Hot start question

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deaston

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Dan
I think I somewhat understand the reasons for shutting down piston engines with the mixture cutoff (safety, eliminating fuel that could get stale, etc). However on the injected 182 I fly, hot restarts on hot days can be very challenging. So much so that I try to plan not to have stop and restart the engine.

Any reason why you shouldn't just shutdown using magnetos and then fire it right back up without any priming? I'm really just thinking about very short stop/starts to let passengers on/off and such.

Help me understand why this is a terrible idea.

Thanks
 
That probably won't work, the fuel left in the fuel lines to the injectors is vaporizing due to the heat, the mixture knob just cuts the flow, the lines remain full of fuel.
This is how it's been explained to me.
The weird part is starting the engine with mixture in cutoff position.
You have a TCM or Lycoming engine?
Have you tried your method, might work if it's a very short stop, also might flood the engine?
 
Presumably this is a newer 182 with an injected Lycoming in it?

If so, what's your hot start procedure? I'm guessing I know what the Cessna manual suggests for a hot start, and that procedure works for many engines. It has not worked for me on the injected Lycomings in Aztecs however. When I hot start an Aztec I'll shut down normally, then when I'm ready to go I just flip the master and the magneto switches on and start cranking. I do not prime it at all, nor do I touch the mixture lever until it fires. I start cranking with the throttle fully open and slowly close it as I crank. It will usually catch at about 1/2 throttle, then the mixture goes rich.

This procedure might work in your case as well. I have not flown or tried to start an injected 182 so I can't speak from experience.
 
Some seaplane guys kill it with mags, sposed to make restarts easier, also it doesn't give the plane that last burst of throttle, which is isn't helpful with docking.

The bad part is it leaves some fuel in the cylinders which can strip some of the oil off, that said I'm not too sure how big of a issue this is seeing some planes actually came with oil/fuel dilution systems for cold weather ops.

What I've done,
Option 1
Shutdown with mixture
When I fire up I don't prime,
Mixture rich,
Slowly advance throttle as I'm cranking

Option 2
Mixture ICO

Throttle full in

Crank

Once she kick I enrich the mixture and pull the throttle to idle at the same time

Between the two it's always worked great for me


Here's a topic in it, lots of float and backcountry guys commenting, much more of a time till engine start critical setting
https://www.backcountrypilot.org/forum/tcm-io520-hot-start-16125
 
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If you're restarting like that, you should be able to shut down using ICO, then restart using the normal procedure sans the priming step of kicking the pump on for a few.
 
I shut mine down with mags when I know the next start is going to be hot. My Bo is very difficult to hot start. When shutting down with everything primed the fuel doesn't seem to boil and heat when restarting. I start normally with the fuel pump on the low setting.

I can't see any issues with what the OP wants to try....
 
I had a heck of a time restarting my Lycoming IO-360 after the engine was hot until I figured out how to reliably start it. As a pilot friend of mine told me... If the engine won't start the problem is either too much fuel i.e.(not enough air) or not enough fuel. One or the other. With the IO-360 restarting I could reliably flood the engine if hot starting I turned on the boost pump AND/OR primed the engine. If I'm just refueling, the most likely starting condition for my IO-360 is that there's too much fuel in the system. So...start with about 3/4 to 1 inch open throttle (vs 1/2 in cold) and start mix at idle cut off. Turning the key will add some useful air to the cylinders and slowly move the mix forward at about 1/2 way forward it catches and starts, back off throttle almost immediately.

I also by this method figured out finally how to restart the engine after it floods which fortunately happens very rarely now that I've figured out the hot start. If flooded, wait a couple minutes, set throttle pretty much wide open, and mixture at idle-cut off. Now when you're turning the starter you are just introducing air into the cylinders (and a good amount pretty quick it will catch, drop the throttle back quick and advance mix halfway.

That's not necessarily POH approved so it's just my way of doing it, but if you think...I either need a. more fuel in the cylinder or b. more air in the cylinder and work to achieve the right mix...It's a lot easier to figure out what you're doing. Honestly, I've read plenty of people talking about this vapor lock thing...but I don't know that I've ever truly experienced it, the biggest problem for me on a hot restart is too much fuel and not enough air.

Edited to add: AND here's the kicker if you're wide-open throttle and mix is at idle cutoff, turning the engine IS adding something to the cylinders...it's just AIR. That was kind of a key revelation for me (I know seems basic but still), and sometimes AIR is all the engine really wants.
 
