Warrenator
Well-known member
My wife was out working with a gas powered irrigation pump, I happened to walk by and she was just yanking on the starter cord, completely worn out and frustrated and upset. I took a quick look at it, flipped the ignition switch to "On," and it started on the first pull. It is easy for me because I've spent a lot of my life working with machines but not everyone has, so I wrote this little treatise on gas engines for her. Hopefully it will help someone else too.
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I thought it might be helpful to share the way I think about engines in general. Once one understands the way our pal, the internal combustion engine, goes about his day I think one can help him get the things he needs so he can fulfill his dream of providing you with motive power.
It all starts with FIRE. Prometheus didn't just risk the wrath of the gods to keep us warm and cook our food, but also to harness the life force of dinosaurs long gone from this earth to do useful work for us. An external combustion engine uses fire to expand something, like water is expanded into steam. The steam engine then harnesses that energy by driving a piston back and forth, which can be turned into rotary motion by a crankshaft. An Internal combustion engine does the same thing, except it uses Fire to expand Air inside the engine, which drives the piston back and forth, again turned into rotary motion by the crankshaft.
So we know we need FIRE. There are three things needed to have fire; Air, Fuel, and Heat. Take away one item and fire cannot occur. (We call this the Fire Triangle: Fuel, Air, Heat) In the internal combustion engine Fuel is gasoline. Heat is a spark provided by our ignition system. Air is provided by the piston moving back and forth in the cylinder.
So when we start a gasoline engine, we need to give it Fuel by having the gas supply turned on to the carburetor. We have Heat (Spark) by turning on the ignition system. We need to give it air by moving the piston up and down, either by electric starter motor or pulling a rope around the end of the crankshaft.
But of course each engine has a particular personality. One of these quirks is that engines don't like a lean mixture of fuel when they are cold. Hence the "Choke" on a carburetor is devised so that less air can get into the engine but more fuel, which is a richer mixture. Once the engine is running it gradually warms up and then can burn a leaner mixture, and needs more air, so we slowly open the choke (unhelpfully labeled "Start" for a rich mixture and "Run" for a lean mixture)
Choke, Throttle. Sounds a bit violent, doesn't it? The choke adjusts the mixture. the throttle adjusts the amount of air the engine can get. Closed throttle, or Turtle setting, very little air can get in. Of course it isn't all the way closed, some air gets through the carburetor, the amount can be adjusted to set the idle speed. Fully open, or Bunny, allows as much air to flow through the carburetor into the engine as possible, resulting in max power and speed.
Lovely. Our friend the engine has been given Fuel, Heat, and Air, and is now merrily spinning away providing us with power and noise and heat and precious carbon monoxide. How nice. But it is time for the engine to go back to sleep. So we can stop this merry-go-round by removing the Fire that makes it all go. Can we remove the air? Yes, by closing the throttle there is less air and the engine slows down, we could fully stop it if we wanted by removing all the air but the mechanism is difficult to access because of the air filter and so on but absolutely if we blocked the air intake with a big cork the engine would stop. Fuel? Yes, we can stop the engine this way by shutting off the fuel supply, or running it out of gas. If the engine is to be stored away for a while it is good to run the carburetor dry because gasoline is not completely pure, and when leftover gas is left in the carburetor it slowly evaporates and leaves a gummy residue that can clog the various jets and tubes inside the mechanism. Heat? Yes, that is the best and most used way to turn the engine off, just remove the Spark with the ignition switch, and the fire stops burning, the engine stops.
So when I approach an engine I ask myself what does it need to go? Fuel, Spark, Air. I make sure the fuel is on and set to a good mixture for conditions, warm or cold. Spark I get from turning the ignition on. Air I get from spinning the engine.
So I set it up, and spin the engine. Nothing. That's OK. The fuel/Air mixture is drawn from the carburetor into the engine combustion chamber by the pumping action of the piston. Might need a few tries to get enough to support combustion. Pull, pull. Still nothing. Maybe the mixture isn't perfect for conditions. Adjust it slightly and try again. Pull, pull. Not a cough. Now I'm puzzled. Check and confirm - Fuel, Spark, Air. Is there gas in the tank, and the valve turned to on? Is the ignition turned on? Adjust the carb settings and try again. Ah, there it goes. It was just being cold blooded. Poor baby, sometimes we're cranky in the morning, eh? We will slowly adjust your carburetor settings as you warm up, then you'll be ready to work.
If there is still no signs of life from the engine, time to have a friendly motor expert have a peek. They will do the same Fire Triangle checks you just did, but on a more granular level. For example, they will sniff the exhaust to smell if gas is getting through the motor, or use an alternate fuel source like a spray can of starting fluid (just ether in a can) to see if they can get the engine to run that way. They will remove the spark plug with a wrench and see if they are getting a spark. They will use a pressure gauge to see if the engine is pumping air properly. Nothing magical about it, just access to some tools and a certain willingness to take things apart.
