Starting a hot Fuel Inj. engine
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Starting a hot Fuel Inj. engine
After doing a fair bit of searching on here and being told a number of different methods to try, I haven't come across a "works every time" method of starting hot fuel injected engines. I will be flying a Continental IO-470 Debonair and have been told by the owner to "tickle the fuel pump when it sounds like dying". Sounds very hit and miss to me!
Any helpful tips that people have discovered that work more often than not when starting a hot continental?
Cheers
Any helpful tips that people have discovered that work more often than not when starting a hot continental?
Cheers
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starting hot Continentals
It's been a long time since I flew Bonanzas and Barons, but I remember their Continental IO-520s being much easier to start when hot than the comparable Lycomings on the Aztec.
Open the throttle just a little, select the mixture to Rich, turn the boost pump on and leave it on until the fuel flow stabilises on the fuel flowmeter, turn the boost pump off, select the mixture to Idle-cutoff. Now you can start the engine, and when it fires, smoothly advance the mixture to Rich. Works every time, whether the engine is hot or cold.
I think your IO-470 will start in a similar fashion.
Open the throttle just a little, select the mixture to Rich, turn the boost pump on and leave it on until the fuel flow stabilises on the fuel flowmeter, turn the boost pump off, select the mixture to Idle-cutoff. Now you can start the engine, and when it fires, smoothly advance the mixture to Rich. Works every time, whether the engine is hot or cold.
I think your IO-470 will start in a similar fashion.
Lots of different techniques out there but this one has never failed me with IO-520s anyway. Mixture Idle Cut off, Throttles Fully open. HP fuel pump on for 30 seconds. Then straight away carry out the cold start procedure. Will get lots of cold fuel through the lines and i've never had a mis-start using said procedure.
I'm sure there will be other techniques, but this one seems less hit and miss.
I'm sure there will be other techniques, but this one seems less hit and miss.
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Well said DD, as you would know about starting hot engines especially the IO540 (Lyc).
I am NO expert, but do have significant time flying both the Lycoming 540 and the Continental 520 engines, I don't mean to preach (especially to those who already know) but to have an understanding of the engine manufacturer will help you with your choice of starting techniques.
The two engines of choice for the 6-8 seat single have traditionally been the
Lycoming IO-540 (and its many variants TSIO etc) and the
Continental IO-520 also with a few mods and derivatives.
Lyc engines have the fuel injection nozzles in such a place that the fuel (vapour) is sprayed directly onto the back of the intake valve. When you prime you get lots of effective fuel (vapour) in the immediate area of the valve and at least one cylinder gets a good shot of fuel.
Therefore over priming floods the engine. When starting you need to take away a lot of the fuel (vapour and liquid) before the best mixture is obtained in the cylinders for the spark to be able to ignite it. In other words the engine seems to crank for a few seconds before it fires. Then reintroduce the fuel with the mixture control.
This is why you start in ICO (idle Cutoff) so no new fuel is introduced which will guarantee a flooded start.
This is also the preferred manufactures start method. ie With the Mixture rich for only a short (3 sec) prime, them Mixture ICO until the engine fires on start.
For a HOT start the engine should NOT be primed. Ie the fuel pump should only be run for a very short time (to pressurise the fuel lines) with the mixture in ICO (no fuel flows to the injectors) as the fuel vapour already present after the shutdown will be sufficient to get a start.
Continental 520 series engines have the injector further away from the intake valve. In this case fuel (vapour) tends to sit back from the valve. When cranking (low suction) only floating vapour in the intake can get into the cylinder and ignite. This is almost opposite to the Lyc engines and means you need lots of fuel to get the engine to fire. The continental engine need mixture rich and really decent prime to get a good start.
HOT starting the conti. engine is done the same as for a cold start but you do have a higher chance of a "Vapour Lock" occurring.
(Vapour locks occur in all of these type of engines, but the Cont. 520/470 seems to be the most common to see it)
Simply a vapour lock is caused when the warm (hot) engine creates a low density of air in the manifold, the suction in the cylinder has trouble moving this low density air containing fuel vapour into the cylinder, and the air that dose make it has a very low effective mixture.
The answer is to prime the engine a bit more, and as the manufacturer recommends you can use the primer during start to boost the fuel/air ratio to achieve a start.
Most Conti. engines exhibiting a vapour lock will start, then die (use up the available prime fuel) so you need to give it a good prime, and then when it starts to die (tickle it) until it is self sustaining.
CAUTION as over priming during start can and WILL cause induction fires (a fire in the induction manifold) or in the engine bay (as the over primed fuel leaks into the engine bay from the manifold drains).
This is why you should NEVER delay a start after fuel pump priming (Always Prime, Clear Prop and Start within a few seconds).