If its hot, I try a flood start first. (What I did was pull the mixture all the way out (no fuel) and push the throttle all the way in (max air). And keep cranking, don't pump the throttle. Then when it kicks and goes a bit, quickly push the mixture in and pull the throttl to idle (I really need three hands). Your flood start procedure may be different.

If that doesnt do it, I try a normal start with priming.

If that doesnt do it, try a flood start again.

If that doesnt do it, go in and have a cup of coffee.

Every engine seems to have its idiosynchrasies. My carbed Lycoming 0360 simply refuses to be flooded so its normal start every time EXCEPT, when it is hot, it needs 1/2 to 3/4 throttle, way more throttle than when cold. Go figure.

One of them, when it coughed, the procedure was to release the key to stop cranking (ignition still on) and it would start. Like the prop had to slow down for it to start. All I know is it worked.
 
I think the vapor lock can be a little more difficult in the big bore conti fuel objected planes.
 
Checkout_my_Six said:
I shut mine down with mags when I know the next start is going to be hot. My Bo is very difficult to hot start. When shutting down with everything primed the fuel doesn't seem to boil and heat when restarting. I start normally with the fuel pump on the low setting.

I can't see any issues with what the OP wants to try....
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You have a Continental I assume, their FI is different than Lycomings, completely different procedures.
 
James331 said:
I think the vapor lock can be a little more difficult in the big bore conti fuel objected planes.
Click to expand...
I thought it was easier, the continentals have a return line and you just turn on the boost pump to flush fuel lines removing the vapor.
Lycomings don't have return line, so you just end up flooding the cylinders.

This is my understanding, I've only flown with Lycomings.
 
not all TCMs have the return (mine doesn't)....the red headed step child versions do not and will easily flood.
 
My hot start procedure that I use across all airplanes:

Throttle cracked (cracked, not that 1/4" B.S.), Mixture cutoff, No prime, Pump off.

-Start cranking
-As soon as that first cylinder fires (and I mean as soon as, not half a second later), throw the boost pump on.
-Immediately move over and bring the mixture up to full rich

You may need to open the throttle a bit to keep it alive, but it will be a nice, smooth start with the rpm never exceeding 1,000.
 
I've had my plane (182T) for over 4 years now and I still can't figure out how to make the hot start work every time on this IO-540! Every time i tried what worked last time and it doesn't work and needs some new procedure!

However starting with the mix all the way, I've seen this done, and I've done it on mine many times in the past and it works surprisingly good. Prime it for half the time you normally need, leave the mixture and just crank the starter, it catches basically instantly. I haven't done this in a long time as I'm not sure its effects on the engine, but I can tell you this, now that its being discussed again I'm going to have to ask my mx guy and see his take, if it doesn't harm the engine I'm starting it that way every time.
 
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I've never had an issue hot starting the Arrow (Lycoming IO 360) after shutting it down with the mixture. There is plenty of fuel remaining.
 
Glad to see its not just me having restart issues. I guess that's issue - I'm looking for a reliable technique as it seems a bit of guesswork and feel.

This a 182S, so lycoming. Problem seems to be having to guess between two opposite possible conditions as weather gets warmer: fuel boiling and creating vapor in the lines displacing fuel (therefore, not enough fuel) and flooding due to running fuel pump too long trying to clear vapor out of lines. I thought that if the stop is short enough (2-3 min) maybe stop/start with just mags/starter might be the way to go.

POH is ambiguous on this topic ("In warmER weather... temperature MAY increase... after APPROXIMATELY 30 minutes... SOME priming COULD be required", blah, blah)

So far, I haven't heard any reasons NOT to try it...
 
In my Cardinal (IO-360), hot starting is easy for the first 5 minutes or so by just using normal start procedure (no priming). After 60 minutes or so, use cold start procedure. Between 10 and 60 minutes, no guarantees but usually I can get it started with minimal priming. If that fails, I've found it best to wait 60 minutes and do a cold start. I've had self-appointed "experts" try their favorite techniques during that iffy 10-60 minutes and totally flood the engine. The POH hot start procedure is definitely NOT reliable on this engine.
 
To the OP look at your engine manual the instructions may differ from the Aircraft Mfg. POH.

Checkout_my_Six said:
I shut mine down with mags when I know the next start is going to be hot. My Bo is very difficult to hot start. When shutting down with everything primed the fuel doesn't seem to boil and heat when restarting. I start normally with the fuel pump on the low setting.

