For the Aztec drivers.... Starting hot engines

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Cmercado

Pre-takeoff checklist
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Jan 16, 2012
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San Juan, Puerto Rico
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Charlie M
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TJIG
Guys,

Doing my multi training in the Aztruck..... Very honest and ruged bird..But I am having issues starting the engines when hot..... Any tricks from the Aztec guys?

Thanks
Charlie
 
Well, from the single engine guys, start with the mixture off, fuel pump on, crank until it fires then advance the mixture some. Do again twice.
 
Sac Arrow said:
Well, from the single engine guys, start with the mixture off, fuel pump on, crank until it fires then advance the mixture some. Do again twice.
Click to expand...

And if his Aztec has Lycomings with fuel injection, cranking them with the fuel pump on is not likely going to hot start them reliably.
 
The Apache with O-360s I fly is a bear to start hot. I treat it like fuel injected hit start....crack the throttle, leave mixture at idle cut of, crank and add mixture once she fire.
 
Well, after 1,000 hours flying the Aztec, this is what I do with 99% reliability of starting the first time. If you don't believe me, ask Danos. Or ask the DPE who did my multi rating who owned a 135 operating entirely Aztecs, had 9,000 hours of Aztec time, and recommended this method. :)

- Throttle full forward
- Fuel pump on (leave it on!)
- Mixture to full rich for about 2 seconds, then back to idle cut-off
- Crank until catches. Mixture about 1/2 forward, then full rich as it catches fully while reducing throttle to idle.

The last part is the hardest to describe in words, but you should get the hang of it after a few tries. Leaving the electric fuel pump on keeps fuel pressurized to the servo, and seems to aid in starting significantly. If you go full rich too quickly after cranking, the engine will stall.

This method works on every other injected Lycoming I've tried it on.
 
Ted,
Do you use this procedure for all hot starts? Also, define a hot start; how long after the engine has been shut down do you consider a restart a hot start?
 
tmyers said:
Ted,
Do you use this procedure for all hot starts? Also, define a hot start; how long after the engine has been shut down do you consider a restart a hot start?
Click to expand...

Depends on OAT, but up to 2 hours in the summer.
 
Ted DuPuis said:
Well, after 1,000 hours flying the Aztec, this is what I do with 99% reliability of starting the first time. If you don't believe me, ask Danos. Or ask the DPE who did my multi rating who owned a 135 operating entirely Aztecs, had 9,000 hours of Aztec time, and recommended this method. :)

- Throttle full forward
- Fuel pump on (leave it on!)
- Mixture to full rich for about 2 seconds, then back to idle cut-off
- Crank until catches. Mixture about 1/2 forward, then full rich as it catches fully while reducing throttle to idle.

The last part is the hardest to describe in words, but you should get the hang of it after a few tries. Leaving the electric fuel pump on keeps fuel pressurized to the servo, and seems to aid in starting significantly. If you go full rich too quickly after cranking, the engine will stall.

This method works on every other injected Lycoming I've tried it on.
Click to expand...

I have been thinking about this for 2 hours, and I think you might be right. With the mixture to cut off, turning the fuel pump on will not allow fuel into the cylinders until you move the mixture control. :idea:

I have an Air Flow Performance (experimental only) injection system on my IO- 540. It has a bypass system to move hot fuel ( firewall forward) back into the left tank. After 30 seconds it fires right up with your procedure, but I was taught to leave the fuel pump off.

I may need to try this!

You can teach an old dog new tricks. ;)
 
I learned new words during my years with an Azwreck.
 
Ted DuPuis said:
Well, after 1,000 hours flying the Aztec, this is what I do with 99% reliability of starting the first time. If you don't believe me, ask Danos. Or ask the DPE who did my multi rating who owned a 135 operating entirely Aztecs, had 9,000 hours of Aztec time, and recommended this method. :)

- Throttle full forward
- Fuel pump on (leave it on!)
- Mixture to full rich for about 2 seconds, then back to idle cut-off
- Crank until catches. Mixture about 1/2 forward, then full rich as it catches fully while reducing throttle to idle.

The last part is the hardest to describe in words, but you should get the hang of it after a few tries. Leaving the electric fuel pump on keeps fuel pressurized to the servo, and seems to aid in starting significantly. If you go full rich too quickly after cranking, the engine will stall.

This method works on every other injected Lycoming I've tried it on.
Click to expand...

That is the way I had to hot start the C172 with the 180 HP LYC. The last step is tricky with the timing.
 
tmyers said:
Ted,
Do you use this procedure for all hot starts? Also, define a hot start; how long after the engine has been shut down do you consider a restart a hot start?
Click to expand...

