IO-520 Hot Starts?

AirBaker

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AirBaker
As I have yet to master the hot start on my V35, I wanted to know if anyone has tips that have helped them out. I've been told a number of theories, and all seem to work sometimes. :)

From what I've read online, looks like running the fuel pump with the mixture at full lean for a minute then initiating the cold start procedure is what I'll try next. I've been averaging the 3rd shot each time with a hot start.
 
AirBaker said:
As I have yet to master the hot start on my V35, I wanted to know if anyone has tips that have helped them out. I've been told a number of theories, and all seem to work sometimes. :)

From what I've read online, looks like running the fuel pump with the mixture at full lean for a minute then initiating the cold start procedure is what I'll try next. I've been averaging the 3rd shot each time with a hot start.

The procedure you mention simply cools the engine fuel pump and fuel servo (mixture control unit) so that the fuel doesn't boil in them when you try to start. I'm not certain that one minute is enough if the engine is really hot and has been sitting long enough for the heat to soak into the fuel pump and servo (that takes a few minutes itself). I wouldn't use the "cold start" procedure after running the boost pump as the engine doesn't need anywhere near as rich a mixture to start when hot. Assuming you have a two speed boost pump (hi/low boost), you might find it helpful to switch on the low boost as you start to crank (mixture rich, throttle set for 1200 RPM). Also I'd make sure the throttle was fully closed in addition to putting the mixture in idle cutoff when you run hi boost to cool the system.

I'm told the Slick-Start electronic "shower of sparks" unit can improve hot starting drastically, but I haven't had to resort to that.
 
On the IO 520 (Centurion) I've been using a "crossover" start. Throttle and mix wide open, 5 sec of prime (there's some fuel pooled in the intake manifold). Close mix, WOT, Crank. As the C/S rolls, the mix will start rich and then lean as there is no more fuel being added. When it catches, open the mixture to full rich. You may actually have to hit prime as fuel is still vaporizing in the spider 'cause it's too darn hot. Works on about six or seven blades.
 
You'd think that all of the engines would start the same way, but they each seem to have a mind of their own. Once you find the secret with yours you'll be all set. Until then, you might want to have a power cart standing by.

Here's what works for me on a hot start:

Mixture - Idle cutoff
Throttle - Full forward
Boost Pump - On high for 30 seconds or longer then off

Mixture - Full rich
Throttle - Cracked
Boost Pump - just a shot - about a one count - then off

Start cranking and be ready to hit the boost pump once it fires.

YMMV.

Chip
 
so true Chip... hey someone explain this one (not necessarily a hot start thing but a cranky engine concept):
TIO 540s on an Aztec. NEITHER will start if you don't follow the handwritten procedure to the letter AND it includes, "the instant you first hear it fire, you MUST release the starter switch" because if you continue to crank it one second beyond that point, it will NOT catch. I didn't beleive it til I intentionally contravened the 'rule' and learned the hard way. (sure looks stupid taxiing on one engine in an aztec)
 
Let'sgoflying! said:
so true Chip... hey someone explain this one (not necessarily a hot start thing but a cranky engine concept):
TIO 540s on an Aztec. NEITHER will start if you don't follow the handwritten procedure to the letter AND it includes, "the instant you first hear it fire, you MUST release the starter switch" because if you continue to crank it one second beyond that point, it will NOT catch. I didn't beleive it til I intentionally contravened the 'rule' and learned the hard way. (sure looks stupid taxiing on one engine in an aztec)

I've started engines that seemed to exhibit the same behavior (starts better if you stop cranking earlier), but since it made no sense, I never actually adopted this as a procedure except out of desparation.
 
bbchien said:
On the IO 520 (Centurion) I've been using a "crossover" start. Throttle and mix wide open, 5 sec of prime (there's some fuel pooled in the intake manifold). Close mix, WOT, Crank. As the C/S rolls, the mix will start rich and then lean as there is no more fuel being added. When it catches, open the mixture to full rich.

I've never been too fond of this method (flood,crank w/o fuel), but must admit that I have used it more than once. The downsides are the potential for an intake fire (probably needs a leaky intake valve for that), and cylinder wall washdown. Both issues are exacerbated if you go beyond the 5 second prime "to be sure it's flooded" as I've seen some do.

bbchien said:
You may actually have to hit prime as fuel is still vaporizing in the spider 'cause it's too darn hot. Works on about six or seven blades.

You raise a good point. Starting the engine involves both getting it to fire and keeping it running. In the Baron, I've found that continuous low boost generally takes care of the latter when hot.
 
AirBaker said:
As I have yet to master the hot start on my V35, I wanted to know if anyone has tips that have helped them out. I've been told a number of theories, and all seem to work sometimes. :)

From what I've read online, looks like running the fuel pump with the mixture at full lean for a minute then initiating the cold start procedure is what I'll try next. I've been averaging the 3rd shot each time with a hot start.

My system FWIW on all fuel injected recips for hot start.

Throttle Full
Mixture Rich
Boost pump on just until fuel flow registers then off.
Throttle 1/8
Mixture 1/4
Crank
Feed mix to half as engine catches
Bring back throttle as engine smooths

:dance:
 
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