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RV14 IO390 difficult to start

Adriaan Kleyn

I'm New Here
I struggle to start my RV14 IO390 cold or hot. I can't find a procedure that works consistently every time. With my Cessna 182 with a Lycoming IO 540 it is easy,when cold - throttle full forward, mixture full rich ,prime till you get a positive fuel flow, mixture fully lean, throttle 1/4 inch and crank. It will start immediately. When cold - throttle 1/4 inch, mixture fully lean, crank and catch with the mixture when it fires. It work every time and I have never had a flooded engine. With my IO390 it is very different story, since I've had a flooded engine several times as well as a flat battery. I have tried several different techniques but doesn't get consistent results. I need some advice.
 
I'm certainly no expert , but I find just the opposite with my I0-390 (RV-14A0 and the 0-540 in what use to be our RV-10. Only start issue I've had so far (knock on wood) is trying to re-start for fuel after shutting down for the night and not opening the fuel valve.
I do the same procedure as you but I only advance the mixture after it begins to fire and I only move it forward slowly.
 
Sounds similar to my RV-10 story, IO540

It came from the overhaul shop with retard mags, and no Slickstart -- took about 18 months of dead batteries to figure it out --- installed Slickstart and problem went away.

Ron
 
I think you are overpriming. I have found it takes very little prime, less than 2 seconds of pump with the throttle only cracked about a quarter.

Try that.

Vic
 
With the first (RV-14A) prototype, we learned after some initial struggles, that the Andair fuel pump is a very high volume flow pump.

Any RV model equipped with the Andair pump will require a change in priming technique from what people have always used / learned.

First start of the day in warmer weather I put throttle and mixture full fwd and run the pump for about 1 second (in mid summer temps even that is sometimes too long). Then set the throttle to about 1/4" open and crank. It should start right up.
In (our pacific north west) cold weather I double the time. In real cold climates you might have to do 3 seconds, but I doubt it will ever require more than that.

For hot starts I use the mixture sweep method with the throttle open about 1/2"

Side tip...... If you do get a start but the engine is stumbling badly Usually because it is heavily rich / over primed, immediately pull the mixture to cut-off. When the engine operation begins to smooth out, push the mixture back in to about the 2/3rds fwd point and adjust the throttle for proper idle.
 
I know your pain

We had the same issues. Here is how we do it.(Lycoming instructions) Cold start: all controls fully forward. Pump on 3 seconds. Mixture at idle cutoff, fully aft. Throttle open 1/2 inch. Advance mixture slowly while turning over engine. Fully advance mixture when engine fires and adjust idle. Hot start- Throttle FULLY forward. Mixture forward, prime 2 seconds. Mixture fully aft to idle/cutoff. LEAVE THROTTLE AT FULLY FORWARD. Turn engine over and DO NOT push in mixture until engine fires. Push mixture forward and QUICKLY retard THROTTLE. Resist temptation to advance the mixture knob until engine fires! Also, just turn engine over only 5-7 seconds at a time. Let system rest about 30 seconds between tries. Our personal final solution is to install Pmags.
 
Vic, what do you do with the mixture after priming? Do you leave it fully rich or do you catch it when it fires.

The mixture is in idle cutoff for starting and I move it forward as it catches. Seems to work well so far.

As Scott, mentioned, the pump seems to flow much more fuel than we have been used to. I'm amazed at how little priming is needed.

Vic
 
A cranking engine will fire only when the in-cylinder fuel-air ratio is within a narrow range. It's near impossible to figure out a perfect "sweet spot" setting for all conditions and all airplanes.

So, a successful start procedure finds the sweet spot by sweeping fuel-air ratio through a range of mixtures while cranking, moving either from rich to lean, or from lean to rich. At some point in the sweep, one or more cylinders pass through the sweet spot, and it fires.

Think about how to sweep the mixture, experiment with the knobs a bit to accomplish a sweep, and you'll arrive at procedure that works for you.

http://www.vansairforce.com/community/showpost.php?p=1181708&postcount=18
 
a successful start procedure finds the sweet spot by sweeping fuel-air ratio through a range of mixtures while cranking

This is how I have always thought of it.

