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No primer, cold weather start

My Continental O-200A doesn’t have a primer, and starting at cold morning temps has been quite a crap shoot, even straight out of (unheated) hangar.

Do you have a method that works reliably?

I heard the following from a fellow pilot:

  • Pump with throttle about 5 times
  • Exit plane, and turn prop by hand through a few blades AGAINST its usual rotation (not sure why, maybe to suck the ejected fuel into the cylinders?), and stop just before a compression step
  • Enter plane, pull carb heat, pump throttle 1-2 times and crank
  • If it starts up, pump throttle a little more

So quite the dance. Any opinions (other than “dude install primer”)?

LFHN, LSGP, LFHM

I don’t know where you get this AGAINST rotation from, but this has the potential to ruin your vacuum pump. Don’t.

Would it make sense to rotate against rather than in regular rotation if plane doesn’t have vacuum pump?

LFHN, LSGP, LFHM

Assuming your engine is cold,

To hand prime: close trottle, full mixture, open trottle each time the prop cranks a positive turn and the mags clicks, stop when you smell unburn fuel in the exhausts or at your lucky number, mine is 6

If you flood it, then purge fuel: poor mixture, open trottle, negative turns of the prop as much as necessary (basically untill you die)

I think you need two people to do it correctly, I don’t know what AGAINST means but for an easy start the prop has to stop on mags clicks (that is when max compression is suppose to happens?) but it does not have to if the hand/electric starting mechanism is strong, then if the prop turns normally you get fuel in if it turns opposite you get fuel out….

The aircraft on which I do this does not have vacum gyros nor alternators, so whatever you do with the prop has to do only with engine and fuel/oil, of course you can enjoy a free flying hour if you turn it 200K rotations backward and you are billed on tacho ;)

Last Edited by Ibra at 27 Feb 17:08
ESSEX, United Kingdom

I don’t have a primer. Two pumps of the throttle is enough from cold for my Lycoming O-320-B3B – you might want to experiment by reducing the amount of throttle pumping you do.

Andreas IOM

Would it make sense to rotate against rather than in regular rotation if plane doesn’t have vacuum pump?

The extent to which this is an issue is system dependent. Different vacuum pumps have different limitations. Some I have had are OK to run in reverse. I have also never heard of a pump ruined just by hand turning of the engine.

Administrator
Shoreham EGKA, United Kingdom

For the Continental O-200: pull through 3-4 blades (approximately) with fuel on, mags checked off and throttle fully closed. Then crack throttle 3 mm and start engine.

Later Continental carbs have an accelerator pump like a Lycoming which can prime the engine, earlier carbs do not. Try the method I’ve described and see how it works for you. If you end up needing additional prime from the accelerator pump (when applicable) make sure you still pull the engine through before starting. The helps the engine to start quicker and reduces the chance of backfire.

Peter wrote:

Different vacuum pumps have different limitations. Some I have had are OK to run in reverse.

That’s correct, however how many pilots (even owners) know if the one they have is good to run in reverse? It’s simply a risk not worth running.

Silvaire wrote:

For the Continental O-200: pull through 3-4 blades (approximately) with fuel on, mags checked off and throttle fully closed. Then crack throttle 3 mm and start engine.

For clarification, that means manually turning the prop about 1.5-2 full revolutions in its regular direction? Do I understand correctly that the intention is to circulate the oil and get fuel in the cylinders via the mechanic fuel pump?

And by “fuel on” you mean “electric fuel pump on” or just “fuel selector on”? (Sorry if this should be obvious.)

LFHN, LSGP, LFHM

Ibra wrote:

To hand prime: close trottle, full mixture, open trottle each time the prop cranks a positive turn and the mags clicks, stop when you smell unburn fuel in the exhausts or at your lucky number, mine is 6

Are you talking about full-on hand propping here, or merely priming the engine?

If I understand correctly, you describe turning the prop by hand, and when you come to a mag click (compression stroke), the guy in the cockpit opens the throttle. You pull the prop through the click, and the guy in the cockpit closes the throttle again? Mags and electric fuel pump are off during this procedure? Why can’t you leave the throttle (partially) open during the cranking?

LFHN, LSGP, LFHM
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