Aviation Training Tip: Fuel Injection Systems

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1:07binders, and tracking, quizzes, logbook audits, endorsements, and more. And you can try every single one of our courses for free for as long as you would like at Wi-Fi-CFI.com. Moving on now, fuel injection. This system's much better. Like I said, most newer aircraft have fuel injection. Even some older aircraft have been retrofitted. They've gotten rid of the carburetors, and they've put in fuel injection systems. They are just much better, and they're not susceptible to this intake induction icing. With fuel injection, fuel is injected either directly into centers or just ahead of the intake valve, and they usually contain six different main components. It's obviously going to depend on what type of aircraft you're flying, but these are the main basic components of a fuel injection system. You've got your engine driven fuel pump. Obviously, we have fuel tanks. We're kind of not really including that here. So, number one, we've got our

2:08engine driven fuel pump. That's right here. Anytime that the engine's running, this engine driven fuel pump is running. It runs with the engine. The engine runs this engine driven fuel pump. If the engine is not running, this engine driven fuel pump is not running, and it is not pumping fuel from the fuel tank over to the cylinders. We also have a fuel air control unit. Right here, this is where we just get the right mixture of fuel and air together. We don't want to have way too much air or way too much fuel. This is the control unit that measures that out force. We then have the fuel manifold valve. It's usually sitting right on top of the engine here, and this is where it will distribute all out from this manifold valve through the fuel lines into the individual cylinders. A number four discharge nozzles. That's these where we're discharging that fuel and air into the cylinders. We have an auxiliary fuel pump. That's going to be number five here. The auxiliary fuel pump is typically electrically driven. What do we use the auxiliary fuel pump for?

3:15We need to use it for engine starting because we have to be able to get fuel from our fuel tank to our engine to start the engine. Then once the engine is running, our engine driven fuel pump will be running and we won't need the auxiliary fuel pump anymore. But this engine driven pump is not going to be running if the engine is not running. We have to use the electric auxiliary fuel pump, which can be run with the battery. That's why we turned the battery on before we have to turn the engine on so that we can get this guy energized and move him. There are other times that you would also use the auxiliary fuel pump in emergencies, in emergency situations, say the engine driven fuel pump failed. Then you can turn on your up in flight and for whatever reason, this component fails. You can go ahead and turn on your auxiliary pump and it's hopefully in, you know, a good world. It will turn on and pump fuel the engine. Also, you're going to want to check your specific aircraft's POH or AFM to see the times that the aircraft manufacturer says you should turn on the auxiliary fuel pump. It's going to depend on

4:18what airplane you're flying, but sometimes they will say it needs to be on for like takeoff and it needs to be on for climb and it needs to be turned on for landing or it needs to be turned on for certain maneuvers like steep turns, but there will be a list usually like in the limitations section or it could be in the system section of the pH where they tell you the other times that this auxiliary fuel pump should be on. Check in the checklist section as well. The normal operations section, the emergency operations section, look through those. Checklists that they have printed out or that they've typed up and know when you're supposed to use this because it will vary based on what aircraft you're flying. And then number six is fuel pressure and fuel flow indicators. It's not depicted on this little chart here, but that is what we would see inside the cockpit. We'll have fuel gauges inside the cockpit. We'll have fuel pressure. We'll have fuel flow and we'll have fuel quantity indicators in the cockpit. So after starting, this provides number one engine driven fuel pump right after starting this provides pressure to move the

5:22fuel from the tank to the fuel air controller unit. This is where it's mixed. This is kind of all the things we just talked about. So I'll just go ahead and put up these descriptions here, but we just talked about all this stuff. Fuel injection advantages reduction in evaporative icing. Without a carburetor, you're not getting carb ice. It says reduction in evaporative icing. Maybe you could still get ice in this system. Let me maybe it's something you could be aware of, but pretty unlikely. You're going to have any problems with icing and a fuel injection system. You have better fuel flow. This fuel air control unit works very, very well. It makes the fuel flow more. It makes the fuel mixture more precise. So you're not wasting fuel. That's why you're going to get better fuel flow. Faster throttle response. This whole system works much, much quicker than a carburetor. If you add power or mixture whatever in a carburetor, it takes some time to lower that pressure in the mid-chury to suck out more air or to suck out more fuel with more air and get more

6:25power. This whole system does it a lot more quickly. Precise control of the mixture. You have a little bit better mixture control. Better fuel distribution and easier cold weather starts. Those are the advantages. Some disadvantages of a fuel injection system. It's not all perfect. Can't all be perfect. There's always pros and cons. Difficulty in starting a hot engine. Vapor locks during ground operations on hot days and problems restarting an engine that quits because of fuel starvation. Let's talk about what vapor lock is. I'm going to back this up just a little bit so you can see our picture a little better. What vapor lock is is when vapor essentially gets into the system somehow. What typically happens is you can see you've got our fuel intake manifold. You've got these fuel lines that are running right over the top of this engine. They're running around this engine and into the cylinders. These can get very hot and they can vaporize

7:26the fuel because this engine gets very, very hot. If it vaporizes fuel, then you're not getting the right fuel air mixture into your cylinders and that's a problem. That can be a problem with losing power or even starting an engine. If it's really, really hot on the ground to say you've got an engine with a fuel injection system. This airplane just went flying. It landed. It came back and it parked. It's got a very hot engine. It's a very hot day. The next pilots to go in say they're going in 10, 15 minutes later. They're going to hop in the plane and go on the next flight. It can be hard to start this engine because these fuel lines are so hot and without good cooling, they can vaporize the fuel that's in here and that can lock up the fuel flow. That's what vapor lock is and that's why it is difficult or it can be difficult to start these on the ground. Once you're in the air typically with fuel injection systems, you've taken off,

8:28you've climbed up, you're at cruise or whatever. You're getting enough airflow typically just from the movement of your airplane to get enough cooling over these lines that they're not probably going to vapor lock and fly. Am I going to say it's never going to happen? No, I'm not going to say that. I wouldn't say that. Maybe it could happen. But for the most part, when you're flying, you have enough air for cooling these lines. But when you're taxing or doing your run-up, you could vapor lock if it's a very, very hot day. You're taxing around maybe with a very lean mixture, a very high power setting. It's a hot day outside. You could experience this vapor lock. So what do you do? Increase some of the mixture to cool it down a little bit, bring some power back so you're not running this thing at full power. Try to park the aircraft so it's directed into the air. If there's wind that day, try to face your airplane into the wind so you're getting a little bit more cooling coming in and cooling these lines down.