Hot engine starts

skidoo

skidoo

Line Up and Wait
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skidoo
My POH says to prime the engine when it is cold. It also says to omit the priming if it is not cold. So, after a short stop with engine shut down, I go to re-start omitting the priming. No start! So, I prime... No start. I spend perhaps 5 to 8 minutes trying to start with prime, without prime, etc... Finally, somehow I get it started.

So, I am wondering, if the procedure is to pull the mixture to shut down the engine, thereby removing fuel from the cylinders, then how does it get the fuel to start if I don't prime before re-starting?

Any tips for more consistent starts with a hot engine? Mine is a Lyc TIO-540 with turbo.
 
Hot starts in a turbo or other HP engine can be a real pain.

Every engine has a slightly different technique, and that is best learned from someone who knows your airplane/ engine.
 
dmccormack said:
Every engine has a slightly different technique, and that is best learned from someone who knows your airplane/ engine.
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Yep.

I have an O320-D3G that is carburated.

I find the easiest hot start is no prime, throttle full open, mix at idle cut off and then crank. The second it starts to catch pull the trottle and push the mixture to full rich.
 
dmccormack said:
Hot starts in a turbo or other HP engine can be a real pain.
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Not if you know a few very simple techniques.

For a injected Continental (with a fuel return line; make sure yours has one), it really couldn't be simpler (I think AOPA had a good primer on this subject a while ago, but I can't find it). Mixture ICO, a bit of throttle, and run the boost pump for a minute or so. Then mixture full, boost pump off, and crank right away.

The main reasons hot starts are difficult is because of fuel that vaporizes almost instantly in the hot fuel lines. Circulate some cold fuel to cool them down and get rid of the vapor, and you're virtually guaranteed an engine start. Then, if you get to know your specific engine, you might be able to find ways that work for your engine and are easier.

-Felix
 
You may have a marginal mag but if not, I'll share my 1000+ hours of experience with TIO540s in Commanders 115s. The problem time always seemed to be between 15 minutes to about 45 minutes after shutdown. A shutdown and restart within a few minutes never seemed to be much of an issue with no prime, just turn the key and go. If I let it sit for an hour, then a normal cold start would do it. In that interim time, I always thought it was probably boiling off enough fuel to vapor lock. The only 100% fool proof procedure I found was that, if I was starting it in that vapor lock zone, I'd just go ahead and flood the crap out of it which would force all the air out of the lines and then do a flooded engine start. I know people will say that I was running the risk of an engine fire but in thousands of starts in every kind of conditions from normal temps to 120 F desert starts in the SW US, it worked every time.

Contis are different due to the fuel return line. You can run fuel through the lines and over the pump to cool it without flooding the engine. I used the procedure described above worked pretty well in my Columbia 400. I'd just run the "Vapor Suppress" for at least a minute and then it would fire right up with a normal start.
 
PittsDriver said:
The only 100% fool proof procedure I found was that, if I was starting it in that vapor lock zone, I'd just go ahead and flood the crap out of it which would force all the air out of the lines and then do a flooded engine start. I know people will say that I was running the risk of an engine fire but in thousands of starts in every kind of conditions from normal temps to 120 F desert starts in the SW US, it worked every time.
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Good technique, too. I know someone who does this very reliably with this IO550...
 
i regularly used the flood it method with the GTSIO-520H on the 421 and it was always reliable.
 
I was using the flood technique on the IO-540 when hot until I had an instructor show me that it would crank quicker with full rich and throttle cracked. It cranks a little differently now that servo and engine have been overhauled, needing a hit on the boost pump occasionally after it fires. So you just have to find what works for you on your engine.
 
A local shop owner whose typical business day includes numerous hot starts (mostly big-bore continentals) says he has almost 30 years of first-hand experience and at least 100 years of advice on the subject.

He follows the standard cold-start procedure on each hot start, but starts opening the throttle after the first crank and continues until the mixture is correct for starting. A few additional blades are sometimes required, but the monkey motion with the mixture and throttle is eliminated.

After watching him use the procedure without fail for a number of years, I have switched from the flooded method to his simpler method with excellent success.
 
I went through a few months of difficult cranking just thinking that I wasn't getting the process quite right myself and it ultimately turned out that I had a marginal impulse coupling in the mag. Once replaced, it would fire on the first blade nearly always.

This whole process of how we shut down our fuel injected engines and restart them has always been a bit of a puzzlement to me. Take for example my current AEIO-540 in the Pitts - I shut it down by pulling the mixture to idle cut off with the throttle at idle and then turn off the mags. If I go to start it in the next few minutes, all I have to do is turn the key and it cranks without touching anything else - it's still at idle cut off and the throttle is still at idle. I haven't touched a thing but now it runs when a few minutes ago, that was the configuration that killed it. I've been told that after I shut it down, some fuel is boiled out of the injector lines into the cylinders - enough to crank it with the shower of sparks that get's shot to it when I turn the key. It still seems pretty much like magic though.

I almost always crank any engine with the throttle set to idle. It's like fingernails on a chalkboard to me when I hear someone crank up a cold engine and let it rev like crazy.
 
wabower said:
A local shop owner whose typical business day includes numerous hot starts (mostly big-bore continentals) says he has almost 30 years of first-hand experience and at least 100 years of advice on the subject.

He follows the standard cold-start procedure on each hot start, but starts opening the throttle after the first crank and continues until the mixture is correct for starting. A few additional blades are sometimes required, but the monkey motion with the mixture and throttle is eliminated.

After watching him use the procedure without fail for a number of years, I have switched from the flooded method to his simpler method with excellent success.
Click to expand...

That's what I do. Works.
 
On my injected Lycomings my standard procedure is throttle full open, crank until it starts firing, mixture halfway until it catches, throttle back to idle. Works great, although I haven't tried that technique in the summer yet. Flooding it is another technique that works, and is what I used to do, but this method is easier on the starters.

On the Mooney, hot start technique (injected angle valve 360) that worked every time was throttle forward, mixture back, crank until it sputtered, and then mixture full rich throttle back. Each plane does have its own trick. I view this as an anti-theft feature. :D
 
Fuel pump is your friend. Use him.
 
Thanks everyone. Great input! I'll make note of some of these techniques and try them when the time comes again...
 
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