Engineer Ted's Hot Start Procedures for Injected Lycomings and Continentals

[Ted]

As long as there have been fuel injected aircraft engines, there have been arguments on the best way to hot start the things, and the primary consensus is that hot starting them is annoying, and for many, relatively inconsistent. You've probably heard dozens of techniques for hot starts, you may have tried them, and you may have found that some of them work, but not very well. Maybe you've found one that works on your plane, but not on others. Certain aircraft engines have minor differences in their designs that can impact how well or poorly a particular technique works.

The hot start techniques I use have been proven over thousands of hours, across multiple aircraft for each manufacturer. Top induction, top exhaust, bottom induction and exhaust, turbocharged, naturally aspirated, it really doesn't matter. A number of PoA members (and others) have also attempted to hot start a plane with me in it, and after their technique doesn't work, I ask to use mine, which works >99% of the time. I say >99% and not 100% because none of these work 100% of the time, sometimes you get just the right combination of circumstances that the engine doesn't want to start and you have to try something out.

I should start out by mentioning a some things:

1) A lot of times, starting troubles are as much (or more) a weak ignition rather than starting technique. Are your plugs old? Are they Tempest plugs? (if they aren't, buy Tempest) Condition of your ignition harnesses? Magnetos? A good ignition system will help starting, and everything else. Electronic magnetos should provide a better start during cranking and improve hot starts (and cold starts).

2) If your engine is cranking slowly, this will also make hot starts hard, and on Continentals can end up damaging/breaking your starter adapter. Make sure your batteries and battery cables are in good condition. If they are original, replace them. If they're aluminum, replace them with copper.

3) Lycomings and Continentals have different starting techniques, because their fuel injection systems are completely different in design. A hot start technique, in order to work, needs to properly accommodate the fuel injection system that it's working for. I'm not going to go into the design of each fuel injection system.

4) These apply to mechanically fuel injected engines. Not carburetors, not pressure carburetors (such as used on the original 310s), not FADEC or electronic engine control engines - mechanical injected engines. So for example, an IO-540-C4B5, TIO-540-J2BD, TSIO-520-NB, IO-520-E, etc.

Now, my starting techniques.

Lycoming hot start technique:

1) Throttle and prop full, mixture at idle cut-off
2) Turn on fuel pump
3) Push the mixture to full rich for ~8 seconds
4) Pull the mixture back to idle cut-off
5) LEAVE THE FUEL PUMP ON
6) At this point, you should have the fuel pump on, throttle and prop full forward, mixture at idle cut-off
7) Start cranking the engine. When it catches, push the mixture forward (not slowly, but not quickly) and pull the throttle back relatively quickly. With practice, you'll get the timing right.

On my Aztec, I was able to get this such that a hot start would settle right into a 600-900 RPM idle most of the time

Continental hot start technique:

1) Throttle, prop, and mixture all full forward
2) Fuel pump on prime (high pressure/flow) for about 4 seconds (similar to a prime for a cold start)
3) Fuel pump off
4) Start cranking the engine. While cranking, pull the throttle back slowly (slow enough that it's about 5 seconds from full forward to idle). When it catches, you may have to accelerate how quickly you pull the throttle back to prevent it from revving too high. Normally, it catches by 1/4 throttle.

Alternate Continental hot start technique (which I've only had to use a few times - use technique 1 first):

1) Throttle, prop, and mixture all full forward
2) Fuel pump on prime (high pressure/flow) for about 8 seconds (similar to the Lycoming hot start)
3) Fuel pump off
4) Mixture to idle cut-off
5) At this point, you should have fuel pump off, mixture at idle cut-off, throttle and prop full forward
6) Start cranking the engine. When it catches, push the mixture forward and then throttle back, similar to a Lycoming hot start

The primary Lycoming and Continental starts should work for virtually all engines, virtually all of the time.

As I tell everyone who I tell these techniques to: if you have a technique that works for you and you're happy with for your plane/engine combination, keep using it. My techniques are not the only ones that work and they may not be the best on your engines. But, in my experience they do work well and consistently. I put in guidelines for timing, but you'll get the feel of it after a while. As I implied above on some of the things to check if you have hot start issues (or many other issues), general engine/airplane condition are important. No amount of good technique will overcome a starter cable that's broken.

 

[robin ardoin]

Thank you, Ted.

 

[MooneyDriver78]

Your Lycoming technique is for a flooded engine, why not just try the don’t touch anything approach which works the great majority of time?