I use this for all hot starts on injected Lycomings, yes.

The time after depends, but typically anything from right after shutdown until 2ish hours counts. When in doubt, this method should also work for a cold start, especially a "warm" cold start.
 
Geico266 said:
I have been thinking about this for 2 hours, and I think you might be right. With the mixture to cut off, turning the fuel pump on will not allow fuel into the cylinders until you move the mixture control. :idea:

I have an Air Flow Performance (experimental only) injection system on my IO- 540. It has a bypass system to move hot fuel ( firewall forward) back into the left tank. After 30 seconds it fires right up with your procedure, but I was taught to leave the fuel pump off.

I may need to try this!

You can teach an old dog new tricks. ;)
Click to expand...

I've never worked with the Air Flow Performance system, as you might imagine, so I can't speak to it. But it works very well with the Precision systems that Lycoming uses.

On Navajo engines (at least the ones I flew), this can let extra fuel into the engines, but not enough to matter so long as you aren't sitting around for an extended period without cranking.
 
At the risk of a thread hijack, I have to share my 99.9% reliable method for hot starting the IO-360 on our Cardinal:

Just before you shut down, run the rpm up to 1200 and pull the mixture.

Go about your business. If you come back to the airplane within an hour or so, do your preflight.

Climb in the cockpit. DON'T TOUCH THE FUEL PUMP SWITCH, THROTTLE OR MIXTURE!!

Do your pre-start cockpit checks.

When ready to start: JUST TURN THE KEY!!! DON'T TOUCH THE FUEL PUMP SWITCH, THROTTLE OR MIXTURE!!

The prop will begin to spin. DON'T TOUCH THE FUEL PUMP SWITCH, THROTTLE OR MIXTURE!!

The engine will fire a cylinder. KEEP IT TURNING, BEGIN TO SLOWLLLLLLY EASE IN THE MIXTURE.

The engine will start! :goofy: :yes:


(hat tip: Cardinal Flyers Online)
 
LDJones said:
The Apache with O-360s I fly is a bear to start hot. I treat it like fuel injected hit start....crack the throttle, leave mixture at idle cut of, crank and add mixture once she fire.
Click to expand...
you have something else wrong, maybe mags or plugs. The carb'd engines should be a cakewalk to start.
 
JimNtexas said:
At the risk of a thread hijack, I have to share my 99.9% reliable method for hot starting the IO-360 on our Cardinal:

Just before you shut down, run the rpm up to 1200 and pull the mixture.

Go about your business. If you come back to the airplane within an hour or so, do your preflight.

Climb in the cockpit. DON'T TOUCH THE FUEL PUMP SWITCH, THROTTLE OR MIXTURE!!

Do your pre-start cockpit checks.

When ready to start: JUST TURN THE KEY!!! DON'T TOUCH THE FUEL PUMP SWITCH, THROTTLE OR MIXTURE!!

The prop will begin to spin. DON'T TOUCH THE FUEL PUMP SWITCH, THROTTLE OR MIXTURE!!

The engine will fire a cylinder. KEEP IT TURNING, BEGIN TO SLOWLLLLLLY EASE IN THE MIXTURE.

The engine will start! :goofy: :yes:


(hat tip: Cardinal Flyers Online)
Click to expand...

I've tried that, no joy. :no:
 
JimNtexas said:
At the risk of a thread hijack, I have to share my 99.9% reliable method for hot starting the IO-360 on our Cardinal:

Just before you shut down, run the rpm up to 1200 and pull the mixture.

Go about your business. If you come back to the airplane within an hour or so, do your preflight.

Climb in the cockpit. DON'T TOUCH THE FUEL PUMP SWITCH, THROTTLE OR MIXTURE!!

Do your pre-start cockpit checks.

When ready to start: JUST TURN THE KEY!!! DON'T TOUCH THE FUEL PUMP SWITCH, THROTTLE OR MIXTURE!!

The prop will begin to spin. DON'T TOUCH THE FUEL PUMP SWITCH, THROTTLE OR MIXTURE!!

The engine will fire a cylinder. KEEP IT TURNING, BEGIN TO SLOWLLLLLLY EASE IN THE MIXTURE.

The engine will start! :goofy: :yes:


(hat tip: Cardinal Flyers Online)
Click to expand...

Yeah, I've tried that method and that's also the one they typically recommend on Navajos. My observation is that it works very well on some aircraft and very poorly on others. So it's not a bad one to keep in your bag of tricks. Mine has always worked for me in every injected Lycoming. It's even worked on the 310's IO-520s a few times when the normal hot start procedure for it doesn't work.
 
