Starting the Lycoming IO-360

Starting an airplane engine is not like starting a modern car. The engine in the Cardinal is a fuel injected Lycoming IO-360. Unlike automotive engines fuel injected aircraft engines are actually often harder to start than their carbureted cousins – especially when the engine is already warm.

The cooling airflow on an aircraft engine flows into the cowling above the engine, down past cooling fins, and out the bottom. This means that during flight the coolest part of the cowling is above the engine. Of course, once parked with a hot engine the top of the cowling is the hottest part because heat rises. Since it is more important to avoid any issues with vapor lock in flight than on the ground the fuel injector lines are positioned above the engine. This eliminates any issues with vaporize fuel in the lines in flight.

On the ground with the engine warm this is an impediment. As heat rises off of the engine first the fuel expands and some of it that remains in the lines dribbles out of the injectors into the intake manifold. This leaves the mixture in the manifold too rich to start. And of course this also leaves vapor in the lines. So there is a different procedure to follow in the Cardinal for warm and cold starts after confirming that the fuel selector is on both and the cowl flaps are open.

For a cold start: Move the mixture handle and throttle full forward (mixture rich, throttle full open). Turn on the master switch then operate the electric boost pump for several seconds. I choose a time varying between 3 and 5 seconds depending on the outdoor temperature. Then move the mixture to idle cut-off and the throttle to approximately a quarter of an inch. With hand on the throttle crank until the engine starts then slowly advance the mixture after adjusting the throttle as needed.

For a warm start: No priming! The intake manifold already has a rich mixture in it. Instead, move the mixture to idle cut off and throttle a quarter of an inch. Start cranking for a few seconds. If the engine has not started start slowly advancing the throttle to search for the mixture point where it will light off. Once it starts, pull the throttle back to 1200 RPM and advance the mixture forward. It will take several more blades (rotations of the prop) for the engine to start but that is normal for a warm start.

After starting pull the mixture back to lean for all ground operations to prevent any issues with plug fouling. This can be done quite aggressively and many advocate a lean point where even advancing the throttle for take off will cause the engine to stumble and quit. This also eliminates the chance that you will accidentally take off with a mixture that is too lean.

As you can see starting a fuel injected aircraft engine takes three hands! You’ll learn the techniques that work best for your particular aircraft. But most Lycoming fuel injected engines start similar to this. It isn’t anything to be afraid of and after a few starts you will be an expert. Make sure you don’t over prime, especially when warm!

3 thoughts on “Starting the Lycoming IO-360

  1. Jim Howard

    I use the hot start technique I learned from the Cardinal Flyers Online site. It works 100% of the the time.

    1) If you know you are going to hot start when you shut down, set the rpm at 1200rpm and pull the mixture all the way to cut off.

    Turn off the mags and master, lock the door, walk away.

    When you get back and the engine is still hot.

    1) If you forgot to set 1200rpm when you shut down, then open the throttle 1/4 inch, otherwise DON’T TOUCH THE THROTTLE. DON’T TOUCH THE MIXTURE.

    2) Run the before start checklist. DON’T TOUCH THE THROTTLE OR MIXTURE.

    3) Place your hand near the mixture control, but DON’T TOUCH THE THROTTLE OR MIXTURE.


    5) After 3 to 5 blades the engine will begin to fire. DON’T TOUCH THE THROTTLE. Keep turning the engine with the key as you ease the mixture towards rich.

    6) As the engine starts ease the mixture a bit more. The engine will spin up to about 1300-1500rpm. Ease the throttle back, enrichen the mixture as needed to get a smooth idle, but as you correctly point out, don’t set it any richer than needed.

    This works every time, here in Texas where it is very hot all summer.

  2. Dan Post author

    This sounds like an excellent technique! I do remember reading it on the CFO website but haven’t tried it yet for a particular reason. Guy Maher taught me a slightly different shutdown technique during my transition training which adds pulling the throttle to fully closed after the mixture is at cut-off and the prop is slowing down. This avoids the typical shudder as the high compression engine shuts down but also means that the throttle isn’t left at the 1200 RPM point.

    I’ll try and remember to do some shutdowns the more typical way leaving the throttle alone so I can try this hot-start technique! Thanks!

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