Having said ALL of the above, all engines are slightly individual and while many different methods DO work it is best to use the method given to you by the aircraft/engine manufacturer.
CHADZAT while this question gave me and others a good chance to dribble on for a few pages, the only real question to ask is "Where is the POH, mate"
Have fun the Debo is a very nice thing to fly.
Richo
I am NO expert, but do have significant time flying both the Lycoming 540 and the Continental 520 engines, I don't mean to preach (especially to those who already know) but to have an understanding of the engine manufacturer will help you with your choice of starting techniques.
The two engines of choice for the 6-8 seat single have traditionally been the
Lycoming IO-540 (and its many variants TSIO etc) and the
Continental IO-520 also with a few mods and derivatives.
Lyc engines have the fuel injection nozzles in such a place that the fuel (vapour) is sprayed directly onto the back of the intake valve. When you prime you get lots of effective fuel (vapour) in the immediate area of the valve and at least one cylinder gets a good shot of fuel.
Therefore over priming floods the engine. When starting you need to take away a lot of the fuel (vapour and liquid) before the best mixture is obtained in the cylinders for the spark to be able to ignite it. In other words the engine seems to crank for a few seconds before it fires. Then reintroduce the fuel with the mixture control.
This is why you start in ICO (idle Cutoff) so no new fuel is introduced which will guarantee a flooded start.
This is also the preferred manufactures start method. ie With the Mixture rich for only a short (3 sec) prime, them Mixture ICO until the engine fires on start.
For a HOT start the engine should NOT be primed. Ie the fuel pump should only be run for a very short time (to pressurise the fuel lines) with the mixture in ICO (no fuel flows to the injectors) as the fuel vapour already present after the shutdown will be sufficient to get a start.
Continental 520 series engines have the injector further away from the intake valve. In this case fuel (vapour) tends to sit back from the valve. When cranking (low suction) only floating vapour in the intake can get into the cylinder and ignite. This is almost opposite to the Lyc engines and means you need lots of fuel to get the engine to fire. The continental engine need mixture rich and really decent prime to get a good start.
HOT starting the conti. engine is done the same as for a cold start but you do have a higher chance of a "Vapour Lock" occurring.
(Vapour locks occur in all of these type of engines, but the Cont. 520/470 seems to be the most common to see it)
Simply a vapour lock is caused when the warm (hot) engine creates a low density of air in the manifold, the suction in the cylinder has trouble moving this low density air containing fuel vapour into the cylinder, and the air that dose make it has a very low effective mixture.
The answer is to prime the engine a bit more, and as the manufacturer recommends you can use the primer during start to boost the fuel/air ratio to achieve a start.
Most Conti. engines exhibiting a vapour lock will start, then die (use up the available prime fuel) so you need to give it a good prime, and then when it starts to die (tickle it) until it is self sustaining.
CAUTION as over priming during start can and WILL cause induction fires (a fire in the induction manifold) or in the engine bay (as the over primed fuel leaks into the engine bay from the manifold drains).
This is why you should NEVER delay a start after fuel pump priming (Always Prime, Clear Prop and Start within a few seconds).
Having said ALL of the above, all engines are slightly individual and while many different methods DO work it is best to use the method given to you by the aircraft/engine manufacturer.
CHADZAT while this question gave me and others a good chance to dribble on for a few pages, the only real question to ask is "Where is the POH, mate"
Have fun the Debo is a very nice thing to fly.
Richo
Thread Starter
Thanks Richo (and others) that information is invaluable and in-depth engine characteristics should be taught up to CPL.
POH- On closer inspection
there is a note that says:
"If the engine is hot, place mixture control in IDLE CUT-OFF, switch auxiliary fuel pump to ON for 30 to 60 seconds, then OFF. Return mixture to full rich and continue with cold start procedure."
Might pay to read the notes in future
Being an (almost) newbie CPL these sorts of "informative posts" are invaluable to me as I am sure there are heaps of Ppruners out there that have a heap of this knowledge stored up. In particular the characteristics and facts that go beyond the POH wording.
Keep the discussion going!
Cheers
POH- On closer inspection
there is a note that says:"If the engine is hot, place mixture control in IDLE CUT-OFF, switch auxiliary fuel pump to ON for 30 to 60 seconds, then OFF. Return mixture to full rich and continue with cold start procedure."
Might pay to read the notes in future
Being an (almost) newbie CPL these sorts of "informative posts" are invaluable to me as I am sure there are heaps of Ppruners out there that have a heap of this knowledge stored up. In particular the characteristics and facts that go beyond the POH wording.
Keep the discussion going!
