Injected O-320 Hot Starts

[Bartman]

Hi all,

Wondering what works best for a hot start with a fuel injected O-320 in a Citabria or Decathlon. I've read people can get a hot engine to start after a blade or two but mine turns for a few seconds before catching.

I prime for about three seconds to clear the lines of any vapor, turn off the pump, leave mixture at cut-off, crack the throttle and hope for the best but it doesn't start right up. What's the tweak for a faster start?

Thanks

 

[Sully]

I prime for about three seconds to clear the lines of any vapor, turn off the pump, leave mixture at cut-off, crack the throttle and hope for the best but it doesn't start right up. What's the tweak for a faster start?

Thanks

Mixture rich, prime until good pressure then pump off, mixture ICO and WOT. When it catches, quickly reverse mixture then throttle.
Basically, flood it. At least you know it isn't starved for fuel.

 

[Klaus M]

Everyone has the best technique but, the fuel injected engines that are using the new electronic magnetos need a lot less technique.
The Surefly uses the battery to start and the spark is much stronger.
From their website:

SureFly perfectly controls timing at TDC below 400 rpm, which, combined with longer spark dwell and the option to use wider-gapped spark plugs, makes starting a breeze, greatly minimizing wear and tear on high-performance starters and electrical systems.

Aircraft Electronic Ignition | SureFly

Replace your old aircraft magneto with an electronic ignition from SureFly. Save fuel and reduce maintenance costs.

www.surefly.net

 

[Bartman]

Mixture rich, prime until good pressure then pump off, mixture ICO and WOT. When it catches, quickly reverse mixture then throttle.
Basically, flood it. At least you know it isn't starved for fuel.

that's basically what I'm doing except I'm cracking the throttle, you're suggesting throttle open. I'll give it a try, thanks

 

[Bartman]

Everyone has the best technique but, the fuel injected engines that are using the new electronic magnetos need a lot less technique.
The Surefly uses the battery to start and the spark is much stronger.
From their website:

Aircraft Electronic Ignition | SureFly

Replace your old aircraft magneto with an electronic ignition from SureFly. Save fuel and reduce maintenance costs.

www.surefly.net

I've got stock mags, not quite ready to spend the money to improve hot starts but good to know it's an option. thanks

 

[Bob Turner]

There is a "Koontz" technique floating around that is said to work.

Here is my hot start: throttle cracked, mixture cutoff. Boost pump on, then very quickly blip it with the mixture. In maybe an inch, then immediately back to cutoff. Boost pump off.

Throttle wide open, mixture cutoff, crank. Ten blades later it starts. There has to be a better way.

 

[Mtrask77]

Mine starts hot a little better If I give it more than 3 seconds of prime. It’s more like 4+ seconds. Then, mixture cutoff, throttle cracked, hit starter, then mixture slowly forward at the first hint of light off. Usually ten blades or less before it starts.

 

[vupilot]

No prime, leave throttle where I shut it down, (1000 rpm) Just hit the starter and increase mixture when it fires. Usually spins 4 revolutions then fires. I sometimes open the oil door when its a really hot day, while I fuel or use the restroom or chat with the airport bums, that doesnt change how it starts but it will idle less lumpy.

 

[Bartman]

then there's the lumpy idle! I guess that's normal? perfect mag checks but the idle when it's hot sounds like a dragster from the front seat.

 

[Bob Turner]

My mechanic buddy swears by vu's technique above. I have not been able to make it work.

Yes, all AEIO engines seem to have that funny idle when hot.

 

[Derek Lawless]

No prime, leave throttle where I shut it down, (1000 rpm) Just hit the starter and increase mixture when it fires. Usually spins 4 revolutions then fires. I sometimes open the oil door when it’s a really hot day, while I fuel or use the restroom or chat with the airport bums, that doesnt change how it starts but it will idle less lumpy.

This does work. Works on continentals like the io550k’s too (Cirrus) and lyco 390’s. This was just about the only way to start my Cardinal RG warm.

 

[Skylarktc]

When I try VU’s technique, it always fires right away. But for the life of me, whether I feed the mixture in fast or slow, I can’t keep it running. So I switched to priming for 3 seconds when hot. That works well for me. But also key, is hitting the starter as soon as I’m done priming. No waiting or you just end up flooded.

 

[Ioneater]

Mixture rich, prime until good pressure then pump off, mixture ICO and WOT. When it catches, quickly reverse mixture then throttle.
Basically, flood it. At least you know it isn't starved for fuel.

That’s the technique I was suggested to use on my recent x-country in the heat and it worked like a charm every time. 3-4 blades and it was alive and kicking.