So far I have used the Lycoming manual procedures without fail or sweat. One thing not mentioned here so far is their reference to exactly how much to prime in a cold start. They call for priming until the FF reaches 4 gph then pull mixture to ICO.

This seems to me to account for the differences in fuel pump rates or pressures.

I also believe it it important to get the idle mixture set correctly. As Tim Olsen mentioned in one of his threads the idle mixture seems to come set on the rich side from the factory. I found this to be true and on mine, it was very rich.

Starting takes place in the throttle range were this setting accounts for a lot of the fuel flow to the engine. Leaving it too rich could have an adverse effect on starting.
 
I have found the problem, and she starts like magic now,hot or cold. It was strange to me that it only starts when you leaves the key and not while the starter is engaged ( if she starts ). On the ignition there are to ground positions. The one is for both magneto's and the other one is only for the right magneto. When you engage the starter it grounds the right magneto so that only the left magneto with the impulse fires. The problem was that the ground was on the left magneto so the wrong magneto was grounded when the the starter was engaged. I have swop the ground wire and the problem is solved.
 
With the first (RV-14A) prototype, we learned after some initial struggles, that the Andair fuel pump is a very high volume flow pump.

Any RV model equipped with the Andair pump will require a change in priming technique from what people have always used / learned.

First start of the day in warmer weather I put throttle and mixture full fwd and run the pump for about 1 second

I don't get it: What does the throttle position have to do with priming a F/I engine? What does a fuel injector care whether the butterfly is open or closed while priming?

~Marc
 
I don't get it: What does the throttle position have to do with priming a F/I engine? What does a fuel injector care whether the butterfly is open or closed while priming?

~Marc

Do some reading on the way mechanical fuel injection works.

The throttle arm on the servo / throttle body opens and closes the throttle plate (butterfly) and controls a fuel pressure regulator within the servo that varies the fuel pressure in the fuel line that links to the distribution manifold on the top of the engine.
This variable fuel pressure is what regulates the amount of fuel that flows out of the constant flow injectors.
 
Do some reading on the way mechanical fuel injection works.

The throttle arm on the servo / throttle body opens and closes the throttle plate (butterfly) and controls a fuel pressure regulator within the servo that varies the fuel pressure in the fuel line that links to the distribution manifold on the top of the engine.
This variable fuel pressure is what regulates the amount of fuel that flows out of the constant flow injectors.

I did do some reading Scott, and what I read is pretty specific that AIRFLOW through the servo determines how much fuel is released to the flow divider. If the engine is not running, there is no airflow through the servo. It doesn't matter what position the throttle plate is in.

My RV-10 has an AFP fuel system, which Don says is the same basic system as Bendix.

From the AFP manual: "The FM-series fuel injection system uses the proven principal of mass airflow metering to proportion the fuel flow to the engine.
The FM-series system is a mass airflow device employing a venturi to generate a signal corresponding to the mass airflow..."

So if there is no airflow (as when priming a non-running engine), what difference does it make if the throttle plate is open or closed?

-Marc
 
I'm guessing Scott knows what he is talking about here. The AFP instructions for cold starting that I have indicate to prime with the throttle in for a few seconds and then pull it out to idle before starting. Works well. Not so well when i prime with the throttle out. There is clearly something going on here other than airflow

Erich
 
Lycomings instructions

From the Lycoming page:

https://www.lycoming.com/content/tips-start-your-engine

"Most Lycoming fuel-injected engines are simply primed by turning the fuel boost pump on, opening the mixture briefly to full rich, and cracking the throttle. Any pumping of the throttle is ineffective until the engine begins to fire."

When I start my engine I go mixture rich, throttle cracked (only because I want to start it at idle with some air), fuel pump on and bypass valve in for 5 seconds to prime.

-Marc
 
On a Bendix style servo the throttle arm has a mechanical connection to a control valve.

When the throttle arm moves between idle and WOT, it is changing the position of this valve.

The linkage to this valve is adjusted to change idle mixture (rate of fuel delivery by the injectors).

I never meant to imply that said valve was the only control of fuel delivery.... just that it does have an influence on the amount of delivery.
 
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