Cheers
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Bent conrod
Somewhere in my office there is a very bent conrod, out of a C310 engine. This engine was primed before the starter was engaged, and the prop only turned about 15 degrees and stopped.
The engine was wrecked. Conrod, piston, crankshaft, crankcase-all unuseable.
One cylinder had been full of fuel.
This engine had a problem with the fuel control unit, but there was also a note in the POH saying not to prime unless the propeller was turning. This applies to Cessna 340's and some C310's.
Read the book!!!
The engine was wrecked. Conrod, piston, crankshaft, crankcase-all unuseable.
One cylinder had been full of fuel.
This engine had a problem with the fuel control unit, but there was also a note in the POH saying not to prime unless the propeller was turning. This applies to Cessna 340's and some C310's.
Read the book!!!
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Hit and miss? maybe not
Your bosses tip of tickling the boost pump does have a basis in sound science.
As you probably know or do now from the previous threads. When a hot fuel injected engine sits it is often possible for the fuel contained within the 1/8 stainless steel fuel lines from the flow divider to the fuel injector nozzles to vapourise or boil off. You then have nothing but basically air in those lines.
Lycoming and TCM have somewhat different fuel metering systems and if you have the time, Aircraft Fuel Metering Systems by Aviation Maintenance Foundation Inc. is worth a read and explains the various systems well. You often find this range of publications in the various pilot shops and they are quite cheap. i digress.
The idea of selecting ICO (idle cut off) and full throttle and boost pump on, allows cooler fuel to be pumped into the body of the flow divider but it doesn't go to the injector lines due ICO being selected. From here it returns to the fuel tanks via the vapour vent line attached to the flow divider. The 60 seconds allows enough time for the cooler fuel to replace the small amount of fuel in the divider and remove some of the heat in the body of the divider.
So when you do finally introduce fuel to the injector lines (by coming out of ICO) it is hopefully cool enough to last sufficient time in the lines to get you started before it to vapourises.
Or maybe not. Here is where your bosses tip comes in. The engine fires but then starts to die, you've just struck some air in the line and a quick flick of the boost pump sends a rush all be it small rush of fuel up the injector line and hopefully you catch it before it dies.
Hope this gives you some insight, but please don't take my scribblings as a definitive description of this small part of the system. Grab a tech manual sometime. You might also find the principals of the air bleed injector different to what many would tell you.
Best of Luck
M
As you probably know or do now from the previous threads. When a hot fuel injected engine sits it is often possible for the fuel contained within the 1/8 stainless steel fuel lines from the flow divider to the fuel injector nozzles to vapourise or boil off. You then have nothing but basically air in those lines.
Lycoming and TCM have somewhat different fuel metering systems and if you have the time, Aircraft Fuel Metering Systems by Aviation Maintenance Foundation Inc. is worth a read and explains the various systems well. You often find this range of publications in the various pilot shops and they are quite cheap. i digress.
The idea of selecting ICO (idle cut off) and full throttle and boost pump on, allows cooler fuel to be pumped into the body of the flow divider but it doesn't go to the injector lines due ICO being selected. From here it returns to the fuel tanks via the vapour vent line attached to the flow divider. The 60 seconds allows enough time for the cooler fuel to replace the small amount of fuel in the divider and remove some of the heat in the body of the divider.
So when you do finally introduce fuel to the injector lines (by coming out of ICO) it is hopefully cool enough to last sufficient time in the lines to get you started before it to vapourises.
Or maybe not. Here is where your bosses tip comes in. The engine fires but then starts to die, you've just struck some air in the line and a quick flick of the boost pump sends a rush all be it small rush of fuel up the injector line and hopefully you catch it before it dies.
Hope this gives you some insight, but please don't take my scribblings as a definitive description of this small part of the system. Grab a tech manual sometime. You might also find the principals of the air bleed injector different to what many would tell you.
Best of Luck
M
"If the engine is hot, place mixture control in IDLE CUT-OFF, switch auxiliary fuel pump to ON for 30 to 60 seconds, then OFF. Return mixture to full rich and continue with cold start procedure."
There is a little rubber gasket in the fuel control unit, and unless its just been overhauled, it'll always leak a bit at ICO. I havent yet seen a IO-520 that didnt register some fuel flow at ICO.
Bevan..
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Hot Starting A Fuel Injected Engine??
I'm reading a really good book by Chris Markham about Fuel Injected engines and there is just something that I need to clarify about my knowledge with Fuel Injected engines.
When a Fuel Injected engine is hot, it forms air bubbles in the fuel lines particulary near the fuel distrubution unit and the injector lines. The method that he and a lot of others prescribe in this situation is to close the throttle, close the mixture control (mixture ICO) and put the fuel pump on so as to squirt fuel into the lines and get rid of the air bubbles BUT this will only work up to the Fuel Control Unit.
