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Hot Start Tips

Navion EGROUPS Compilation on Hot Start Tips

My Navion (with G0-435 and pressure carburator) starts great when it's cold but it's more difficult when it's hot (i.e., trying to start it when it's been running within the last hour or two). Any hot start tips?
Paula Tomlinson
N422HJ

For 10 years mine started perfect. its down for rebuild now. When its hot I never gave it any thing, just one quick 4 seconds of the fuel pump, left it off turn the key to left mag, one half inch of throttle, pushed the start button. The mag timing needs to be set correctly of course. I found when it was hot that to much fuel didn't work. Note: I should have said full rich also.
N5198K 1950 B GO435 pressure carb.
Mike Galbreth

I have the IO470C and it does not hot start well either. What I do is full rich, throttle 1/3 to 1/2 and start cranking. While it is turning over I turn on the fuel pump to high and when the engine catches I wait about 2 seconds and then turn off the fuel pump. It over revs but at least it starts.
Terry Bradshaw

The best way to hot start, is to turn the fuel pump on, the ignition on, and hit the start button. do not Prime. 90 % of the time it works, if it does not -----it instantly floods and you have to clear it as follows. turn ignition off, mixture lean, throttle wide open, and turn it over 3-4 times, then ignition and pump on , rich mixture, and hit the start button
David Fretwell

Yes, hot starts are a problem for the Navion. The worst scenario seems to be when you make a fuel stop. That's just the right length of time to let the fuel lines soak up a lot of heat while there's no air flowing through the cowling. Here's what I do in that case: After I land, park and cut the engine, I open up both sides of the cowl. This allows the engine heat to rise and dissipate freely, instead of cooking the fuel lines and causing vapor lock. After ten minutes or so, the engine is cool to the touch and can closed up again.
Bob Coiro

I have a similar, perhaps the same, carburetor in my GO-480 Navion B, and hot starting is a problem for me, too. I use a little bit of everyone's approach, I guess. When I land, I open the cowls to cool things off. If it's too windy to leave the doors open, I pop the oil door and that does help. On startup, if the cylinders are too hot to touch, I do not prime, run the electric pump for fifteen seconds or so, crack the throttle, and go. If the heads are warm but not hot, I use standard start procedures: pump, prime (two shots), three twists of the throttle and start. But if all else fails, the one sure means of starting (assuming you have a battery left) is FULL THROTTLE, MIXTURE IDLE CUTOFF, one hand on the start key and the other on the throttle. It may take a few turns, but the correct mixture for combustion WILL be found and you will have a start. Note that I have also installed two batteries in my Navion, so there's always plenty of power.
Robin White
N5329K

I found that purging the fuel lines by pulling the mixture to cutoff, opening the throttle and running the electric fuel pump for about 15 seconds cures the problem. As it was explained to me, the pump pressurizes the carburettor but at mixture cutoff the fuel bypasses back to the tank via the vapor return line. After purging I just use full rich, 1/4 inch of throttle and hit the starter.
Gary Plewa
N91719

I'm not a GO-435 expert, but will offer a couple of tips.....
1) A hot engine will vaporize fuel in the fuel lines and pump, and in order to get it started hot, we need to get cooler fuel into the pump, so it will pump fuel, not vapor. You can pull the mixture to IDLE-CUTOFF, and run the boost pump for 30 seconds (a long time, but it should flush out the vapor, and fill the pump with liquid fuel).
2) A hot engine needs MORE AIR to start than a cold engine....so, push the throttle IN about a half inch MORE that for a cold start.
I use the boost pump ON to start a hot engine, and leave it ON till running smoothly. With the advanced throttle setting, be ready to retard the throttle as soon as you get a start!
Good luck,
Jimmy Boyd

Thanks for all the tips, can't wait to try them out!
Paula Tomlinson
N422HJ