Shutdown proceedure for IO520

Aircraft powered airboat discussion.
fladan
Southern Airboat Member
Posts: 21
Joined: Fri Feb 06, 2015 12:41 am
Location: Rockledge Fl

Shutdown proceedure for IO520

Post by fladan » Fri Jun 17, 2016 1:20 am

I would like to know what the proper shut down procedure is for a fuel injected Continental 520. I have a switch for the fuel pump, fuel cut-off and a switch for each mag. I have been told that once I am running, I can turn off the fuel pump so if I remember, I do. The problem I am having is that is just wants to keep on running and sometimes backfires and runs backwards before it stops. I know this can't be good, so I am wondering what I need to do so it STOPS when I want it to.

I have tried shutting off the fuel cut-off switch and wait for it to quit, but it seems to linger on and keeps running. In desperation, I turn off both mags and it still wants to go until it starts to cough or run backwards and I turn the mags back on (and it runs) and then back off. I just can't seem to find the right combination to stop the motor in what I think is in a healthy way every time I want to stop. Any ideals?

User avatar
digginfool
Site Supporter - III
Site Supporter - III
Posts: 2725
Joined: Wed Jun 05, 2013 3:00 pm
Location: South Florida

Re: Shutdown proceedure for IO520

Post by digginfool » Fri Jun 17, 2016 6:12 am

Two things come to mind. First, when you get to where you want to stop, do you let the engine run for a few minutes at idle to let it cool down? Second, are you running avgas? Running mogas will make the engine run hot and can also create the issue you are describing. Apparently, you are running an injected motor but both of these conditions can cause a carbureted motor to Diesel and, you're right, it's not good for the motor. I've no experience with injected AC motors but I would imagine that if the engine is hot enough and there's fuel in the lines it could get enough to Diesel on after you shut off the mags.
“When plunder becomes a way of life for a group of men living together in society, they create for themselves in the course of time a legal system that authorizes it and a moral code that glorifies it” - Bastiat

Dirtman
Site Supporter - IV
Site Supporter - IV
Posts: 297
Joined: Sun Aug 18, 2013 5:08 pm
Location: St.Cloud FL

Re: Shutdown proceedure for IO520

Post by Dirtman » Fri Jun 17, 2016 6:13 am

If the lean out is adjusted properly to cut off the fuel then pulling the cable for the lean out should cut off the fuel and the engine should shut down on its own and then you shut off the mag switches. That is how mine works anyway. Sounds like the cable for the lean out might not be shutting fuel flow off completely. If its possible with the engine ideling move the lean out lever by hand to the completely off position and see if it shuts down any quicker if so just adjust the cable, if not possibly fuel is getting by the lean out and there is a problem in the barrel valve. If you find you have a problem bypassing fuel past the barrel valve, Joey aka Qwikdiesel is in Melbourne and he really knows his stuff on fuel injection systems
Last edited by Dirtman on Fri Jun 17, 2016 10:29 am, edited 1 time in total.
IO520 on a 12"6" Lazer with a 72" Q #20814
Build in progress: 14x7'9" JB w/ GSO540 &80" Razor

terrible ted
Southern Airboat Member
Posts: 2830
Joined: Tue Aug 12, 2008 8:07 pm
Location: orlando

Re: Shutdown proceedure for IO520

Post by terrible ted » Fri Jun 17, 2016 8:08 am

He never mentions the lean out - does it have one?

User avatar
Planeguy
Southern Airboat Member
Posts: 179
Joined: Sun Sep 06, 2015 4:49 pm
Location: OK

Re: Shutdown proceedure for IO520

Post by Planeguy » Fri Jun 17, 2016 8:17 am

I agree with Dirtman and Digginfool, if it is dieseling then you are still getting fuel into the cylinders. Assuming you are using the stock injection system... are you using the mixture cutoff on the fuel servo (throttle body) or a cutoff in the line somewhere? Just killing the pump would still allow some fuel to be pulled to the engine and a remote cutoff could do the same. The best way to shut down would be to tun the pump off and move the mixture control to the cutoff position (again, assuming stock setup) then turn off the mags after engine stops.

