G

gciampa

Active Member
Hey folks,

Over the past few weeks, with the temperatures dipping into the 20's overnight, I've been searching for best practices on starting my O-360 with the morning temperatures below freezing. The new and improved technique, is the following:

1. Mixture rich
2. Throttle 1/4 to 1/2 inch
3. Fuel pump on to normal fuel pressure then off

Warm Weather Steps:
4. Throttle push forward two or three times to squirt some fuel and back to 1/4 inch.
5. Mash the start button

New and Improved Cold Weather Steps:
4: Throttle push forward two or three times to squirt some fuel and back to FULLY CLOSED.
5. Mash the start button and pump the throttle with quick motion between FULLY CLOSED and 1/4 inch.

Engine starts in just a few compression strokes, amazing.

A colleague of mine gave me this technique, the idea being that modulating the carburetor butterfly valve between fully closed and slightly open, creates just enough turbulent airflow to vaporize the cold fuel.

I had searched Lycoming reprints, VAF, SACRANCH and the "interweb" thing w/out finding any help. The best I could find was verbiage saying the critical factor was getting the right fuel/air ratio, duh....

Works for me anyway...two days in a row...temps around 25 at night, 28-30 in the morning...

NOTES:
* I do not have an engine prime lever
* Without the rapid throttle motion on start, it would take three, five to eight second starter cranks to get the engine started on a cold morning
* Warm weather starting is always on the first or second compression stroke
 
I rarely, if ever give advice - I simply state what I know....but in this case, I would advise strongly against pumping the throttle without the engine cranking! This will dump fuel into a puddle in the air box, and if you have a backfire, an engine fire can easily result. I always pump the throttle to prime, but ONLY when the engine is cranking - the suction created draws the fuel into the cylinders and gives you a nice start.

Please consider this a safety warning - I have seen airplanes catch fire during start because of pooled fuel.

Paul
 
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I agree 100% with Paul. Do not pump the throttle unless the engine is turning, to avoid the risk of fire. The accelerator pump shoots a stream of fuel into the venturi when rapid throttle movements are made. With a carb on the bench the accelerator pump will shoot the stream 15 feet into the air.

With the above said, I've been using this technique to start carbureted engines for years, and its been 10+ years since I've used a primer on any carbureted airplane I've flown.
 
O-360 carb engine here. Based upon comments here, I only pump the throttle when the prop is turning. Don't care if it is the first actual revolution or the first or second after pumping the throttle.

Removed the primer several years ago when the feed line broke.
 
Lycoming does not recommend accelerator pump startings . I found with the cold weather a delay between priming and start works better. My procedure is to prime as I enter aircraft, do the seat belts, headset etc then start. One blade is all it needs. Its the vaporized fuel that starts the engine and with cold weather it takes a little longer to vaporize.
Happy New Year, starting it out right with a flight.
 
If you do this at anything less than 20 degrees you are a fire waiting to happen. A guy in the flying club did it on a 172 and burned a lot of the FWF. Watched another guy burn the right nacelle up on an Apache. You could see the stream of burning fuel every time he pumped the throttle. If you have a primer system it is much safer to get a shot prime ready and as you crank the engine use the primer to start it then push in the mixture. Also if you are starting your engine without pre heat at under 30F it is not good at all.
 
Just a semi-educated guess, but I think that the manufacturers are reluctant to recommend throttle-pump priming because folks do it when they aren't cranking, and t seems to be hard to educate folks on how to do it. Without question, if you are not comfortable with it, don't do it - and DEFINITELY don't pump when you aren't cranking.

Nothing wrong with a dedicated primer ... if you've got one...

Paul
 
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Ironflight said:
Nothing wrong with a dedicated primer ... if you've got one...
Click to expand...

Glad you mentioned that. There is No way, that I'd get rid of my primer system. I figured that if this thread lead to, too many........remove or don't install primer systems......that I'd butt in. We like them around here. Temps are ranging from 7-15 F. today.

L.Adamson --- RV6A
 
L.Adamson said:
Glad you mentioned that. There is No way, that I'd get rid of my primer system. I figured that if this thread lead to, too many........remove or don't install primer systems......that I'd butt in. We like them around here. Temps are ranging from 7-15 F. today.

L.Adamson --- RV6A
Click to expand...

What are your cold start procedures with the primer? How long do you prime, and do you pump the throttle while cranking a time or two or just hold it closed since you've already primed?

Thx.
 
sjarrell said:
What are your cold start procedures with the primer? How long do you prime, and do you pump the throttle while cranking a time or two or just hold it closed since you've already primed?
Click to expand...

Throttle just opened the 1/4" or so. Fuel pump on, prime on for 3 seconds approx. No pumping at all, and no cranking until I release the primer switch. My primer system is from Van's, and splits to three cylinders.

L.Adamson --- RV6A
 
L.Adamson said:
Throttle just opened the 1/4" or so. Fuel pump on, prime on for 3 seconds approx. No pumping at all, and no cranking until I release the primer switch. My primer system is from Van's, and splits to three cylinders.

L.Adamson --- RV6A
Click to expand...

I have the same technique with my primer system and the engine usually fires with a blade or two. I'm only priming two cylinders so it doesn't take much
 
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