Warm IO-360 Start: Why have I never heard of this trick?

wilkersk

wilkersk

Pattern Altitude
Joined
May 21, 2015
Messages
2,445
Location
Puget Sound
Display Name
Display name:
KennyW
So today, I did something I rarely do. I flooded a fuel injected aircraft on a warm start after refueling. I followed the checklist for warm start, no go. I turned everything off and got out just to confirm; yep, a couple of fresh drops of 100LL under the cowl. Now what?

I let it sit for a minute and tried again, using the check list. No good. I call the FBO. The owner, a really nice guy, says he'll be right over to give me a hand.

He walks on over and proceeds to show me a trick I do not ever recall seeing or hearing about. He says that warm fuel injected engines will vapor lock easily, and the only way to fix it is to relief the pressure on the manifold. He pushes both throttle and mixture control full-in and tells me to count to five. He then pulls the mixture to idle cut-off and tells me to crank the engine. The damn thing catches first blade!

Why have I never seen this before? Has anyone else been taught this?
 
In counting to 5, is that running the pump for those 5 seconds?
If so, that is the only way I can get my I0520 to start hot. Pull throttle, push mixture quick when it catches though.
 
If the pump is running, that's pushing the fuel vapor out of the fuel lines, and it's a conventional hot start solution for airplanes vulnerable to vapor lock (e.g., Cardinal RG).

The "relieving pressure" thing doesn't make a whole lot of sense. If the fuel manifold is pressurized, it will make no difference to cranking with the mixture at idle cutoff.
 
If I recall correctly it requires 3 hands to start a hot TSIO-520! :D There are several techniques that seem to work, some better on some engines, some not so good. I used to leave the throttle at about 1000 RPM for shutdown, then push the mixture up and crank, use primer to keep it running until it smoothed out. :D I also used what you described, it seemed to depend on the airplane, how hot it was and how long it had sat since shutdown. :dunno:
 
N747JB said:
If I recall correctly it requires 3 hands to start a hot TSIO-520! :D There are several techniques that seem to work, some better on some engines, some not so good. I used to leave the throttle at about 1000 RPM for shutdown, then push the mixture up and crank, use primer to keep it running until it smoothed out. :D I also used what you described, it seemed to depend on the airplane, how hot it was and how long it had sat since shutdown. :dunno:
Click to expand...
Three hands and a prayer, and then it only works if there is nobody behind you at the fuel pump. If there is, you just have to get out and push it out of the way or it will never start. But as soon as you move it and nobody is watching, it will start right up (if you use the correct procedure, which includes 30 seconds of boost pump at WOT and Mixture at cutoff. Then do a normal start with just a few seconds of boost pump first.
 
MAKG1 said:
The "relieving pressure" thing doesn't make a whole lot of sense. If the fuel manifold is pressurized, it will make no difference to cranking with the mixture at idle cutoff.
Click to expand...

It makes sense to me as the boiling air bubbles creates pressure in the injector manifold. So since the fuel that was pressurized behind the filter is now evaporated, it creates a vacuum behind the insulator right? So opening the fuel flow not only cools the area by flooding it with fuel, and I guess the high pressure would help push the cooler fuel into the manifold.

I've never heard of that technique, but it's pretty neat depending...

Depending on how long it was between you stopping your action and the owner starting his action. I wonder if the fuel had enough time to stop boiling and released the vapor pressure?
 
Last edited:
Archammer said:
It makes sense to me as the boiling air bubbles creates pressure in the injector manifold. So since the fuel that was pressurized behind the filter is now evaporated, it creates a vacuum behind the insulator right? So opening the fuel flow not only cools the area, and I guess the high pressure would help suck the cooler fuel into the manifold.

I've never heard of that technique, but it's pretty neat depending...

Depending on how long it was between you stopping your action and the owner starting his action. I wonder if the fuel had enough time to stop boiling and released the vapor pressure?
Click to expand...

The injectors are not used during cranking. It's done at idle cutoff.
 
Looks like it's a good practice! Because the injection plumbing is on the cool side (top) of that particular engine, it's great when moving, but when static the heat rising causes vapor locking frequently. Here's the POH details for a Saratoga with an Lyc. IO-540 on a hot start:

Saratoga PA-32-300:

Intentionally flood the engine. This runs cool fuel through the plumbing and "breaks" the vapor lock.

a) Full rich
b) Wide open throttle
c) Fuel pump on, watch fuel flow gauge (5-7 sec)
d) When gauge registers flow, wait 3-5 seconds then red knob to ICO and pump off.
Crank engine with red knob still at ICO and with throttle wide open at first. Gradually close throttle (at a rate that will take you about 10 seconds to close the throttle) and it should start up at some point.