 

[ArrowFlyer86]

Lycoming hot start technique:

1) Throttle and prop full, mixture at idle cut-off
2) Turn on fuel pump
3) Push the mixture to full rich for ~8 seconds
4) Pull the mixture back to idle cut-off
5) LEAVE THE FUEL PUMP ON
6) At this point, you should have the fuel pump on, throttle and prop full forward, mixture at idle cut-off
7) Start cranking the engine. When it catches, push the mixture forward (not slowly, but not quickly) and pull the throttle back relatively quickly. With practice, you'll get the timing right.

Thanks, Ted.
Gracefully doing step #7 is not easy (at least for me). Three tasks with two hands: LH turning key to start, RH trying to advance mixture and reduce throttle.
I've seen people do it well (my CFI for one), but they have a better feel for when the engine "catches" and they can move their LH off the key and over to the throttle and move the levers more easily in a synchronized fashion.
With almost 700h in mine - I still haven't mastered that lol. I still look pretty clumsy using that method with the engine running at high RPMs longer than I'd like.

 

[Checkout_my_Six]

IMHO....most of these starting issues is a weak ignition system.

Once I rebuilt my ignition system in the TSIO-520D....it starts easily hot with no weird tricks. I replaced plugs with Tempest fine wires, replaced the leads, and rebuilt the mags with new points.

 

[Jim K]

Your Lycoming technique is for a flooded engine, why not just try the don’t touch anything approach which works the great majority of time?

Well, steps 1-3 flood the engine, so then you HAVE to use the flooded start procedure. I suspect you & I are doing the same thing...

The Lycoming/Bendix system doesn't have a return line, so you can't flush the vapor out of the system except into the cylinders, which is what Ted's procedure does. In my (admittedly MUCH more limited) experience, it's harder to start a flooded engine. Then when you do, you usually wind up with it revving way up, which is really hard on a cold engine, and is exacerbated by a bunch of extra fuel having washed down the cylinder walls.

My suggestion for hot starting a NA Lycoming io-360/540 is:
1) throttle just cracked like a normal start, prop full, mixture ico
2) boost pump on
3) crank. The engine will start after 5-10s of cranking and you jam the mixture forward quickly to keep it running
3A) if the engine didn't start, it's not that hot and it needs a little bit of a prime, about half a much as a cold start

BTW, that's the procedure from my poh, which is a good resource for operating an airplane, as it turns out.

 

[Ted]

Your Lycoming technique is for a flooded engine, why not just try the don’t touch anything approach which works the great majority of time?

As I said, do what works for you. I didn't find that the "don't touch anything" approach worked regularly or consistently.

The purpose behind this is that many pilots struggle with complicated techniques that work some percentage of the time that is well under 90%. These techniques have worked for me >99% of the time across a multitude of engines.

Thanks, Ted.
Gracefully doing step #7 is not easy (at least for me). Three tasks with two hands: LH turning key to start, RH trying to advance mixture and reduce throttle.
I've seen people do it well (my CFI for one), but they have a better feel for when the engine "catches" and they can move their LH off the key and over to the throttle and move the levers more easily in a synchronized fashion.
With almost 700h in mine - I still haven't mastered that lol. I still look pretty clumsy using that method with the engine running at high RPMs longer than I'd like.

And, again, do what works for you. You're correct, the approach requires something of a 3-handed technique. The goal is definitely not to be at a high RPM.

 

[Pinecone]

Your alternate for Continental is a Flooded Start. It works, but if you over prime, you can have fuel dripping out of the engine and a fire hazard.

I used to use this method all the time, but have reconsidered due to the fire risk.

 

[Mxfarm]

Ted,

Curious, ignition harness - one thing that's always bugged me is zip tying all leads together in a bundle - is this really ok on a aircraft? Are the mags that low of energy, or are the cables that great?

 

[Ted]

Ted,

Curious, ignition harness - one thing that's always bugged me is zip tying all leads together in a bundle - is this really ok on a aircraft? Are the mags that low of energy, or are the cables that great?

It's really only a problem if you have issues with the shielding, in which case you should replace them anyway. I'd rather see some wire holders that keep the wires separated, but it's not been an issue.

 

[flyingcheesehead]

Thanks Ted - This should have been the first sticky the forum ever had!

 

[rwellner98]

1) A lot of times, starting troubles are as much (or more) a weak ignition rather than starting technique. Are your plugs old? Are they Tempest plugs? (if they aren't, buy Tempest) Condition of your ignition harnesses? Magnetos? A good ignition system will help starting, and everything else. Electronic magnetos should provide a better start during cranking and improve hot starts (and cold starts).

emags made a night and day difference in my case. I wish I had known this before my mags finally needed overhaul/replacement and I learned it by accident.