So there you go. I hope this helps you to better get along with your small engines you might find around the farm. For the purposes of this discussion I have ignored such machines as the diesel engine and fuel injected, electronically ignited lawnmowers. And two-stroke engines such as the ones in leaf blowers and chainsaws, which are roughly the same but also like to have their gas mixed with a special oil to keep the spinny bits inside happy.
_____________
I thought it might be helpful to share the way I think about engines in general. Once one understands the way our pal, the internal combustion engine, goes about his day I think one can help him get the things he needs so he can fulfill his dream of providing you with motive power.
It all starts with FIRE. Prometheus didn't just risk the wrath of the gods to keep us warm and cook our food, but also to harness the life force of dinosaurs long gone from this earth to do useful work for us. An external combustion engine uses fire to expand something, like water is expanded into steam. The steam engine then harnesses that energy by driving a piston back and forth, which can be turned into rotary motion by a crankshaft. An Internal combustion engine does the same thing, except it uses Fire to expand Air inside the engine, which drives the piston back and forth, again turned into rotary motion by the crankshaft.
So we know we need FIRE. There are three things needed to have fire; Air, Fuel, and Heat. Take away one item and fire cannot occur. (We call this the Fire Triangle: Fuel, Air, Heat) In the internal combustion engine Fuel is gasoline. Heat is a spark provided by our ignition system. Air is provided by the piston moving back and forth in the cylinder.
So when we start a gasoline engine, we need to give it Fuel by having the gas supply turned on to the carburetor. We have Heat (Spark) by turning on the ignition system. We need to give it air by moving the piston up and down, either by electric starter motor or pulling a rope around the end of the crankshaft.
But of course each engine has a particular personality. One of these quirks is that engines don't like a lean mixture of fuel when they are cold. Hence the "Choke" on a carburetor is devised so that less air can get into the engine but more fuel, which is a richer mixture. Once the engine is running it gradually warms up and then can burn a leaner mixture, and needs more air, so we slowly open the choke (unhelpfully labeled "Start" for a rich mixture and "Run" for a lean mixture)
Choke, Throttle. Sounds a bit violent, doesn't it? The choke adjusts the mixture. the throttle adjusts the amount of air the engine can get. Closed throttle, or Turtle setting, very little air can get in. Of course it isn't all the way closed, some air gets through the carburetor, the amount can be adjusted to set the idle speed. Fully open, or Bunny, allows as much air to flow through the carburetor into the engine as possible, resulting in max power and speed.
Lovely. Our friend the engine has been given Fuel, Heat, and Air, and is now merrily spinning away providing us with power and noise and heat and precious carbon monoxide. How nice. But it is time for the engine to go back to sleep. So we can stop this merry-go-round by removing the Fire that makes it all go. Can we remove the air? Yes, by closing the throttle there is less air and the engine slows down, we could fully stop it if we wanted by removing all the air but the mechanism is difficult to access because of the air filter and so on but absolutely if we blocked the air intake with a big cork the engine would stop. Fuel? Yes, we can stop the engine this way by shutting off the fuel supply, or running it out of gas. If the engine is to be stored away for a while it is good to run the carburetor dry because gasoline is not completely pure, and when leftover gas is left in the carburetor it slowly evaporates and leaves a gummy residue that can clog the various jets and tubes inside the mechanism. Heat? Yes, that is the best and most used way to turn the engine off, just remove the Spark with the ignition switch, and the fire stops burning, the engine stops.
So when I approach an engine I ask myself what does it need to go? Fuel, Spark, Air. I make sure the fuel is on and set to a good mixture for conditions, warm or cold. Spark I get from turning the ignition on. Air I get from spinning the engine.
So I set it up, and spin the engine. Nothing. That's OK. The fuel/Air mixture is drawn from the carburetor into the engine combustion chamber by the pumping action of the piston. Might need a few tries to get enough to support combustion. Pull, pull. Still nothing. Maybe the mixture isn't perfect for conditions. Adjust it slightly and try again. Pull, pull. Not a cough. Now I'm puzzled. Check and confirm - Fuel, Spark, Air. Is there gas in the tank, and the valve turned to on? Is the ignition turned on? Adjust the carb settings and try again. Ah, there it goes. It was just being cold blooded. Poor baby, sometimes we're cranky in the morning, eh? We will slowly adjust your carburetor settings as you warm up, then you'll be ready to work.
If there is still no signs of life from the engine, time to have a friendly motor expert have a peek. They will do the same Fire Triangle checks you just did, but on a more granular level. For example, they will sniff the exhaust to smell if gas is getting through the motor, or use an alternate fuel source like a spray can of starting fluid (just ether in a can) to see if they can get the engine to run that way. They will remove the spark plug with a wrench and see if they are getting a spark. They will use a pressure gauge to see if the engine is pumping air properly. Nothing magical about it, just access to some tools and a certain willingness to take things apart.
So there you go. I hope this helps you to better get along with your small engines you might find around the farm. For the purposes of this discussion I have ignored such machines as the diesel engine and fuel injected, electronically ignited lawnmowers. And two-stroke engines such as the ones in leaf blowers and chainsaws, which are roughly the same but also like to have their gas mixed with a special oil to keep the spinny bits inside happy.