When engine catches, do several things more or less simultaneously:

a) release ignition key
b) throttle to idle to avoid over-revving
c) mixture full rich.
Click to expand...
 
Last edited:
Situations like this make me wonder why aviation hasn't picked up on using stand alone engine management systems to make things easier.
 
Yup, boost pump on, mixture ICO, throttle all the way in, then mixture rich and throttle idle once it catches.

Always worked for me on 360s, 520s and 550s.
 
Maciej said:
Situations like this make me wonder why aviation hasn't picked up on using stand alone engine management systems to make things easier.
Click to expand...

Yeah, were still using incandescent nav lights, one baby step at a time or the FAA will start crying :lol:
 
Last edited:
After two years of my IO 360 its little different...no pump...open the throttle full for 20 sec to relieve pressure and back to idle...crank and then slowly move mixture to full and it kicks every time...doing it by the book had me more than frustrated...this works as well...then again a little voodoo also works...
 
I do this starting an io-540.
1. Mixture idle
2. Full throttle
3. Some people will run the full pump here to blow the line clear, but just for a few seconds. Then shut pump.
4. Turn the key
5. As engine starts to catch decrease throttle while increasing mixture. Doing these at the same time is the hard part.

Sent from my SM-G920V using Tapatalk
 
Hot start, some would intentionally flood the engine and then complete the flooded engine start. Basically throttle up, mixture idle cutoff, advance the mixture when it fires.
 
The main difference in cold and hot starting procedures are whether prime is applied or not. Continental IO engines, at least the ones I'm familiar with, are started full rich, vs. idle cutoff for Lycomings due to the different fuel delivery systems.
 
Wish I had a IO-360 to vapor lock. Sure would make my Sport climb better...:yes::yes:

Great trick, makes sense to me.
icon14.gif
 
I used to run the fuel pump for 1 full minute on hot fuel injected engines prior to start. Idle cut off, Throttle wide, pump on to flush the heat soaked fuel lines with cold/cooler fuel. Then give it a shot of prime/mixture then back to ICO and crank...
 
Lycomings and continentals have different FI systems, different techniques are required, OP works for Lycomings


Sent from my iPhone using Tapatalk
 
It doesn't take three hands, but you have to be prepared to get your hand over to the throttle once it catches before you go to full power on the thing.
 
flyingron said:
It doesn't take three hands, but you have to be prepared to get your hand over to the throttle once it catches before you go to full power on the thing.
Click to expand...

Yup, best hot start on our IO-360 is full throttle mixture at idle cutoff. As soon as it fires put the mixture in and yank the throttle out. Just imagine the backlash if the average person had to monkey with their car engines like this.
 
Bill Jennings said:
Yup, best hot start on our IO-360 is full throttle mixture at idle cutoff. As soon as it fires put the mixture in and yank the throttle out. Just imagine the backlash if the average person had to monkey with their car engines like this.
Click to expand...

You had to monkey like that with cars for many years.

Never drove a carb' car, I see.

You just call the mixture a "choke."
 
A poster above mentioned dripping fuel in the cowl. My thoughts turn toward starting safety in preventing engine fires, the kind you do not want. What things do you guys do to mitigate that risk?

I think I can recall only once having trouble warm starting my Lyc IO-360
 
MAKG1 said:
You had to monkey like that with cars for many years.

Never drove a carb' car, I see.

You just call the mixture a "choke."
Click to expand...

Yeah, but cars weren't that hard even with carbs. Cold start pump the throttle to the floor once to set the choke then crank. Warm start part throttle and then crank. Once in a really great while it would flood, just hold the throttle to the floor and crank until she fires.

But today, just turn the key, and that was my reference. Most folks today (especially younger people) only know to turn the key.
 
Bill Jennings said:
Yeah, but cars weren't that hard even with carbs. Cold start pump the throttle to the floor once to set the choke then crank. Warm start part throttle and then crank. Once in a really great while it would flood, just hold the throttle to the floor and crank until she fires.

But today, just turn the key, and that was my reference. Most folks today (especially younger people) only know to turn the key.
Click to expand...

You've never used a manual choke….

Those were common into the 70s. It's essentially a backwards mixture knob and is used similarly at start and sometimes cold idle.
 
You must log in or register to reply here.
Back
Top