 

[Racerx]

Thanks, Ted.
Gracefully doing step #7 is not easy (at least for me). Three tasks with two hands: LH turning key to start, RH trying to advance mixture and reduce throttle.
I've seen people do it well (my CFI for one), but they have a better feel for when the engine "catches" and they can move their LH off the key and over to the throttle and move the levers more easily in a synchronized fashion.
With almost 700h in mine - I still haven't mastered that lol. I still look pretty clumsy using that method with the engine running at high RPMs longer than I'd like.

A recently gone west pilot friend of mine used to say..."I've got a third leg, but not a third hand"

 

[GLMS_NC]

For Continental drivers, here is a good video and explanation of why our engines behave the way they do on hot starts.

 

[Skip Miller]

Well, steps 1-3 flood the engine, so then you HAVE to use the flooded start procedure. I suspect you & I are doing the same thing...

The Lycoming/Bendix system doesn't have a return line, so you can't flush the vapor out of the system except into the cylinders, which is what Ted's procedure does. In my (admittedly MUCH more limited) experience, it's harder to start a flooded engine. Then when you do, you usually wind up with it revving way up, which is really hard on a cold engine, and is exacerbated by a bunch of extra fuel having washed down the cylinder walls.

My suggestion for hot starting a NA Lycoming io-360/540 is:
1) throttle just cracked like a normal start, prop full, mixture ico
2) boost pump on
3) crank. The engine will start after 5-10s of cranking and you jam the mixture forward quickly to keep it running
3A) if the engine didn't start, it's not that hot and it needs a little bit of a prime, about half a much as a cold start

BTW, that's the procedure from my poh, which is a good resource for operating an airplane, as it turns out.

 

[sansoneservices]

As long as there have been fuel injected aircraft engines, there have been arguments on the best way to hot start the things, and the primary consensus is that hot starting them is annoying, and for many, relatively inconsistent. You've probably heard dozens of techniques for hot starts, you may have tried them, and you may have found that some of them work, but not very well. Maybe you've found one that works on your plane, but not on others. Certain aircraft engines have minor differences in their designs that can impact how well or poorly a particular technique works.

The hot start techniques I use have been proven over thousands of hours, across multiple aircraft for each manufacturer. Top induction, top exhaust, bottom induction and exhaust, turbocharged, naturally aspirated, it really doesn't matter. A number of PoA members (and others) have also attempted to hot start a plane with me in it, and after their technique doesn't work, I ask to use mine, which works >99% of the time. I say >99% and not 100% because none of these work 100% of the time, sometimes you get just the right combination of circumstances that the engine doesn't want to start and you have to try something out.

I should start out by mentioning a some things:

1) A lot of times, starting troubles are as much (or more) a weak ignition rather than starting technique. Are your plugs old? Are they Tempest plugs? (if they aren't, buy Tempest) Condition of your ignition harnesses? Magnetos? A good ignition system will help starting, and everything else. Electronic magnetos should provide a better start during cranking and improve hot starts (and cold starts).

2) If your engine is cranking slowly, this will also make hot starts hard, and on Continentals can end up damaging/breaking your starter adapter. Make sure your batteries and battery cables are in good condition. If they are original, replace them. If they're aluminum, replace them with copper.

3) Lycomings and Continentals have different starting techniques, because their fuel injection systems are completely different in design. A hot start technique, in order to work, needs to properly accommodate the fuel injection system that it's working for. I'm not going to go into the design of each fuel injection system.

4) These apply to mechanically fuel injected engines. Not carburetors, not pressure carburetors (such as used on the original 310s), not FADEC or electronic engine control engines - mechanical injected engines. So for example, an IO-540-C4B5, TIO-540-J2BD, TSIO-520-NB, IO-520-E, etc.

Now, my starting techniques.

Lycoming hot start technique:

1) Throttle and prop full, mixture at idle cut-off
2) Turn on fuel pump
3) Push the mixture to full rich for ~8 seconds
4) Pull the mixture back to idle cut-off
5) LEAVE THE FUEL PUMP ON
6) At this point, you should have the fuel pump on, throttle and prop full forward, mixture at idle cut-off
7) Start cranking the engine. When it catches, push the mixture forward (not slowly, but not quickly) and pull the throttle back relatively quickly. With practice, you'll get the timing right.