Digginfool also had a good point about the heat and fuel type.

schmidtav2
Site Supporter - VII
Site Supporter - VII
Posts: 311
Joined: Thu Aug 02, 2007 8:40 pm
Location: Ft Lauderdale, Fl

Re: Shutdown proceedure for IO520

Post by schmidtav2 » Fri Jun 17, 2016 8:40 am

I use an electric fuel solenoid in the fuel supply line to the manifold valve, the solenoid is powered thru a toggle switch to turn it on/off. Turn it on to allow fuel thru it to the manifold valve and turn it off to stop the fuel to the manifold, the engine will shut off clean with in 2-3 seconds every time.

User avatar
Planeguy
Southern Airboat Member
Posts: 179
Joined: Sun Sep 06, 2015 4:49 pm
Location: OK

Re: Shutdown proceedure for IO520

Post by Planeguy » Fri Jun 17, 2016 10:03 am

Another question would be... are you sure the mags are shutting off? Just because the switch is off doesn't mean they are grounded. They won't fire if they are spinning backwards but if they are sparking and still getting a little fuel it will act like it is dieseling.

fladan
Southern Airboat Member
Posts: 21
Joined: Fri Feb 06, 2015 12:41 am
Location: Rockledge Fl

Re: Shutdown proceedure for IO520

Post by fladan » Fri Jun 17, 2016 10:55 am

First off, thanks for the response! To clarify, it is fuel injected so no carb and I do have an electric fuel solenoid in the fuel line before the manifold. I do use 87 octane pump gas and have 8.5 pistons. The top end is fresh with new pistons/rings/valves and 53 hours on the clock. The injection system was just overhauled and the fuel solenoid is new. Pretty much a new motor.

I have tried letting it run for a few minutes before shutting down, but still have the same run-on problems. Like schmidtav2 said, I thought once I shut off the fuel solenoid, it would stop within a few seconds. As far as it getting hot, I just ran the motor for three minutes in the yard to load it back up on the trailer and have the same symptoms as if I ran for 30 minutes in the swamp. I have done a mag check recently by shutting one off at a time and the rpm's dropped a few hundred each time so I'm assuming they are okay. Oh, new switches, gauges and wiring throughout.

Is there an adjustment on the injections system to make it leaner or richer? Maybe it's to rich?

never enuff
Southern Airboat Member
Posts: 104
Joined: Wed Mar 25, 2009 8:31 pm
Location: Ft.Pierce

Re: Shutdown proceedure for IO520

Post by never enuff » Fri Jun 17, 2016 11:07 am

There is your problem too low of a octane.

User avatar
digginfool
Site Supporter - III
Site Supporter - III
Posts: 2725
Joined: Wed Jun 05, 2013 3:00 pm
Location: South Florida

Re: Shutdown proceedure for IO520

Post by digginfool » Fri Jun 17, 2016 11:12 am

never enuff wrote:There is your problem too low of a octane.
If you're not going to run avgas (which you should), at least run the highest octane fuel you can find. 87 is disaster waiting to happen. AC motors were designed for the slow burn of high octane fuel. Low octane fuel burns hot and fast. Plus, with the high heat of air cooled engines, the low octane can, and most likely will, cause detonation which will destroy your motor.
“When plunder becomes a way of life for a group of men living together in society, they create for themselves in the course of time a legal system that authorizes it and a moral code that glorifies it” - Bastiat

pax1ton
Southern Airboat Member
Posts: 231
Joined: Tue Mar 06, 2007 8:31 pm
Location: Nebraska

Re: Shutdown proceedure for IO520

Post by pax1ton » Fri Jun 17, 2016 11:27 am

Proper shutdown, pull rich lean cable to full lean ,after engine quits both mag switches to off( grounded)
if engine tries to run on or diesel after going to full lean , its an adjustment problem at the barrel valve,(fuel not getting completely shut off)
on a side note fuel octane would have nothing to do with the problem, its just not shutting the fuel supply off completely

