Hot starting a Silver Hawk FI

[Kent Ashton]

Chaps, my friend with a Cozy is having a hard time hot-starting his O-360, magnetos, & Silver Hawk FI. Here's what I told him but I am not a FI guy (I have an Ellison!) so check me on this advice:

After shutdown, the fuel spider is still pressurized and will dribble fuel into the cylinders. That excess fuel must be cleared by cranking the engine with throttle wide open and mixture cutoff for XXX number of turns (how many?).

If the throttle is cracked open prior to clearing the excess fuel, it will re-flood the cylinders and he may need to start over.

While cranking to clearing the excess fuel, keep the impulse mag on. If a cylinder fires he will know he has cleared back to a stoichiometric mixture and can enrichen the mixture (but how much?)

After a hot engine has sat for a while (how long?), the excess fuel will be evaporated by the hot cylinders and a relatively normal cold start procedure may be used (or a modified cold start procedure?)

I told him shutting off the high pressure boost pump won't help because mixture cutoff shuts down fuel to the injectors. Yes?

He tells me his engine starts well when cold.

TIA
Kent Ashton
Cozy Mk IV

 

[lr172]

Not pressurized. Fuel in lines from spider boils and this pushes fuel to cyls making them rich, but lines are now empty. After some period of time fuel evaporates from cyl intake area and now it is not rich and lines still empty. We don't clear the fuel in a separate step, we just use it in the procedure.

I do NOT recommend full throttle start attempts and they are NOT required. It is just too easy to let the plane get away from you if distracted.

throttle 1/4"
mixture rich
boost pump on for 1 second (refills lines and insures cyl is over rich)
mixture ICO
crank until it kicks over, then mixture rich

If it kicks over then dies, just hit the start button again and it will go. On the rare occasion it doesn't go, just repeat above steps and try again. Remember the 20 second use/60 second rest duty cycle for the starter.

Larry

 

[rmarshall234]

I’m not going to comment on technique but I’ve never been a fan of hot starts from an “ over rich “ condition. I know that’s the common practice but often results in belching black smoke and one cylinder coming to life at a time. I don’t like it. I’ve never owned a FI aircraft engine ( and prefer not to because of the hot start problem ) but as a mechanic I’ve started lots of different ones and have been successful when the owner was not on several occasions. I prefer to get the fuel out of there and then start from a too lean condition. But then, I fly behind an Ellison too.

 

[lr172]

I’m not going to comment on technique but I’ve never been a fan of hot starts from an “ over rich “ condition. I know that’s the common practice but often results in belching black smoke and one cylinder coming to life at a time. I don’t like it. I’ve never owned a FI aircraft engine ( and prefer not to because of the hot start problem ) but as a mechanic I’ve started lots of different ones and have been successful when the owner was not on several occasions. I prefer to get the fuel out of there and then start from a too lean condition. But then, I fly behind an Ellison too.

None of this is magic and several ways to attack the problem. But there is a problem that has to be overcome. When the fuel boils it empties the lines and dumps it all into the intake chamber. It will stay there for a while, but will eventually evaporate. Not sure it is any better to crank away and blow the fuel out in raw form vs the black stuff that comes out when it kicks over too rich. Because of this problem, it will NEVER hot start like your Toyota; Just the nature of the system. The flooding + cranking ICO approach is common mostly because it can easilly be taught to those that don't understand the what and why of internal combustion and it is repeatably successful for the unskilled.

 

[Carl Froehlich]

Builders learned to build a plane. Pilots learned to fly. Hot starts is just another thing to learn.

I disagree that injected engines have a hot start problem. I do many fuel stops of 20 min or less. What I do for such hot, summer starts:
- Mixture stays at Cut Out
- Boost pump stays off
- Both ignitions on (dual pMags, if you have standard mags turn on only the impulse mag)
- Throttle between half and full open, less if the stop is longer)
- Crank

The engine normally fires after a couple of blades. There is plenty of time to bring the throttle back then move the mixture to my normal taxi position.

Carl

 

[pilotkms]

What Carl says +

I do what Carl says and no problem. 6years and at least 500 hot starts. I do a lot of short flites for lunch. Of course I’m no mechanic so I don’t over-think it.

 

[eaglen92ce]

Plus one on Carl's technique. I do it SLIGHTLY differently but it is basically what Carl recommends. NO BOOST PUMP on hot engine. Mixture ICA. Start cranking and advance the throttle fairly quickly. Engine will fire usually around half throttle, when it fires mixture rich, boost on to keep it running, throttle back to idle. This has worked great for me on three different airplanes I have owned and I recently showed it to a friend with a Long EZ with Airflow Performance FI and it works well for him also. Also a Mooney friend has used it with great success as well. It can be a little bit of a hand full (coordination exercise) to get the mixture forward, throttle back and boost on (if needed). After a few times though it will become second nature.

Basically the hot engine is already RICH. Adding boost fuel makes it worse. What the engine wants is a good starting mixture, air is what it needs and what opening the throttle plate provides. You will find that the throttle position where it fires will be fairly consistent. One you figure that out, maybe you could just start with the throttle there. For me I like to move into it from a lower throttle position, you don't want to start with it above the optimum position and then be moving the throttle even more open.

Give it a try!

 

[newt]

If the mixture is at ICO, running the boost pump won't add more fuel to the system, it'll just pressurize the supply-side of the fuel servo, just like the engine-driven pump does after the engine fires.

So whether you start with the pump on, or start with it off and turn it on when the engine catches, won't make any difference.

(unless your fuel servo is worn out and allowing fuel to bleed through a lean cutoff mixture setting)


- mark

 

[rmarshall234]

The most interesting hot start procedure I’ve encountered to date, is the hot start of an old “E-Series” Bonanza ( my other airplane ) with a pressure carburetor and wobble pump. Done properly, it’s a thing of beauty because it requires very precise timing. After shutdown with a pressure carb, fuel pools in the intake runners and then vaporizes. This fuel vapor is important and is utilized for the hot start. Normal start procedures apply….throttle cracked, mixture rich, but instead of applying fuel pressure with the wobble pump as is normally done….you have the pump handle extended and your arm is poised and ready for action. As soon as you crank the engine it fires off immediately on that residual fuel charge (vapor) but will die without the timely “ wobbling “ of the fuel pump. The timing needs to be spot on or you are faced with a likely flooding situation on the next start. It was a challenge to learn but very satisfying to do it right. (Said I wasn’t going to discuss (debate) procedures but this is different and informative IMO)

 

[Low Pass]

Builders learned to build a plane. Pilots learned to fly. Hot starts is just another thing to learn.

I disagree that injected engines have a hot start problem. I do many fuel stops of 20 min or less. What I do for such hot, summer starts:
- Mixture stays at Cut Out
- Boost pump stays off
- Both ignitions on (dual pMags, if you have standard mags turn on only the impulse mag)
- Throttle between half and full open, less if the stop is longer)
- Crank

The engine normally fires after a couple of blades. There is plenty of time to bring the throttle back then move the mixture to my normal taxi position.

Carl

I've had two Silverhawk systems on separate engines. Recommend the procedure above. But NOT more than 15-20% open throttle at start. I've never needed more throttle. No need for incurring the risk.