O-200 cold weather starting

[Bede]

I have a C150 with O-200 that has a difficult time starting in the cold weather (-25C). I think all O-200 are like this, but this is the only C150 that I have any time on. Even when plugged in (oil pan heater) + a buddy heater, the engine only starts with difficulty. The core temperature is around 15C (measured with thermometer gun). Following the cold start procedure, the engine usually fires, turns a few revolutions, then quits. Even starting the engine after a flight (still warm), the engine does this. This leads me to suspect that the extremely cold air has something to do with it. I have a similar problem with my lawn tractor (with snow blower). The only way to start in the winter is to put a heat gun to the air intake and blow hot air in.

I can get the O-200 started, by, once firing, put the throttle 1/2-3/4 of the way in allowing the RPM to immediately go to 1700 RPM and then backing off within a few seconds. I shouldn't have to do this IMO.

Any insight into what is causing this and any suggestions to solve? I think there is a service letter with a baffle that goes over the air filter limiting the amount of cold air.

Also, the engine is relatively new (~200 SMOH).

[digits_]

I'm not sure if it is part of the cessna cold start procedure for the 150, but does pulling the carbu heat help after it runs a bit? It seemed to help on our flying club airplanes many moons ago.

[2R]

The engine was originally designed to run on 80/87 . If you are using 100 ll it will be a richer mixture on start .
Baffles might restrict volume and not warm the air like the bicycle pump effect .
Adding to much fuel can actually cool the gas being generated in the ignition process . If you are using the accelerator pump to help prime it be very gentle with it as it can cool the combustion process . You only need to generate enough gas from combustion to pressure the cylinders to move , so the engine will breath more air for the gas generation to occur smoothly .
At very cold temperatures you might have too much fuel going in as the fuel is very dense . Back out the mixture an inch or what may work to lean it and see if that helps a lower rpm start .
For every gallon of gas you make almost a gallon of water . Hence you can frost the plugs and then your only hope is to use the accelerator pump to catch a spark and then hope the engine holds together during the start as some cold starts can be frightening if you are trying to keep the engine balanced . And you are paying the maintenance .
Do not forget a carbon monoxide detector in winter flying as the cabin heat from the 150 is heated over the exhaust, and if you do a couple of crazy starts you might crack the exhaust enough to give you some sleeping gas in flight . Battery operated Co2 are on sale at the hardware store

[l_reason]

I’m sure you are priming it a couple times before you try to start it. Airplanes don’t have a choke, just the primer to richen the mixture for the first few seconds. What works well on some of the small continentals is leaving the primer knob OUT. Once the engine has fired but starts to stall. Quickly push another shot of fuel in, it should come back to life. Pull the primer back out and get ready to push more fuel in if it tries to stall again.

Once it runs without the extra fuel from the primer you can ease the primer back in slowly, be sure to lock it in.

Good luck

[digits_]

I’m sure you are priming it a couple times before you try to start it. Airplanes don’t have a choke, just the primer to richen the mixture for the first few seconds. What works well on some of the small continentals is leaving the primer knob OUT. Once the engine has fired but starts to stall. Quickly push another shot of fuel in, it should come back to life. Pull the primer back out and get ready to push more fuel in if it tries to stall again.

Just be careful this doesn't happen: http://www.avcanada.ca/forums2/viewtopi ... 4&t=143951

[Aviatard]

The engine was originally designed to run on 80/87 . If you are using 100 ll it will be a richer mixture on start .

I'm having trouble wrapping my head around this. Assuming all else is the same, how does a higher octane fuel result in a richer mixture?

[AirFrame]

What works well on some of the small continentals is leaving the primer knob OUT. Once the engine has fired but starts to stall. Quickly push another shot of fuel in, it should come back to life. Pull the primer back out and get ready to push more fuel in if it tries to stall again.

Once it runs without the extra fuel from the primer you can ease the primer back in slowly, be sure to lock it in.

FWIW, this was SOP on the 7-cylinder Continental radial on my dad's Cessna 190 in colder weather, so it work on the larger continentals too. I'd seen it so regularly that when I was learning to fly and we got into the colder months, I did it one morning and my instructor freaked out at me... But the 150 started and kept running, while the plane next to us ran its battery down trying to get going.

[Big Pistons Forever]

I can get the O-200 started, by, once firing, put the throttle 1/2-3/4 of the way in allowing the RPM to immediately go to 1700 RPM and then backing off within a few seconds. I shouldn't have to do this IMO.

This is quite undesirable as running the engine significantly above idle right after start means the main bearings will not be getting full even oil pressure and so premature bearing wear is likely

I would suggest the problem is the engine may be warm but the fuel is cold soaked. Because it is cold it doesn't vaporize very well so the engine quits right after start up because it runs out of enough vaporized fuel air mixture to run. As other have said a shot of prime just as the engine dies will often get it over the hump, so have the primer out and loaded before cranking. Carb heat helps because it warms the incoming air which helps the fuel vaporize. Carb heat on right after start will immediately smooth out the initial engine roughness at idle on a cold day.

[Bede]

This is quite undesirable as running the engine significantly above idle right after start means the main bearings will not be getting full even oil pressure and so premature bearing wear is likely

Agreed. I've only had to do it a couple times. The POH does mention something about that. It's only for a couple seconds though.