User avatar
HAMMERHEAD
Southern Airboat Member
Posts: 2269
Joined: Mon Jan 11, 2010 7:58 pm
Location: GAINESVILLE

Re: Shutdown proceedure for IO520

Post by HAMMERHEAD » Fri Jun 17, 2016 11:58 am

Fuel would absolutely make the engine run backwards! The shut down procedure for an airplane isn't always practical for an airboat. For example you are idling up to other boats or a dock and you want to stop close. You can't pull a lean cable and wait for the engine to shut down. Wether it be proper procedure or not I have always shut the motors down with the mag switches. Not to mention the likely hood of forgetting to shut the mag switches off when shutting down with fuel. Just my two cents.

User avatar
digginfool
Site Supporter - III
Site Supporter - III
Posts: 2725
Joined: Wed Jun 05, 2013 3:00 pm
Location: South Florida

Re: Shutdown proceedure for IO520

Post by digginfool » Fri Jun 17, 2016 12:10 pm

pax1ton wrote:Proper shutdown, pull rich lean cable to full lean ,after engine quits both mag switches to off( grounded)
if engine tries to run on or diesel after going to full lean , its an adjustment problem at the barrel valve,(fuel not getting completely shut off)
on a side note fuel octane would have nothing to do with the problem, its just not shutting the fuel supply off completely
In the case of an injected motor, octane rating may not have anything to do with the Dieseling issue but everything else is true; if you're not running avgas, you should run the highest octane you can find.
“When plunder becomes a way of life for a group of men living together in society, they create for themselves in the course of time a legal system that authorizes it and a moral code that glorifies it” - Bastiat

fladan
Southern Airboat Member
Posts: 21
Joined: Fri Feb 06, 2015 12:41 am
Location: Rockledge Fl

Re: Shutdown proceedure for IO520

Post by fladan » Fri Jun 17, 2016 3:42 pm

Thank you for all the input. My first move will be to try 93 octane and if that doesn't fix the problem then I'll try avgas. I appreciate all the help!

pax1ton
Southern Airboat Member
Posts: 231
Joined: Tue Mar 06, 2007 8:31 pm
Location: Nebraska

Re: Shutdown proceedure for IO520

Post by pax1ton » Fri Jun 17, 2016 8:33 pm

HAMMERHEAD wrote:Fuel would absolutely make the engine run backwards! The shut down procedure for an airplane isn't always practical for an airboat. For example you are idling up to other boats or a dock and you want to stop close. You can't pull a lean cable and wait for the engine to shut down. Wether it be proper procedure or not I have always shut the motors down with the mag switches. Not to mention the likely hood of forgetting to shut the mag switches off when shutting down with fuel. Just my two cents.
Fair enough response, The only thing that should be added ,when shutting down with the mag switch and not the rich lean handle,
one must remember that theres burnable fuel left in the cylinders ,and if a mag switch or wiring would go bad, it could leave ya with a hot mag .
any movement of the prop could cause the engine to fire.

User avatar
Planeguy
Southern Airboat Member
Posts: 179
Joined: Sun Sep 06, 2015 4:49 pm
Location: OK

Re: Shutdown proceedure for IO520

Post by Planeguy » Sat Jun 18, 2016 7:25 am

HAMMERHEAD wrote:... The shut down procedure for an airplane isn't always practical for an airboat. For example you are idling up to other boats or a dock and you want to stop close. You can't pull a lean cable and wait for the engine to shut down. ...
I am not really an airboater yet but can that extra half second at idle really be that big of a deal? It seems to be it wouldn't be hard to get use to.

User avatar
Deano
Site Supporter - V
Site Supporter - V
Posts: 4549
Joined: Thu Jan 06, 2005 11:16 am
Location: Inverness, FL

Re: Shutdown proceedure for IO520

Post by Deano » Sat Jun 18, 2016 8:27 am

If that process really only took a half a second it may be easier to 'adjust to' as you say, but realistically shutting down in that fashion does not happen that quickly in most cases.