I have had good success with the hot start procedure in my POH, IO-360, throttle 1/2", mixture idle cutoff, pump on, ease mixture slowly toward rich after it fires. It takes right at 10 seconds of cranking to start but it does. I have never liked the 10 seconds of cranking, so I will try your method and see if it starts any better.
 
Guys,

I tried to hot start the aztruck today with the usual procedure..... Brand new skytec starter and it worked great!!!!! Probably that was it.....
 
There are a lot of things that contribute to starting. The SkyTec starters (guessing it was an NL?) crank the engines over way faster than the factory Prestolite starters, which does help hot starting (and cold starting).

That's one of the reasons why I recommend faster-cranking starters like the SkyTec units.
 
Last edited:
tmyers said:
I have had good success with the hot start procedure in my POH, IO-360, throttle 1/2", mixture idle cutoff, pump on, ease mixture slowly toward rich after it fires. It takes right at 10 seconds of cranking to start but it does. I have never liked the 10 seconds of cranking, so I will try your method and see if it starts any better.
Click to expand...

That extra cranking is what bothers me too. :yes:
 
Ted DuPuis said:
Well, after 1,000 hours flying the Aztec, this is what I do with 99% reliability of starting the first time. If you don't believe me, ask Danos. Or ask the DPE who did my multi rating who owned a 135 operating entirely Aztecs, had 9,000 hours of Aztec time, and recommended this method. :)

- Throttle full forward
- Fuel pump on (leave it on!)
- Mixture to full rich for about 2 seconds, then back to idle cut-off
- Crank until catches. Mixture about 1/2 forward, then full rich as it catches fully while reducing throttle to idle.

The last part is the hardest to describe in words, but you should get the hang of it after a few tries. Leaving the electric fuel pump on keeps fuel pressurized to the servo, and seems to aid in starting significantly. If you go full rich too quickly after cranking, the engine will stall.

This method works on every other injected Lycoming I've tried it on.
Click to expand...
I have a Saratoga turbo and yep, this method works like he says - 99% of the time.
 
Cmercado said:
Guys,

Doing my multi training in the Aztruck..... Very honest and ruged bird..But I am having issues starting the engines when hot..... Any tricks from the Aztec guys?

Thanks
Charlie
Click to expand...

Full throttle, mixture rich, flip fuel pump on, when the needle climbs to full pressure count until 5 then off. Mixture open 1/4", 3/4 throttle. Mags hot, crank, add mixture to lean idle position on the first chuff and reduce throttle as it catches.
 
Ted DuPuis said:
There are a lot of things that contribute to starting. The SkyTec starters (guessing it was an NL?) crank the engines over way faster than the factory Prestolite starters, which does help hot starting (and cold starting).

That's one of the reasons why I recommend faster-cranking starters like the SkyTec units.
Click to expand...

Yes it was an NL... OAT 85 degrees... It worked great..
 
I've found an interesting hot start method shown to me just last year by an guy so old he used to lie down to fly and shift his hips to turn . . . .

this is for Lycs - its weird. I've never heard anyone mention it ever - but by golly - it works on my IO-540 . . .

Throttle 1/2 open - not 1/2" Half open.
Mixture idle cutoff.
Fuel pump on.
Count to 12, maybe 15. [He was a character]
Push the mixture up - see any movement on the pressure needle?
No - pull it back - count to 5. Push it up again.
See fuel pressure- ok - pump off -
Mixture back to idle cutoff.

Turn the key. Chuff Chuff Chuff - release Start

And I'll be damned if the engine does not start almost every single time -

You still need a fast hand since you push up the mixture to about 2/3 whilst pulling the throttle back but that darn engine seems to start every time.

I've never heard of a procedure like that before - but it seems to fill the fuel line to the servo with fuel instead of vapor - and then as you play with the mixture you get fuel into the system all the way . . . which is why a hot start is a pita in the first place . . .
 
Here's the deal, engines need fuel to start, a lot of it, more than most people suspect. The main issue most people have with hot starting injected engines is that they never run enough fuel with the electric pump to purge the boiled dry injector lines with fresh fuel so the engine will start so they have to crank and crank until the mechanical pump finally gets fuel to the cylinders, then it fires.
 
Btw guys,

What velocities are you using for a short field landing on final? I am flying a normally aspirated Aztec C.
 
Check the manual for what it recommends. My method might not be in the book.
 
Cmercado said:
Yes it was an NL... OAT 85 degrees... It worked great..
Click to expand...

The NLs seem to be a big help with injected Lycomings. The Navajo I flew with them would always start unless you really screwed it up. The Navajo with Prestolite starters was not so good.
 