 

[vupilot]

then there's the lumpy idle! I guess that's normal? perfect mag checks but the idle when it's hot sounds like a dragster from the front seat.

Yeah, normal in all the IO- Decathlon/Pitts I've been in on a hot summer day with a quick stop such as a fuel stop. The RV guys complain a lot about it too, but I have yet to fly an injected RV.
If it pops like a small backfire its probably too lean, try a click or two richer on your idle mix thumbwheel on your RSA-5. You can also look into changing the spring in your fuel spider. The firmer spring can increase the pressure coming to the spider slightly which increases the boiling point of the fuel. If it's just lumpy like it misses a little it's all probably set just right. When I bought this Decathlon the idle mix was too lean

 

[vupilot]

When I try VU’s technique, it always fires right away. But for the life of me, whether I feed the mixture in fast or slow, I can’t keep it running. So I switched to priming for 3 seconds when hot. That works well for me. But also key, is hitting the starter as soon as I’m done priming. No waiting or you just end up flooded.

That happens to me too sometimes, usually when it's been more than 30-45 minutes since shutdown and the engine has heat-soaked, peaked and started to cool. A quick 1 sec of prime and it fires back up and stays going. My guess is you can try one click richer on your fuel servo idle thumb screw and see if it changes that behavior. When mine was set leaner it did that almost all the time. But then again other people claim it to be from too much fuel at once and if you crank and move the mixture in slowly and stop moving the mixture when the engine fires it will catch without dying.

 

[Bob Turner]

So today I tried what I thought was the Koontz method - throttle wide open, mixture rich, prime 4 seconds. Mixture cutoff, throttle barely cracked.
Supposed to start on second or third blade.
Not for me.
Back to my old technique, and fired on the tenth blade.
Still seeking a way for less battery drain and starter strain - and to keep my anxiety level low.

 

[Mtrask77]

I’ve only had a hot start go on the 2nd blade one time and I’m not sure what the secret sauce was. I may have run the boost pump a couple seconds longer than usual. I have since not been able to duplicate it. I just have faith that it will start to cough at 10-12 blades and I can run the mixture forward.

 

[Bartman]

I haven’t flown in a few weeks but I have been wanting to try throttle at about 1000 RPM, mixture where it would be leaned for taxi, and a two or three second shot of prime. Probably not flying today either so maybe someone will have a chance to try it before I can.

 

[bcone1381]

The principal to hot starting a Bendix style FI engine is to get a combustable mixture into the cylinders. So whatever technique you choose, understand what state the mixture is before you start. Then keep this up at every failed attempt. (Think "Its Too rich...too lean...it popped so ts getting leaner but its still too rich.")

The mixture in the cylinder should sweep thru a combustable fuel-air ratio, from one side to the other so that it starts when its right. Like those who prime for 4 seconds then start with the throttle wide open...they are flooding it and letting it sweep thru to lean. It sweeps faster thru the possible ratio's because the throttle is wide open. It will sweep with the throttle set at 1100 rpm but it takes longer to sweep through the spectrum.

(Reference Post #8) Those who are not priming but just starting with the throttle set at 1100rpm & mixture ICO are also sweeping across the fuel-air ratios. You see, shile you re-fuel the heat cooks fuel in the lines and fuel drips out the injectors. You can hear the fuel pop and gurgle. This makes the mixture richen up while it sits. So when they start, The mixture is already rich and leaving it at ICO it sweeps across the spectrum.

I do what Post 8 does. If I fail to start I keep trying so Im sure its to lean. By now the engine driven fuel pump has pressurized the fuel system so before I do a start attempt I prime it without using the fuel pump. I can just move the mixture from ICO to rich and back to ICO for a small shot of prime the try again.

As soon as it starts I find that moving the mixture to 50% is appropriate. Once it starts running smooth I know the vapor is out of the lines.

 

[Mtrask77]

No prime, leave throttle where I shut it down, (1000 rpm) Just hit the starter and increase mixture when it fires. Usually spins 4 revolutions then fires. I sometimes open the oil door when its a really hot day, while I fuel or use the restroom or chat with the airport bums, that doesnt change how it starts but it will idle less lumpy.

I tried this technique this morning after a quick fuel stop. Worked as advertised! I will keep trying this to see if it is consistent for my plane.

I tried it earlier in the morning after it sat for an hour and a half and it wasn’t as successful. It wanted some prime. It may have started after more revolutions, but I didn’t want to run the battery down on an untried technique in front of the fly-in breakfast crowd, lol.