I can't see any issues with what the OP wants to try....
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I hear ya brother! I have a J35 Bo with the Conti IO 520. I have spent many a summer afternoon cursing at the plane, opening up the cowl to cool things off and sitting in the FBO lounge for an hour or so. I have found that the procedure in the Engine Manual works well. Mixture cut off. Throttle full forward. Run the boost pump for 1 minute. Then prime and do a normal start. The boost pump sends enough cool fuel through the lines to condense the fuel vapors back to liquid form.
 
mondtster said:
Presumably this is a newer 182 with an injected Lycoming in it?

If so, what's your hot start procedure? I'm guessing I know what the Cessna manual suggests for a hot start, and that procedure works for many engines. It has not worked for me on the injected Lycomings in Aztecs however. When I hot start an Aztec I'll shut down normally, then when I'm ready to go I just flip the master and the magneto switches on and start cranking. I do not prime it at all, nor do I touch the mixture lever until it fires. I start cranking with the throttle fully open and slowly close it as I crank. It will usually catch at about 1/2 throttle, then the mixture goes rich.

This procedure might work in your case as well. I have not flown or tried to start an injected 182 so I can't speak from experience.
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Hot starts on the Aztec are a beech.

I do the same thing you do but leave the thottle full open while cranking. The engines always catch, but only run for a couple of revolutions and then seem to run out of fuel no matter how quick I open the mixture. I've tried "tickling" the mixture before cranking - part way to rich and right back to ICO, and that seems to help sometimes, but not consistently. Ignition system is in top condition with serviced mags, new harnesses and I service & rotate the plugs every 75 - 100 hrs.

I am going to try your "close the throttle slowly" procedure next time. Thanks!

I had to replace a starter last year and ended up with a Skytec which spins the engine faster, and that side seems to hot start more readily now. Stronger magneto spark?
 
coloradobluesky said:
If its hot, I try a flood start first. (What I did was pull the mixture all the way out (no fuel) and push the throttle all the way in (max air). And keep cranking, don't pump the throttle. Then when it kicks and goes a bit, quickly push the mixture in and pull the throttl to idle (I really need three hands). Your flood start procedure may be different.
.
Click to expand...

I used this procedure when I flew a Lance. Worked great.
 
This topic as as many answers as there are engines.

My version goes something like this...

stopping for 1 - 15 minutes
Carve runes and pray to the Nordic Gods

16 - 20 minutes
Sacrifice a chicken

21 - 30 minutes
Look for a witch

31 minutes
Get some coffee and relax while enjoying the sights. (works every time)

My last choice seems to work every time but works better if pie and icecream are involved.
 
This was my exact method as well with my Lycoming IO-360 until a year ago where a sage man told me to open the throttle and mixture for 10 sec let the pressure off...back to Idle and idle cutoff and then crank and slowly open the mixture...fires every time now when hot....chickens were getting expensive...and opening everything up prior to crank seems to remove the vapor lock...if that's what it was...
 
In the 182Ts, I'll try a no-prime start like the POH says. If the crank has NO hint of combustion, I'll prime just enough for the fuel flow to lift off zero. Otherwise, advance the throttle and keep cranking. I find in practice that these airplanes usually do need a little prime on a cool day.

The point of the ICO crank is to start a bit too rich and let the crank lean it until it fires.
 
If our cars and pick-ups were this difficult to start under any condition we'd have them back at the dealership and be beating on the Service Dept manager. :D
 
you don't want an un-vented fuel system....with all the eco crap on your plane. :no:
 
My T182T lives in a hot area and loves the prime.

Hot engine or cold engine, this Lyc TIO-540 prefers me to crack the throttle 1/2", hit boost (fuel pump switch) and advance mixture full forward and count to five after fuel flow is indicated. Then mixture to idle cut-off, turn off boost, hit the crank and advance mixture once the engine catches. If it stumbles, I'm ready again quickly with the boost.

I'm told this is unusual, but it works.
 
oilburner said:
My T182T lives in a hot area and loves the prime.

Hot engine or cold engine, this Lyc TIO-540 prefers me to crack the throttle 1/2", hit boost (fuel pump switch) and advance mixture full forward and count to five after fuel flow is indicated. Then mixture to idle cut-off, turn off boost, hit the crank and advance mixture once the engine catches. If it stumbles, I'm ready again quickly with the boost.

I'm told this is unusual, but it works.
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Sounds like a pretty typical flood start... Just pump gas in it until you know the lines are liquid and let it turn until it's ready to combust. I can't imagine why it'd be a problem or unusual.
 