As an old Apache driver, airplane owner, shade tree mechanic, let me comment.
(oh, and as my wife frequently points out "a legend in my own mind")
The O-320/360 series engines are among the most reliable engines in the fleet - if not the most reliable, period.
Most of these engines have 5000 hours or more on the basic accessories.
The engine may have fresh cylinders, etc. and show low time since OH but still start poorly.
There are two main causes for this.
First is (which is really the second most common problem, not first) the carburetor throttle shaft. The shaft has been rotated uncountable millions of times over the years and the shaft holes in the throttle body are wallowed out. They leak air around the shaft and the butterfly is eccentric in the throat. Either send the carb out for a rebuild, or have your mechanic install new throttle shaft bushings. It is a kit he can get with the proper size drill and the bushings. Makes a ton of difference in how smoothly the engine operates. Replacing the accelerator pump with new is mandatory.

Second (which is really the first in importance) is the magneto. Most (meaning 99.9%) plane owners are too cheap to keep the mags in proper condition. If you have slick mags, throw them away (personal opinion shared by every old mechanic I know) They do not seem to have the hot spark needed at low cranking speeds.
You want a Bendix mag. You want the mag overhauled. Either send it out, or have an 'old' mechanic rebuild it. If the impulse coupling has more than about 300 hours on it, throw that away also and put on a new coupling.
Suspect the drive gear of being worn if it is a 5000 hour magneto and just replace it.
Check the shaft bushings by seeing if there is any sideways slop in the shaft (a real killer for starting) If so new bushings are needed.
Time the magneto properly (some mechanics cannot seem to do this simple task properly). Make the mechanic do it with you watching. To know what you are seeing buy the book on magnetos from Sacramento Sky Ranch.
And lastly - wires (gotta be good) and plugs. If it is a high time engine consider that the plugs might be fouling during starting attempts. If so replace the plugs fired by the left magneto with fine wire platinum plugs. Yeah, expensive but cheaper than being at a dark airport with a run down battery trying to get back home..

The group has already pointed out the advantages of a high speed starter.
Let me also comment that an RG battery makes a huge difference in cranking speed.

Now, Fat Albert has all if the above items I mentioned done and NL starters. The fat boy starts reliably within just a few blades, cold or hot - has not failed even once in the 13 years I have owned him.
Amazing, considering he still has the aluminum starter cables the factory installed in 1956.
 
comanchepilot said:
I've found an interesting hot start method shown to me just last year by an guy so old he used to lie down to fly and shift his hips to turn
Click to expand...
that's not anything special. Everyone's "cookbook" is really the same thing. Flood the intake with fuel, then open the throttle while cranking to move a lot of air. The extra air will purge the excess fuel until it reaches a mixture that happy to light off.
 
JHW said:
that's not anything special. Everyone's "cookbook" is really the same thing. Flood the intake with fuel, then open the throttle while cranking to move a lot of air. The extra air will purge the excess fuel until it reaches a mixture that happy to light off.
Click to expand...

True, but the one thing you get with leaving the electric fuel pump on is more pressure to the servo. This will turn whatever fuel vapor was there into liquid fuel (theoretically) and the servo also tends to like more fuel pressure.

On some Lycomings (and more Continentals) you see a fuel return that means if you leave the fuel pump on it will cycle fuel back to the tanks, circulating cool fuel. I've never really found this to matter much, but supposedly the big turbo Contis like it, and I've got pretty close to zero time flying those.
 
Ted DuPuis said:
On some Lycomings (and more Continentals) you see a fuel return that means if you leave the fuel pump on it will cycle fuel back to the tanks, circulating cool fuel. I've never really found this to matter much, but supposedly the big turbo Contis like it, and I've got pretty close to zero time flying those.
Click to expand...

It makes a big difference on the Ovation - A true hot start is difficult to impossible unless I circulate cool fuel through the system for a minute or so (full throttle, idle mixture, pump on, wait). After that, it's much easier but still probably takes 15 blades.
 
What method are you using on the Ovation fot hot starts?
 
Ted DuPuis said:
What method are you using on the Ovation fot hot starts?
Click to expand...

Mostly what's in the book, although the book says to do 5 seconds on high boost or 15 on low boost rather than the 30-60 seconds that got me out of trouble on a hot day in Wyoming on the way home...

Then, throttle idle, mixture rich, and crank. Not what I'm seeing people use here, but it's in the book that way. I'll have to try your method next time, but I don't expect that to happen for a while - It's probably too cold here for anything in the next few months to really be a "hot" start.
 
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