Really cold start C152?

[Cap'n Jack]

Last Monday, I tried to start a C152 at 15°F (after a fast preflight). It was preheated. Battery seemed good- it would start on the prime after one blade but wouldn't keep running. After 5 or 6 attempts, I had the FBO put the plane away. It was a rental & I didn't want to run the battery down. The owner placed cold start insructions in the plane ant I think I followed them.

The instructions suggested 5-10 pumps of prime. After I came in and told the FBO to put the plane back, I was talking to one of the local charter pilots. He suggested I was to pump the primer while running the starter.

Anyone else have any thoughts on this? It's usually much warmer when I fly...
Thanks in advance!

 

[bbchien]

Do the whole thing with Carb Heat ON. This lenghens the draught tube and slightly richens the mix a little more.

Taught to me by Francis Einarson, retired principal of the Einarson Flying Service, Int'l Falls MN.

 

[tonycondon]

5-10 shots of prime seems like a lot. it has a Tanis type heater and all the cylinders were warm on the preflight? priming while cranking does help sometimes when its really cold. bruce's carb heat suggestion is also good.

 

[Cap'n Jack]

I tried the carb heat- no joy. After the prime ran out it would shut down. I don't think it ran long enough to warm the air.

I suppose next time I'll prime while cranking- maybe that's what was meant. I never had to prime more than 3 shots before.

What happens to the extra fuel if one primes too much?

 

[rmciottijr]

You could of had water in the fuel lines that froze and blocked the fuel flow. When you use prime it bypasses the carburetor and inject the fuel directly into the engine.

 

[KennyFlys]

On the Cutlass, I back-prop at least five times and hit the prime once for each rotation. It's never failed for me.

 

[tonycondon]

back-prop?

 

[jesse]

Are you talking 82U? I have started it at colder temperatures. My technique is to prime it, hit the starter, prime and pump at the same time while it is cranking. It'll cough to life BUT IT WILL NOT STAY RUNNING unless you keep priming and keep pumping the throttle. The more hands you have the better. It will start.

 

[KennyFlys]

back-prop?

Rotating backward?

 

[bbchien]

Are you talking 82U? I have started it at colder temperatures. My technique is to prime it, hit the starter, prime and pump at the same time while it is cranking. It'll cough to life BUT IT WILL NOT STAY RUNNING unless you keep priming and keep pumping the throttle. The more hands you have the better. It will start.

That's a fabulous mental image....

 

[tonycondon]

interesting, ive never heard that as a method for helping start a warm or cold engine. have you ever tried just priming it without the prop rotations and see if it makes a difference?

 

[KennyFlys]

interesting, ive never heard that as a method for helping start a warm or cold engine. have you ever tried just priming it without the prop rotations and see if it makes a difference?

Ahhh.. that's part of cold-starting...

From the 172RG POH:

Prior to starting on cold mornings, it is advisable to pull the propeller through several times by hand to "break loose" or "limber" the oil, thus conserving battery energy.

 

[tonycondon]

fair enuf

i guess i usually just let the starter do the work for me.

 

[KennyFlys]

fair enuf

i guess i usually just let the starter do the work for me.

If it were 0F instead of just 0C, I'd probaly be lazy, too.

Fortunately, we have a heater and generator out on the ramp. The nice thing is mornings haven't as bad since I started flying traffic.

 

[stingray]

When it is cold I prime 2 pumps no more. Then pump the throttle while cranking. Keep pumping the throttle or it will quit. After 15 to 30 sec it will keep running. I always preheat but when it is cold this is the only way it will run. I thought the fuel had water in it also that is why it wouldn't run, but pumping the throttle seemed to work so no water was frozen. My 150 will start even cold on 1/2 of a primer pump it just will not stay running. Best is to prime less and pump more.

Dan

 

[jesse]

Right Dan. The main thing is you need to stay on the pumping or else it won't stay running. It can take awhile.

 

[Rob Schaffer]

Last saturday I had some trouble starting the 152 for my training flight too. It was about 24 degrees out. I was the first flight of the morning and the frost had just melted off the wing (plane was moved into the sun)

I did the normal 3 shots of primer and then cranked..... nothing. I did one additional prime, and cranked again,... little better, but no go. My instuctor opened the carb heat and we added a little more throttle,... primed 1 1/2,... and turned the key to start. While cranking, I added the remaining 1/2 primer and she kicked right over.

