Cold Weather, Remember how to Start Engine

A guy showed me a trick for cold starting the C172SP IO-360: after running the fuel pump (mixture rich), wait 60-120 seconds for the fuel to vaporize in the cylinder, then attempt starting (mixture cutoff until she fires, usually 2-3 blades). Worked well for me when I was working as a CFI.
 
How big is your fire extinguisher? :mad3:

To be serious, no I haven’t. That would be a lot of ether that’s in the long and wide intake tube leading to the carb box. A backfire at this time would be a fuel air “boom”. The idea gives me great pause. Interested in hearing others.
 
AV8R_87 said:
I wonder what their reasoning was. That air is usually less than 120F, and it uniformly warms up the engine. I don't see any issues with doing that to an engine for an hour or two in cold weather, warming everything up.
If anything, I wonder if their concern is not warming the engine enough, leading to uneven temperatures. I recall some people were against oil pan heaters because it did nothing for the cylinders.
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I have a vague recollection of someone explaining to me that with continentals the moisture evaporated out of the oil would condense further up in the engine and cause corrosion problems. Hopefully posting this will get someone to confirm or deny.
 
AV8R_87 said:
I wonder what their reasoning was. That air is usually less than 120F, and it uniformly warms up the engine. I don't see any issues with doing that to an engine for an hour or two in cold weather, warming everything up.
If anything, I wonder if their concern is not warming the engine enough, leading to uneven temperatures. I recall some people were against oil pan heaters because it did nothing for the cylinders.
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As I recall, it was a concern about uneven heating.
 
Gilbert Buettner said:
When I owned a V-tail Bonanza, the engine operating instructions specifically advised against this way of pre-heating. I used an oil pan pad heater and a big quilt or moving blanket over the cowl. Always the night before flying in northern Minnesota, Wisconsin and lower Michigan. I often flew when OAT was below zero F.
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AV8R_87 said:
I wonder what their reasoning was. That air is usually less than 120F, and it uniformly warms up the engine. I don't see any issues with doing that to an engine for an hour or two in cold weather, warming everything up.
If anything, I wonder if their concern is not warming the engine enough, leading to uneven temperatures. I recall some people were against oil pan heaters because it did nothing for the cylinders.
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On my Mooney I have 2 Revlon hair dryiers. Low is about 800 watts. I put one in each cowl flap and a blanket over the cowl to heat both sides evenly. I preheat if below 30°F. I also own a battery operated propane forced air heater. I thought I could use it if away from home, but it is not as reliable.
 
If you are cold starting a carburerated engine with a working fuel priming pump this method will start it every time. Set carb open about 1/4 throttle, or just crack open about twice as far as you normally would on a warmer day. Pull the primer out and be ready to pump. Begin cranking and after the first blade passes the windscreen begin pumping vigorously until it starts, then stop pumping. Be ready to pump again in 2-3 seconds if the engine stalls. Adjust throttle and pump again as needed to keep engine running at low speed until pumping is no longer needed. Lock down the primer and let the engine warm up at low speed.

This works because you are moving the AF ratio from a too lean to fire condition to a rich enough to fire condition. If it is cold outside and the engine is cold it will likely go lean and stall again 2 seconds or so after starting. Pump again as it spins down just enough to keep it running. As the heat builds the gas will evaporate better and engine will run OK on its own. This method worked every time on my old Cherokee O-320 Lycoming.
 
it’s unlikely the two hair dryers can adequately warm the oil in an hour or two in sub 10° temperatures, which is what Lycoming uses as their preheat threshold.
 
WDD said:
Us tie down, hangar challenged folks without electricity just have to make do with propane.
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Actually someone here pointed out the jackery line of portable batteries…just plug in your tanis to the jackery and 30 minutes later you can go!

Of course that works once unless you have a solar panel or a regular outlet to recharge from
 
Pinecone said:
And they were against LOP operations. :D
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I don't agree that Lycoming excludes LOP operations. Service instruction 1094D states:
"For a given power setting, best economy mixture provides the most miles per gallon. Slowly lean the mixture until engine operation becomes rough or until engine power rapidly diminishes as noted by an undesirable decrease in airspeed. When either condition occurs, enrich the mixture sufficiently to
obtain an evenly firing engine or to regain most of the lost airspeed or engine RPM. Some engine power and airspeed must be sacrificed to gain a best economy mixture setting."

That sounds like LOP operations to me.
 
William Pete Hodges said:
If you are cold starting a carburerated engine with a working fuel priming pump this method will start it every time. Set carb open about 1/4 throttle, or just crack open about twice as far as you normally would on a warmer day. Pull the primer out and be ready to pump. Begin cranking and after the first blade passes the windscreen begin pumping vigorously until it starts, then stop pumping. Be ready to pump again in 2-3 seconds if the engine stalls. Adjust throttle and pump again as needed to keep engine running at low speed until pumping is no longer needed. Lock down the primer and let the engine warm up at low speed.
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Carbureted engines will be a lot easier to start if they have a few new primer nozzles.