I would suggest the problem is the engine may be warm but the fuel is cold soaked. Because it is cold it doesn't vaporize very well so the engine quits right after start up because it runs out of enough vaporized fuel air mixture to run.

I suspected something like this. Just not sure what to do about it. I have tried carb heat and the shot of primer trick.

[Big Pistons Forever]

This is quite undesirable as running the engine significantly above idle right after start means the main bearings will not be getting full even oil pressure and so premature bearing wear is likely

Agreed. I've only had to do it a couple times. The POH does mention something about that. It's only for a couple seconds though.

I would suggest the problem is the engine may be warm but the fuel is cold soaked. Because it is cold it doesn't vaporize very well so the engine quits right after start up because it runs out of enough vaporized fuel air mixture to run.

I suspected something like this. Just not sure what to do about it. I have tried carb heat and the shot of primer trick.

Another option is to load the cylinders before start. That is after priming pull the engine through 2 full turns ( make sure Mags are OFF ! but still treat the prop as live). Then add one full shot of prime and hit the starter. The idea is that there is enough fuel air mixture in the cylinders to get the engine to start and then the fuel in the last shot of prime will keep it running long enough to get it over the hump.

[2R]

The engine was originally designed to run on 80/87 . If you are using 100 ll it will be a richer mixture on start .

I'm having trouble wrapping my head around this. Assuming all else is the same, how does a higher octane fuel result in a richer mixture?

Me too after re-reading it

As both fuels have a very similar flash point and specific energy values , the main reasoning for the additional lead is lubrication and smother burns preventing knocking noises .
Just seems 80/87 has a bit more nose about it , so I assumed it would make more vapour . I have seen the putting out a cigarette trick in a bucket of 100 ll . Only works if you are quick , too slow and you will get your eyebrows burnt. At the fire hall they had fun with some fires . A bit too much fuel in a cylinder and you flood out the vapours and prevent vapour production so no ignition of the vapours to get the combustion stroke started . The problem in a cold start is the fuel is too cold to produce vapours . That is why some large radials used ether cartridges to aid starting . A small engine with some pre-heat should not require to drastic variations from a normal temperature range to wake it up from winter hibernation .

The use of the throttle accelerator pump should only be used if the engine is turning and can breath the fumes in or you risk a a fire .

[AirFrame]

Another option is to load the cylinders before start. That is after priming pull the engine through 2 full turns ( make sure Mags are OFF ! but still treat the prop as live). Then add one full shot of prime and hit the starter. The idea is that there is enough fuel air mixture in the cylinders to get the engine to start and then the fuel in the last shot of prime will keep it running long enough to get it over the hump.

I've been told pulling the prop through (forwards) will just push the mist out into the exhaust pipes, and lead to the possibility of a backfire.

Pulling the prop through backwards instead, pulls the mist into the intakes. When you later hit the starter, the prop turns forward, and sucks the extra fuel into the cylinder to burn, rather than igniting fuel in the exhaust pipe as it exits.

[PilotDAR]

Consider your vacuum pump as you consider turning your engine backward. I avoid turning engines backward...

[photofly]

Aren't vacuum pump vanes symmetrical? Why would turning them immensely slowly (compared to the usual rotational speed) backward be harmful?

[CpnCrunch]

POH says "with ignition switch off and throttle closed, prime the engine four to ten strokes as the propeller is being turned over by hand". Presumably that means forward.

[PilotDAR]

Most vacuum pump vanes are angled so as to "trail" the rotational axis. Okay when turning forward, as they will tend to lift themselves over debris or imperfections in the vacuum pump bore. When turned backward, the vanes can tend to bind into gunge in the bore of the vacuum pump. They, and the central housing for the vanes, are very brittle. If they break, or bind and shear the drive, a replacement vacuum pump will be required.

Another reason to preheat the engine, I've known moisture to freeze the vanes, and the first turn of the prop (either direction) can break them. In the mean time, forward is the way to go!

Photos in this atricle:

https://www.cessnaflyer.org/maintenance ... -pump.html

[AirFrame]

Consider your vacuum pump as you consider turning your engine backward. I avoid turning engines backward...

My vacuum pump sits on a shelf in my hangar, along with the other aviation relics... .

Fair point about vacuum pump vanes, but I have never heard from someone directly who has broken one... I don't think enough schmutz would build up to be an issue on a regularly-used engine.

[J31]

Consider your vacuum pump as you consider turning your engine backward. I avoid turning engines backward...

My vacuum pump sits on a shelf in my hangar, along with the other aviation relics... .

Fair point about vacuum pump vanes, but I have never heard from someone directly who has broken one... I don't think enough schmutz would build up to be an issue on a regularly-used engine.

I have replaced many vacuum pumps the were broken by turning the engine backward. Many had stickers that state turning backward may lead to breakage.

[ahramin]

J31 could you post a picture of this sticker please?

[photofly]

Sigma-Tek pumps can rotate either way. Tempest pumps have canted vanes and come in clockwise and anti-clockwise models. Tempest documentation has a lot of do's and don't, but among them I can find no sign of any prohibition on rotating a prop, by hand, backwards.

The debris inside a pump should be only ultra-fine dry graphite powder worn off the vanes, by design, which lubricates them. Anything bigger and the vanes are going to break at speed, in any direction. I'm having a lot of difficulty imagining any damage being caused by rotating a pump slowly in either direction, unless it was on the verge of failure already.