Consider if you will, that when you shut down your airplane, you have ground friction that has already stopped your forward momentum (you can idle without moving . . . not so with a boat), and you are usually well removed from people and any other obstacles that possibly contribute to committing a terrible OOPS. :shock:

In many cases, when docking an airboat there may be currents and/or wind to deal with and unlike your momentum, steering control stops at the same time the prop stops moving air over the rudders. Beyond that there may very well be people in a much closer proximity where a turning prop is far less desirable.

Using the mags to shut down is not only more time effective by allowing prolonged maneuverability and control when docking, but can very well be a safer alternative in many common scenarios with an airboat that you simply don't encounter with an airplane.
"The suppression of uncomfortable ideas may be common in religion and politics,
but it is not the path to knowledge; it has no place in the endeavor of science."
- Carl Sagan

User avatar
Planeguy
Southern Airboat Member
Posts: 179
Joined: Sun Sep 06, 2015 4:49 pm
Location: OK

Re: Shutdown proceedure for IO520

Post by Planeguy » Sat Jun 18, 2016 4:10 pm

Deano wrote:If that process really only took a half a second it may be easier to 'adjust to' as you say, but realistically shutting down in that fashion does not happen that quickly in most cases.

Consider if you will, that when you shut down your airplane, you have ground friction that has already stopped your forward momentum (you can idle without moving . . . not so with a boat), and you are usually well removed from people and any other obstacles that possibly contribute to committing a terrible OOPS. :shock:

In many cases, when docking an airboat there may be currents and/or wind to deal with and unlike your momentum, steering control stops at the same time the prop stops moving air over the rudders. Beyond that there may very well be people in a much closer proximity where a turning prop is far less desirable.

Using the mags to shut down is not only more time effective by allowing prolonged maneuverability and control when docking, but can very well be a safer alternative in many common scenarios with an airboat that you simply don't encounter with an airplane.
It sounds to me like you have about as much airplane and airport experience as I have airboat experience. Consider, if you will, not all airplanes have brakes and most will roll on concrete (even on grass) if simply left to idle without chalking a wheel or setting a brake. I have flown many aircraft that would not sit still at idle. None of the six aircraft I fly here will sit still at idle on concrete. Only about half of them will sit still on the grass if it hasn't rained in a while (idle ranges between 500 and 700 rpm, one Cessna will idle at 400) I once saw an airplane start to roll after few minutes at idle. The pilot started it to go fly then decided to leave it running while he went into the office "for a minute".

On the flip side, I do have quite a bit of boating experience and outboards are easier than airplanes. Current and wind are the same for all boats. Outboards just give you reverse to use if you come in too fast or miss your target but I have been seeing some talk and pictures about airboats with brakes, powered anchors and trolling motors which would be of great use in tight areas.

Most of the time, if an aircraft engine will not shut off immediately when the mixture is pulled, there is something wrong with the setup. I see a lot of posts about the mixture arm tied to full rich. That is a case where I would expect the engine to run for a bit when the fuel is turned off. If you want to talk safety, lets explore how a properly set up engine without fuel cannot run while simply turning off a mag switch may or may not kill the engine due to a bad switch, bad wire or any other bad connection to the ground without any warning. Imagine the OOPS :shock: that would cause. As pointed out by others above, even without spark, an engine getting fuel can still possibly run some (even backwards). Which brings up another safety concern pointed out by others above. Bump a prop with fuel left in the engine and risk a nasty surprise there too if mags decide they aren't grounded. I have been flying and playing around with piston aircraft engines for 23 years. The only one that failed to turn off immediately for me using mixture was when a cable broke when I pulled it to shut down and I had been telling the owner for months it was going to fail. I have replaced several ignition switches and ground wires (p-leads) over the years. Most failed without warning. Only replaced one mixture cable to date and it gave me lots of warning.

Just my 2 cents but it seems like if a person wants to use an aircraft engine then it should be operated like one if they want the benefits of it. Treating it like a car engine is just inviting problems.

