Does anyone in the south 48 use prime in the summer time? I think I used about a 1/4 shot 2 times, in the summer, since I got this plane. Wouldn't consider even a small shot of prime with a hot engine.

I just pull mine thru 4-6 times with the trottle closed all the way for a rich initial mixture. Crack throttle and pull thru (not flip) one blade. 99.9 percent effective. The old girl has some other problems that fortunately don't effect her flying, but she is really good about starting.

Every once in a while something will get under the steel needle valve and I will get a dripping carb. Always goes away.
DC