Ran through the full checklist and then sat for a few more minutes talking about the instruments (pitot, static dependent, vacuum dependent) so the oil and engine could warm up.

 

[Dean]

At 15 degrees, my happy butt is in front of the fire, not trying to start an airplane.

 

[steingar]

Most of the people who suggest such crazy starting techniques don't actually own the aircraft, and I imagine would not do such things on their own. My aircraft gets a preheat until the engine is warmed up, no matter how long it takes. After that it starts just fine.

 

[RMCN172RG]

I was getting different thoughts from people on cold starting my 172RG. My CFI at PHN recommended turning the prop through a couple of times to distribute some oil but not the priming while doing it.

I also asked my A&P. I have the plane hangared, unheated with him as well. Suggestion was to pre-heat it.

At the flight school at PTK they kept the planes pluggged in, Tanis heaters and cowl plugs in all winter and just used the normal starting procedure.

I read in magazines earlier this winter that the pulling the prop through does not help a lot.

I have added a oil pan heater this year but have not flown the plane since 12/21. With the annual finishing a week ago and the lovely Michigan weather this winter. Maybe I'll get to try it this weekend

 

[Cap'n Jack]

Are you talking 82U? I have started it at colder temperatures. My technique is to prime it, hit the starter, prime and pump at the same time while it is cranking. It'll cough to life BUT IT WILL NOT STAY RUNNING unless you keep priming and keep pumping the throttle. The more hands you have the better. It will start.

Yes- it was 82U. It would start right up but wouldn't keep running. I am now thinking, based on what I read above, that the instructions meant for me to keep priming as it started.

Thanks much!

 

[Cap'n Jack]

At 15 degrees, my happy butt is in front of the fire, not trying to start an airplane.

/\ /\
l l
l l
Not a dedicated aviator

In cold wx:

• easier to book the rental
• no one is needing the plane as soon as you land
• less traffic since fewer people are flying
• less turbulance from warming
• even a C152 shows good performance in nice dense air

 

[steingar]

I keep a pair of buku space heaters in the hangar. They get plugged into the cowl and turned on. I go to a nice, warm Bob Evans for breakfast, and when I come back engine is heated up. I throw a space heater inside the cockpit, and by the time I'm done with the preflight the cockpit is nicely warmed up too.

No way would I keep the engine warm all winter. I'd rather keep any moisture in the engine in solid form, to be purged when the thing warms up in flight. Ice doesn't corrode metal, water does.

 

[MarkL]

Yes- it was 82U. It would start right up but wouldn't keep running. I am now thinking, based on what I read above, that the instructions meant for me to keep priming as it started.

Thanks much!

I will also mention that i've had to constantly pump 82U to start on cold days, actually it was around 20 degrees the one time I had to do that. When any plane doesn't want to start, read the POH, full of wonderful little tidbits.

 

[jason]

Yes- it was 82U. It would start right up but wouldn't keep running. I am now thinking, based on what I read above, that the instructions meant for me to keep priming as it started.

Thanks much!

Just to clarify, I think that most people are saying that they pump the throttle to keep it running...as opposed to continued priming. I've used both, but pumping the throttle is usually a little bit easier and normally does the trick.

 

[jason]

Most of the people who suggest such crazy starting techniques don't actually own the aircraft, and I imagine would not do such things on their own. My aircraft gets a preheat until the engine is warmed up, no matter how long it takes. After that it starts just fine.

You can't really compare the two worlds (ownership and renting). For instance, if I was being charged a tach dry rate, I'd run at 65-75% power...but they don't...so I'll cruise as fast as the POH will allow.

That's not to say that I don't respect the airplanes. I wouldn't ever do anything that I felt was truly damaging to the aircraft. It's just not as easy to do some things when you're renting and you don't have a nice hanger to work in...and all of the tools right there.

 

[pilotmattk]

Just to clarify, I think that most people are saying that they pump the throttle to keep it running...as opposed to continued priming. I've used both, but pumping the throttle is usually a little bit easier and normally does the trick.

I'm pretty sure pumping the throttle is bad advice. That just drains fuel straight into the carb. In that situation a slightest bit of backfire can cause a carb fire, and then you REALLY need to keep it cranking and hope it gets sucked in.

Priming on a carbureted engine usually puts fuel in the vertical riser above the carb (intake manifold). This combined with the fact the carb is mostly shut greatly reduces your chances of a fire outside the engine.