1735173180767.png


This little thing is what sprays the fuel into the intake manifold. It's more than just a fitting with a tiny hole in the business end. Behind that little round plate that's staked into the end of the fitting are some tiny machined channels that take the fuel via tiny holes from the fuel inlet, and those channels are at a tangent to the center hole. The fuel is made to spin at a high rate so that when it exits it forms a conical, fine spray that vaporizes well and fires off promptly.

These fittings have residual fuel in them after priming, and when those nozzles are in the cylinder head they get real hot and the fuel in them cokes them up and they won't work right anymore. They'll just dribble the fuel, and that dribbling fuel is large droplets that just end up running down the intake port walls instead of being sucked into the cylinder in a rich vapor that will ignite nicely. I have tried to clean them but it's pretty much impossible. The passages are so tiny. I even built a pressure canister with threaded ports to screw these into, with strong carb cleaner/carbon dissolver in the canister under pressure to force it through to clean the nozzles. Didn't work. I spent more money (time) fooling with that than the cost of several new nozzles.

The larger Continentals used two 90° nozzles, one in the aft end of each intake runner, AN4023-1:

1735173794742.png


They last a lot longer because they're far from the heads and don't get so hot.

I had one customer whose airplane (a 180) was hard to start. I found that someone had replaced plugged primer nozzles with these AN fittings, which are straight through and don't atomize anything:

1735174040990.png


I put in two new AN4023-1 nozzles, reinstalled the proper tube end fittings, and boy did that O-470 fire up instantly.
 
I was previously priming my engine, yelling "clear", and then waiting a few seconds before engine start. Worked okay, but the engine sometimes took a bit to get going. Then I read /heard somewhere (I want to say it was a Mike Busch book or podcast) that pushing the primer in *while* turning the starter (instead of before) is more effective. I tried it (two priming strokes and the third once the starter is engaged), and holy cow it's a much more immediate start. Has definitely helped on some cold mornings!
 
Randomskylane said:
Actually someone here pointed out the jackery line of portable batteries…just plug in your tanis to the jackery and 30 minutes later you can go!

Of course that works once unless you have a solar panel or a regular outlet to recharge from
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I have a chevy Volt. It has a 14kWh battery & its own generator. The 360Vdc to 12Vdc converter can handle 1,200 watts continuous. I've hard wired in a 2 gauge extension with a connector and an inverter with the same connector. If I take the time, I can hook up my Reiff heaters, battery charger, and a small heater under my instrument panel while I preflight or clean up the plane.
Works well.
 

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William Pete Hodges said:
If you are cold starting a carburerated engine with a working fuel priming pump this method will start it every time. Set carb open about 1/4 throttle, or just crack open about twice as far as you normally would on a warmer day. Pull the primer out and be ready to pump. Begin cranking and after the first blade passes the windscreen begin pumping vigorously until it starts, then stop pumping. Be ready to pump again in 2-3 seconds if the engine stalls. Adjust throttle and pump again as needed to keep engine running at low speed until pumping is no longer needed. Lock down the primer and let the engine warm up at low speed.

This works because you are moving the AF ratio from a too lean to fire condition to a rich enough to fire condition. If it is cold outside and the engine is cold it will likely go lean and stall again 2 seconds or so after starting. Pump again as it spins down just enough to keep it running. As the heat builds the gas will evaporate better and engine will run OK on its own. This method worked every time on my old Cherokee O-320 Lycoming.
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Have you done this?

My experience with Lycoming primers is there is no "pumping vigorously" possible.
 
William Pete Hodges said:
I don't agree that Lycoming excludes LOP operations. Service instruction 1094D states:
"For a given power setting, best economy mixture provides the most miles per gallon. Slowly lean the mixture until engine operation becomes rough or until engine power rapidly diminishes as noted by an undesirable decrease in airspeed. When either condition occurs, enrich the mixture sufficiently to
obtain an evenly firing engine or to regain most of the lost airspeed or engine RPM. Some engine power and airspeed must be sacrificed to gain a best economy mixture setting."

That sounds like LOP operations to me.
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May or may not be. Could be one cylinder too lean and the rest still rich.

Also the turbo instructions are for clearly Peak (Economy) or ROP (best power).
 
Also remember campers that it gets cold inside the instrument cluster as well.

One fine crisp morning my AI was stuck to one side; plenty of vacuum, DG working. I weaved back and forth on the ramp to get the AI to swing left, back to right, etc, until it finally it behaved.
 
WDD said:
Also remember campers that it gets cold inside the instrument cluster as well.

One fine crisp morning my AI was stuck to one side; plenty of vacuum, DG working. I weaved back and forth on the ramp to get the AI to swing left, back to right, etc, until it finally it behaved.
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I would put a 100-watt trouble light on top of the rudder pedals to keep the gyros warm.
 