The owner of a local flight school helped me out one day when I was having trouble starting one of his rentals. He had me, with mags and masters off, push the throttle and mixture to full increase and then count to 10, then proceed with a normal start but no prime. It worked first time. Since then, I've used this procedure pretty effectively for a warm fuel injected engine.

The Continental IO-470 in the Beech Mentors like the hot start method in the POH (mixture idle-cutoff, throttle full increase, crank then be ready to slam the mixture in and chop the throttle as soon as it fires). But, like an earlier poster said, you need 3 hands.
 
I discovered why this is a bad idea after trying it. Silly engine doesn't want to quit when mags are cut. Coughed and sputtered until I decided I better pull the red knob.
 
Had this problem with an Arrow this past weekend. Had 5 good starts and on the sixth the engine..DID..NOT..WANT to start. Tried priming, tried full lean, full open, etc. Thought I might have a real problem and then finally got it going. And of course, it happened on the last leg of my 7 hour cross country when I really just wanted to get home :(
 
deaston said:
I discovered why this is a bad idea after trying it. Silly engine doesn't want to quit when mags are cut. Coughed and sputtered until I decided I better pull the red knob.
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That's not good! I'd get that checked if I were you. No spark == engine should stop. Sounds like you're still getting some spark even when you turn the mags off.
 
bikert said:
That's not good! I'd get that checked if I were you. No spark == engine should stop. Sounds like you're still getting some spark even when you turn the mags off.
Click to expand...

Hmm... I was guessing it was more like "dieseling" in a hot engine, but maybe not? This says not an issue in FI engines, but wondering if something is different about aviation engine FI (fuel injection mechanically linked to engine turning?)

http://www.badasscars.com/index.cfm...duct_id=94/category_id=13/mode=prod/prd94.htm


Don't we have some mechanics around here that can set us straight on this hot start stuff??? Reading through these posts, looks like part science part voodoo. My favorite, fool-proof solution: Go inside and drink a cup of coffee...
 
A&P/IA here....dieseling?...meh, no, sounds more like an open in a Mag lead or bad switch. Once fuel is cut with the mixture....no fuel is available to keep the engine going.
 
deaston said:
I discovered why this is a bad idea after trying it. Silly engine doesn't want to quit when mags are cut. Coughed and sputtered until I decided I better pull the red knob.
Click to expand...

bikert said:
That's not good! I'd get that checked if I were you. No spark == engine should stop. Sounds like you're still getting some spark even when you turn the mags off.
Click to expand...

Yeah, off the cuff that sounds like a mag grounding issue. It may very well just be a single mag with a bad ground.
 
Checkout_my_Six said:
A&P/IA here....dieseling?...meh, no, sounds more like an open in a Mag lead or bad switch. Once fuel is cut with the mixture....no fuel is available to keep the engine going.
Click to expand...

Not trying to argue with you, as I'm not a mechanic, but to be clear, I'm not making up that term:

"Finally, a few words regarding the ICO function. Selecting the mixture control to full "LEAW' cuts off the fuel feed to the carburetor, and causes the engine to stop immediately ..... which is the reason why this lever is painted red. The idle cutoff system is much more efficient to stop the engine than switching off the magnetos. Indeed, by this latter method fuel still flows to the cylinders, albeit at a much lower rate due to the near idle power throttle setting, until the propeller stops completely. This may give way to self-ignition, or pre-ignition, due to hot carbon deposits in the cylinder, and cause the engine to continue turning unevenly for a while, a phenomenon known as "dieseling", and possibly even to produce harmful backfiring"

Came from this site: http://www.new.aerocollege.eu/page/PilotsNotes/67/IBASICPRINCIPLESOFLIGHTAIRCRAFTENGINES.html
 
GRG55 said:
If our cars and pick-ups were this difficult to start under any condition we'd have them back at the dealership and be beating on the Service Dept manager. :D
Click to expand...

I flew with a friend a few months ago and and the 1981 172P fired up about twice as fast as the 2014 Toyota somethingorother. Since it wasn't my car I thought it was pretty funny :cool:
 
Warlock said:
This was my exact method as well with my Lycoming IO-360 until a year ago where a sage man told me to open the throttle and mixture for 10 sec let the pressure off...back to Idle and idle cutoff and then crank and slowly open the mixture...fires every time now when hot....chickens were getting expensive...and opening everything up prior to crank seems to remove the vapor lock...if that's what it was...
Click to expand...
That was the advice the local mechanic gave me, it does seem to work but you still have to crank for a few seconds, I think it makes every hot start consistent.
 
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