Correction: According to my 152 POH the primer puts fuel into the cylinder intake ports. That's even farther up in the system. Each plane is different, but priming safer than pumping the throttle.

 

[tonycondon]

matt - that would be true if the engine was not running. I believe the discussion is that the engine starts running but requires about 30 seconds of throttle pumping to keep going and get warmed up. As long as the engine is running it will suck the fuel/air mixture up into the intake and a backfire fire shouldnt be a problem.

 

[pilotmattk]

Woops, I did read that wrong. Sorry FlyNE. At the top of the thread it didn't seem like the engine was running, but by the end I guess it was? Anyway, I have pumped throttle once it's running too.

I once knew an instructor who was insistent that the "proper" way to start a 152 was to pump the throttle first. (and I didn't want to do it!)

-Matt

 

[Cap'n Jack]

Matt-

The thread is a bit confusing. the engine wants to run and fires off the prime, but doesn't keep running. The plane's owner left instructions but it seems I read them differently than intended. I shared your concern for creating a puddle of fuel that could create a fire.

 

[Dean]

/\ /\
l l
l l
Not a dedicated aviator

I am a dedicated aviator,to a certain degree, and that degree is above freezing. Freezing my fingers and toes off is not fun. So if it is below freezing, the airplane is going to sit and so am I, by a nice warm fire.

 

[flyingcheesehead]

Do the whole thing with Carb Heat ON. This lenghens the draught tube and slightly richens the mix a little more.

Taught to me by Francis Einarson, retired principal of the Einarson Flying Service, Int'l Falls MN.

What Bruce said. Coldest I started the 182, it was exhibiting symptoms like you described. The only way I could keep it running was to turn on the carb heat. I let it run on the ground for ~20 minutes before it'd run without the carb heat on.

Also, I never prime more than one shot without cranking. On some engines, if you're not cranking it'll simply drip out.

 

[Cap'n Jack]

Do the whole thing with Carb Heat ON. This lenghens the draught tube and slightly richens the mix a little more.

Taught to me by Francis Einarson, retired principal of the Einarson Flying Service, Int'l Falls MN.

What Bruce said. Coldest I started the 182, it was exhibiting symptoms like you described. The only way I could keep it running was to turn on the carb heat. I let it run on the ground for ~20 minutes before it'd run without the carb heat on.

Also, I never prime more than one shot without cranking. On some engines, if you're not cranking it'll simply drip out.

I'm not disagreeing- just learning. I beleive that the carb heat uses air warmed by the exhaust (probably a shroud) to heat the incoming air. The air is warmer, thus less dense, which enrichens the mixture.

How does using carb heat help on initial start? I imagine the it helps after the engine is running a short time since heat is available.

 

[flyingcheesehead]

I'm not disagreeing- just learning. I beleive that the carb heat uses air warmed by the exhaust (probably a shroud) to heat the incoming air. The air is warmer, thus less dense, which enrichens the mixture.

How does using carb heat help on initial start? I imagine the it helps after the engine is running a short time since heat is available.

My working theory at the time was that there had been frozen moisture in the induction air filter. Since the carb heat bypasses the filter, the engine could breathe freely. Eventually the engine heat unfroze the filter. But, that's only a theory.

 

[ScottM]

I'm not disagreeing- just learning. I beleive that the carb heat uses air warmed by the exhaust (probably a shroud) to heat the incoming air. The air is warmer, thus less dense, which enrichens the mixture.

That is true once the engine is up and running but it does not explain how it really helps a cold engine, one in which the exhaust is not hot as there is no hot exhaust as a result of a lack of combustion.

How does using carb heat help on initial start? I imagine the it helps after the engine is running a short time since heat is available.

Bruce has his theory, I don't really know how or if it does on start.

 

[bbchien]

That is true once the engine is up and running but it does not explain how it really helps a cold engine, one in which the exhaust is not hot as there is no hot exhaust as a result of a lack of combustion.

Bruce has his theory, I don't really know how or if it does on start.

If you have suction in a long tube vs. in a short one, there will be more of a pressure drop over the long tube. The pressure drop in the long tube (intake with carb heat engaged) lowers MP a bit, making the fraction of vaporized fuel higher. It's independent of there being any manifold warmth (there isn't any warmth at 10F).

I don't know if Francis Einarson's explanation is what really happens, but it seems to help- a lot.

 

[n20junkie]

crank and prime, crank prime. Priming before cranking, just causes fuel to spray on the valves and run out.