AV8R_87 said:
I wonder what their reasoning was. That air is usually less than 120F, and it uniformly warms up the engine. I don't see any issues with doing that to an engine for an hour or two in cold weather, warming everything up.
If anything, I wonder if their concern is not warming the engine enough, leading to uneven temperatures. I recall some people were against oil pan heaters because it did nothing for the cylinders.
Click to expand...
Probably that it's really good at warming up the outside of the engine, and not so good at warming up the parts (and oil) that really need it.
 
Pinecone said:
Have you done this?

My experience with Lycoming primers is there is no "pumping vigorously" possible.
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You have to use it regularly or it will freeze up. When I first bought my Cherokee it wouldn't work at all. I got it freed up with penetrating oil and started using it every first start. Same thing with the carb heat. It was inop too and took a bit to free it up. I made sure to use it on every landing.
 
Stewartb said:
Winter flying in Alaska has taught me a lot about cold weather engine management and I’ve tried pretty much every preheater imaginable, and have created many of my own. Away from power, preheat requires a combustion source. A flame to heat an engine requires attending the flame. Not much fun with -30° and a breeze blowing. That minimizes preheat time to just enough to get the engine started. All the talk about made-up temperature thresholds is amusing to me. I’ve started Coninentals and Lycomings in single digits when I needed to. I’ve frosted plugs, too, and that’s a mission killer so I learned how to avoid it. Preheating below 20° per Continental instructions has worked fine for my engines, including Lycomings. Flying in those temps requires other prep so it’s not a burden until it gets cold enough to hurt. For that? I’ve evolved to 1000w generators and Reiff heaters.

Cold engines 101. Oil pan heaters thin oil and make starters spin better. Faster spinning helps cold cylinders fire more reliably but cold cylinders scuff. Air cooled cylinders are difficult to warm with a sump heater. Cylinder heaters make fuel distribution better and combustion easier, but starting with gooey oil isn’t good for the engine. A combination of both is the best solution. Hot air heaters are almost never used long enough to warm the oil and are probably the worst idea for engine health, especially propane heaters that pump water vapor into the cold engine compartment. Preheating the oil takes hours, not minutes, and quick development of oil pressure is the benchmark you need to shoot for.

In 20°-ish temps? I prime, pull the prop through several rotations, prime a little more, then start. Learn to minimize how many blades go by before the engine fires. Do some hand-propping in winter and you’ll figure it out quickly. Cold engines require more prime. Cold temps require more fuel in flight, too. Make sure your carb provides a minimum of 150° of leaning authority in the temps you fly in. Cover your oil cooler as required to achieve adequate oil temps. Don’t worry about cold CHTs, those are rarely a problem even in sub-zero. Learn what cold temps do to your prop efficiency and limit takeoff rpms if warranted. Dress like you’ll have to walk home.

Winter temps improve airplane performance. Have fun!
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Good post. One of the advantages to living with my airplane now is I can drag it outside and experiment with starting at different temperatures after cold soaking. I learned that my IO-360 powered cub will not start at 5F without engine preheat. Lycoming recommends preheat below 10F of course, but theoritically 15W oil (aeroshell 15W-50) should perform adequately down to -4F (-20C), at least when the oil is new/fresh. That is the temperature at which the oil is tested in the cold crank simulator to perform sufficiently, and it's rated even lower -13F (-25C) for adequate fuel pump flow (mini rotary viscometer test). I believe the failure to start is a combination of cranking resistance due to the thickened oil and degraded battery performance fom my EarthX ETX-900TSO at cold temps.

I was using a 6-7 second prime followed by 30 seconds of waiting then 10 second cranking/1 minute rest technique. Every 3rd 10 second start attempt I would reprime for 2-3 seconds. It was too much prime juding by the fuel dropping from the cowl after the experiment. After 6 tries I gave up. The voltage drops substantially during cold starts below 20F, from the 13V to 6-7V range during 10 second cranking attempts. Next time I will try for a 10F cold start with a jump pack and see if that gives the battery what it needs to crank the engine well enough. Then I can experiment with cabin heat (battery is under seat) and the reiff engine preheat as well as the emergency camp-stove derived multi-fuel preheat contraption I carry around in winter.
 
172andyou said:
I have a vague recollection of someone explaining to me that with continentals the moisture evaporated out of the oil would condense further up in the engine and cause corrosion problems. Hopefully posting this will get someone to confirm or deny.
Click to expand...
That is a concern if you leave the sump heater on all the time because the moisture never gets a way out of the engine (or not for very long times). If you are going to go fly and you use it to warm the oil, then subsequently go fly and get the engine warm, it will blow the moisture out. I use a combo sump heater and 100w light bulb for my bonanza (overnight) when I'm flying in the Idaho winter and it's nice and toasty when I get there but I don't turn them on unless I plan to fly.
 
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