On my Aztec, I was able to get this such that a hot start would settle right into a 600-900 RPM idle most of the time

Continental hot start technique:

1) Throttle, prop, and mixture all full forward
2) Fuel pump on prime (high pressure/flow) for about 4 seconds (similar to a prime for a cold start)
3) Fuel pump off
4) Start cranking the engine. While cranking, pull the throttle back slowly (slow enough that it's about 5 seconds from full forward to idle). When it catches, you may have to accelerate how quickly you pull the throttle back to prevent it from revving too high. Normally, it catches by 1/4 throttle.

Alternate Continental hot start technique (which I've only had to use a few times - use technique 1 first):

1) Throttle, prop, and mixture all full forward
2) Fuel pump on prime (high pressure/flow) for about 8 seconds (similar to the Lycoming hot start)
3) Fuel pump off
4) Mixture to idle cut-off
5) At this point, you should have fuel pump off, mixture at idle cut-off, throttle and prop full forward
6) Start cranking the engine. When it catches, push the mixture forward and then throttle back, similar to a Lycoming hot start

The primary Lycoming and Continental starts should work for virtually all engines, virtually all of the time.

As I tell everyone who I tell these techniques to: if you have a technique that works for you and you're happy with for your plane/engine combination, keep using it. My techniques are not the only ones that work and they may not be the best on your engines. But, in my experience they do work well and consistently. I put in guidelines for timing, but you'll get the feel of it after a while. As I implied above on some of the things to check if you have hot start issues (or many other issues), general engine/airplane condition are important. No amount of good technique will overcome a starter cable that's broken.

Thanks for the detailed information. My lyco with Bendix injection hot starts best with mixture cut-off, 1/3 throttle.. when it starts toss in normal mixture

 

[William Pete Hodges]

My suggestion for hot starting a NA Lycoming io-360/540 is:
1) throttle just cracked like a normal start, prop full, mixture ico
2) boost pump on
3) crank. The engine will start after 5-10s of cranking and you jam the mixture forward quickly to keep it running
3A) if the engine didn't start, it's not that hot and it needs a little bit of a prime, about half a much as a cold start

BTW, that's the procedure from my poh, which is a good resource for operating an airplane, as it turns ouout.

I use nearly the same procedure but I crack open the throttle about double for hot start than for cold. It usually starts right up but if it doesn’t start after a few seconds I goose the mixture once to give it a quick shot of fuel. It fires up every time.

 

[MooneyDriver78]

I use nearly the same procedure but I crack open the throttle about double for hot start than for cold. It usually starts right up but if it doesn’t start after a few seconds I goose the mixture once to give it a quick shot of fuel. It fires up every time.

Define “goose”; full mixture, half mixture, boost pump?

 

[ja_user]

When shutting down, I put it at 1,000 rpm and remove the fuel from the equation. When starting, I reintroduce the fuel.

I don’t know why everyone gets in and moves the throttle all over the place when they just had it at 1,000 during The shutdown.

Flooding it and then doing a flooded start seems to be SOP in a few particular tail numbers, if they’ve been sitting a bit and heat soaked..

 

[William Pete Hodges]

Define “goose”; full mixture, half mixture, boost pump?

I quickly move the mixture full on and full off. Like a pump of the accelerator in a car.

 

[Datadriver]

The technique can vary slightly for the same aircraft model built in the same year. My best guess is subtle differences in firewall installs/hose routings.

 

[Greg Bockelman]

I quickly move the mixture full on and full off. Like a pump of the accelerator in a car.

What does that accomplish?

 

[William Pete Hodges]

What does that accomplish?

Carburetors have a pump tied to the throttle lever. It pumps a squirt of fuel as the throttle is opened to prevent over leaning as the air rushes in. As the new airflow stabilizes the fuel flow through the venturi catches up and the extra squirt of fuel is no longer needed. In a car or truck it is commonly called an accelerator pump. It prevents engine stalling when you push the gas pedal, especially when leaving a stoplight or manually shifting gears.

You don't have to move the throttle fully, a third of a pump will do nicely. I first learned how to do this when starting a 1950 Chevy pickup with a foot pedal to operate the starter. The starter pedal button is to the right beside the gas pedal and you rocked your foot on the starter button to goose the throttle while the engine is cranking. It started every time.

I owned a 54 3100 in high school. Here is a beautiful 3600 for sale with starter pedal and 235 6 cylinder engine. 54 was a beauty with the big chrome grille and deluxe cab side windows.

https://classics.autotrader.com/classic-cars-for-sale/chevrolet-3600-for-sale

 

[Greg Bockelman]

What does that have to do with the mixture?

I quickly move the mixture full on and full off. Like a pump of the accelerator in a car.