Because the mixture is left in ICO, then no fuel will be pumped past this point, but past this point is where air bubbles also exist and I would of thought that the general rule of thumb would be to leave the mixture control rich so that it can get past the fuel control unit and purge those parts of the fuel system from air bubbles as well.
Don't want to leave it in too long as flooding the intake port with fuel will occur which will cause a chemically incorrect mixture so there is a limit but can someone please explain why he and others say to leave the mixture ICO....surely this is not circulating fuel around the entire system right?
Thanks in advance
BK
When a Fuel Injected engine is hot, it forms air bubbles in the fuel lines particulary near the fuel distrubution unit and the injector lines. The method that he and a lot of others prescribe in this situation is to close the throttle, close the mixture control (mixture ICO) and put the fuel pump on so as to squirt fuel into the lines and get rid of the air bubbles BUT this will only work up to the Fuel Control Unit.
Because the mixture is left in ICO, then no fuel will be pumped past this point, but past this point is where air bubbles also exist and I would of thought that the general rule of thumb would be to leave the mixture control rich so that it can get past the fuel control unit and purge those parts of the fuel system from air bubbles as well.
Don't want to leave it in too long as flooding the intake port with fuel will occur which will cause a chemically incorrect mixture so there is a limit but can someone please explain why he and others say to leave the mixture ICO....surely this is not circulating fuel around the entire system right?
Thanks in advance
BK
I'll give it a go. Once past the FCO, fuel is away from any pumps and metering units. This means that there should not be any chance of cavitation in these lines. If there are vapour lock/gas bubbles in the lines up to the divider, they are not of concern once past the fuel pump etc. When you do a circulation with mixture in ICO, you are getting rid of hot fuel/vapour (in the fuel pump and FCU) in exchange for cooler fuel that the fuel pump and FCU can pump as well as meter. The same with Diesel injection pumps and air. Once you bleed the injection pump, Air will be expelled from the lines and injectors in due course.
Any clearer??
Any clearer??
Silly Old Git
Hot start from 30 odd years ago.
Fuel injected
Mixture rich /Throttle closed
Hit the primer and open throttle until you see the fuel flow .STOP!
Mixure idle cut off
Throttle set
Kick it in the guts
Mixture to rich when it fires.
(Throttle jiggling as required for extra pax appeal)
Adjust sunglasses and smoothly taxi over the chocks .
(Hows me memory Chuckles?)
Fuel injected
Mixture rich /Throttle closed
Hit the primer and open throttle until you see the fuel flow .STOP!
Mixure idle cut off
Throttle set
Kick it in the guts
Mixture to rich when it fires.
(Throttle jiggling as required for extra pax appeal)
Adjust sunglasses and smoothly taxi over the chocks .
(Hows me memory Chuckles?)
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Tinpis, you forgot one thing - hang arm out of the window (if possible - it may be a little hard in a Cherokee).
The final step, advancing the mixture to rich once the engine fires, is extremely important - especially when a testing officer is sitting next to you. This can be quite embarassing when after four attempts you still haven't worked it out and the testing officer throws his headset into his lap.
Alfred
The final step, advancing the mixture to rich once the engine fires, is extremely important - especially when a testing officer is sitting next to you. This can be quite embarassing when after four attempts you still haven't worked it out and the testing officer throws his headset into his lap.
Alfred
Thread Starter
speaking from experience there Alfred? hehe.
BK- I started a thread like this that got some comprehensive replies only a month ago. A search with the words "starting a hot fuel inj engine" should turn it up.
BK- I started a thread like this that got some comprehensive replies only a month ago. A search with the words "starting a hot fuel inj engine" should turn it up.
Woomera, Perhaps you could merge this with
Chadzat's earlier thread on this.
BK- I started a thread like this that got some comprehensive replies only a month ago. A search with the words "starting a hot fuel inj engine" should turn it up.
Originally Posted by tinpis
Hot start from 30 odd years ago.
Fuel injected
Mixture rich /Throttle closed
Hit the primer and open throttle until you see the fuel flow .STOP!
Mixure idle cut off
Throttle set
Kick it in the guts
Mixture to rich when it fires.
(Throttle jiggling as required for extra pax appeal)
Adjust sunglasses and smoothly taxi over the chocks .
(Hows me memory Chuckles?)
Fuel injected
Mixture rich /Throttle closed
Hit the primer and open throttle until you see the fuel flow .STOP!
Mixure idle cut off
Throttle set
Kick it in the guts
Mixture to rich when it fires.
(Throttle jiggling as required for extra pax appeal)
Adjust sunglasses and smoothly taxi over the chocks .
(Hows me memory Chuckles?)