User avatar
Deano
Site Supporter - V
Site Supporter - V
Posts: 4549
Joined: Thu Jan 06, 2005 11:16 am
Location: Inverness, FL

Re: Shutdown proceedure for IO520

Post by Deano » Sat Jun 18, 2016 8:27 pm

Planeguy wrote: I am not really an airboater yet but can that extra half second at idle really be that big of a deal? It seems to be it wouldn't be hard to get use to.
After seeing this post, I was only meaning to afford you some insight that you seemed to lack due to inexperience with an airboat, no more, no less. My bad. I was only responding to this single question you asked, not attempting to engage in a debate about the thread's contents.

Until you stated as much, I had no means of knowing that you had quite a bit of outboard experience and had been 'reading about and looking at pictures of airboats with brakes, powered anchors and trolling motors.' You'll have it all figured out in no time. Obviously you are already well versed in shutting down your engine.

Have a nice weekend. :salute:
"The suppression of uncomfortable ideas may be common in religion and politics,
but it is not the path to knowledge; it has no place in the endeavor of science."
- Carl Sagan

User avatar
Planeguy
Southern Airboat Member
Posts: 179
Joined: Sun Sep 06, 2015 4:49 pm
Location: OK

Re: Shutdown proceedure for IO520

Post by Planeguy » Sun Jun 19, 2016 9:59 am

Deano.. Your input is much appreciated. Only by reading posts like yours can I gain the understanding and knowledge I need. There are a few things I can't understand, like why anyone would tie the mixture lever open on an aircraft carb or throttle servo then install a separate shutoff in line and complain it won't shut down immediately when the fuel is shut off. Maybe most complaints are coming from people who have installed automotive carbs on aircraft engines. There is just so much I do not know and that lack of understanding is what prompted the question you responded to. I probably should have phrased my question more along those lines but some of it is just occurring to me as I type this.

User avatar
trailerdon
Site Supporter - IV
Site Supporter - IV
Posts: 313
Joined: Mon Aug 02, 2010 9:24 pm
Location: Port Charlotte, Fl

Re: Shutdown proceedure for IO520

Post by trailerdon » Mon Jun 20, 2016 7:16 am

skip the 93 and go straight to av gas. Problem solved !

fladan
Southern Airboat Member
Posts: 21
Joined: Fri Feb 06, 2015 12:41 am
Location: Rockledge Fl

Re: Shutdown proceedure for IO520

Post by fladan » Wed Jul 20, 2016 12:44 am

I just wanted to bring this thread to a close by reporting that switching to 93 octane I have solved my problem. I have run at least 8 tanks of 93 octane through my motor and is ready to stop now when I am! Thanks for the expertise and input from this site to solving my problem!

Moritz
Southern Airboat Member
Posts: 543
Joined: Tue Mar 07, 2006 9:57 pm
Location: Texas

Re: Shutdown proceedure for IO520

Post by Moritz » Wed Jul 20, 2016 10:33 pm

slow the idle speed down to 500 or less this will help. if the idle is up over a 1000 they want to run on. I have this engine in my plain and always pull the mixture to full lean and engine back to idle and it cut off

titan
Southern Airboat Member
Posts: 183
Joined: Sun May 31, 2009 5:53 pm
Location: Volusia Co.

Re: Shutdown proceedure for IO520

Post by titan » Sat Jan 27, 2018 11:30 pm

What part number, brand, size is the electric fuel solenoid shut off that Schmitt was talking about?

GMAC 76
Site Supporter - V
Site Supporter - V
Posts: 1237
Joined: Sun Jan 04, 2009 11:12 pm
Location: LAKE PLACID FL.... LAKE ISTOKPOGA

Re: Shutdown proceedure for IO520

Post by GMAC 76 » Sun Jan 28, 2018 10:38 am

I honestly and truly love all the guys that start their engines on both mags and use only the mags to shut'em down....it keeps my little mag repair shop busy...lol

Post Reply

Return to “Aircraft Power Only”