Nice 5-window, BTW. Not a Chevy fan but I do appreciate nice things.

 

[MooneyDriver78]

The title of the thread is about INJECTED engines, so your carburetor techniques aren’t helpful.

 

[Jim K]

What does that have to do with the mixture?

Nice 5-window, BTW. Not a Chevy fan but I do appreciate nice things.

I think what he's saying is that he's hot-starting his injected engine at ICO, which is what I do. If it doesn't start after a reasonable amount of time, he's quickly opening and closing the mixture to cause the injection system to squirt a little fuel in, similar to what you'd do with the throttle on a carbureted engine to give it a little shot of gas.

 

[Checkout_my_Six]

yup....the accelerator pump is on a carburetor....not a mixture controlled fuel pump.

 

[robin ardoin]

My T210 has a TSIO-520. I didn't think I would like the Conti as well as the Lyco...but I actually like it better. It is amazingly easy to start, hot or cold! Of course, the starter adapter was overhauled a couple of hundred hours ago...we'll see if my opinion still stands once it has some wear and tear. LOL

 

[William Pete Hodges]

What does that have to do with the mixture?

Nice 5-window, BTW. Not a Chevy fan but I do appreciate nice things.

Gentlemen I apologize. I misinterpret the question and how it related to my previous answer... I got sideracked thinking about carburetors.

When hotstarting a hot fuel injected engine it is assumed to be too rich unless it has been sitting for awhile.

I use nearly the same procedure but I crack open the throttle about double for hot start than for cold. It usually starts right up but if it doesn’t start after a few seconds I goose the mixture once to give it a quick shot of fuel. It fires up every time.

1. Adding more throttle adds more air during cranking to help dissipate the fuel. If you are starting hot, then it is assumed the fuel has boiled out of the cylinder lines and overloaded the intake manifold with too much fuel.
2. Leave the mixture on lean cutoff and use the electric pump to purge the unmetered supply lines and control valve.
3. Cranking should cause the engine to fire quickly as it begins too rich and leans out. But...
4. After a few seconds of cranking it may already be too lean to fire, so goosing the mixture sends a shot of fuel into the manifold to richen it up. Alot like an accelerator pump would do on a carburetor.

I hope this is at least clearer than mud. Hot starting a fuel injected engine is a kinda muddy affair sometimes.

 

[172andyou]

Huh, I just realized I know the steps to start a hot engine / flooded engine. But I don't know *why* a hot start is a flooded engine to begin with? Since I stopped the engine 20 minutes ago by pulling the mix, how is it flooded 20 minutes later when I'm ready to leave? Where did that fuel come from?

 

[William Pete Hodges]

Huh, I just realized I know the steps to start a hot engine / flooded engine. But I don't know *why* a hot start is a flooded engine to begin with? Since I stopped the engine 20 minutes ago by pulling the mix, how is it flooded 20 minutes later when I'm ready to leave? Where did that fuel come from?

That fuel comes from the lines that feed the cylinder ports. When you shut off the fuel it stops pumping fuel into the lines. The fuel stops moving but the lines are still full of relatively cool fuel. After stopping the engine it is still hot, and soaks the fuel lines with engine heat. As the lines heat up the fuel expands and vaporizes. The only place for it to go is into the intake manifold. That's where the richness comes from.

 

[asicer]

As the lines heat up the fuel expands and vaporizes. The only place for it to go is into the intake manifold.

...unless there's a fuel return line in the system.

 

[William Pete Hodges]

...unless there's a fuel return line in the system.

Not on the cylinder lines. The fuel return is on the supply side, not on the distribution side.

 

[flyingcheesehead]

The title of the thread is about INJECTED engines, so your carburetor techniques aren’t helpful.

When has a thread title ever stopped us before?

 

[William Pete Hodges]

The title of the thread is about INJECTED engines, so your carburetor techniques aren’t helpful.

When has a thread title ever stopped us before?

You both are correct. MD78- I did apologize for my departure into carburetors, but having done so might give some pilots a better insight into what is really happening. Not as many people are around today who actually daily operated cars, trucks, and tractors with manual or automatic chokes, manual throttles, and breaker point battery ignitions and 6-volt starting systems. Starting these older systems sometimes required some finesse or rethinking. Everyone who drove them had trouble getting them started at times. It is similar with airplane engines now, as modern cars all have electronic fuel injection that makes starting them relatively easy.

Mechanical fuel injection used in airplanes is much different than electronic fuel injection used in cars, boats and outboard motors. It has quirks that operators must understand to be able to operate them reliably. I hope my explanations have helped some.