A New (for me) Hot Start Technique

[Echo]

My IO-360 is horrible on hot starts (10-15 minutes after shutdown).  The leave everything alone and floded start procedure get no hint of firing.  What I have done twice successfully is put throttle to firewall and crank.  When it fires I bring mixture in and reduce throttle.  I have no idea why, but this works with my engine.  If I slowly bring in mixture before engine fires I get NOTHING.  Anybody else do this or know why this works for my engine?

Edited February 6, 2024 by Echo

[SKI]

So I recently bought a J. My transition instructor tried something the first day at lunch and it didn't work. So in my hotel that night I was searching Mooneyspace and found the below procedure around here somewhere. It's dirt simple and has worked every time I have tried it. I'm usually running in 4-6 blades.

 

#1 Mixture, Prop and Throttle all full forward for 10-12 seconds. No Boost pump.

#2 Mixture Full lean and Throttle about 1000-1200 RPM (Basically cracked open 1/8-3/16 on mine)

#3 Crank till it catches then advance Mixture.

#4 Smile and breath A sigh of Relief you didn't just kill your starter and battery.

 

 

[Shadrach]

9 hours ago, Echo said:

My IO-360 is horrible on hot starts (10-15 minutes after shutdown).  The leave everything alone and floded start procedure get no hint of firing.  What I have done twice successfully is put throttle to firewall and crank.  When it fires I bring mixture in and reduce throttle.  I have no idea why, but this works with my engine.  If I slowly bring in mixture before engine fires I get NOTHING.  Anybody else do this or know why this works for my engine?

Perhaps your idle mixture is on the rich side leaving more unburned fuel in the intake at shutdown? I don’t know why your IO 360 should be any different from any other.  Hot starts are a non issue for my engine.  Shut down at 1000rpm. On start up, treat the engine as preprimed. Leave throttle alone, crank and enrichen when it fires. It usually starts in the first 3 or 4 blades. In the rare instance that it does not, I try a second time to ensure that there is no combustible mixture in the intake. I then prime for a few seconds (3-5 depending on OAT) and try again. I’ve never failed to get it started.

If that method does not work for you, somehing else is going on. What’s the status of the ignition system? SOS or impulse coupling?

[Marc_B]

Disregard and carry on.

 

[Fly Boomer]

3 minutes ago, Marc_B said:

TSIO360.  Most of the time I don't have to do anything with the fuel pump.  From getting fuel (5min between stop to start) to stopping for lunch (1.5 hrs).  I shut down at 1000 RPM.  So for start I push mixture full forward and twist throttle forward a twist or so (I find it stumbles less this way).  Fire up and adjust any stumbling with the throttle.

Rarely I've had to flush the lines with throttle out and mixture to pulled to idle then high boost for 10 sec; then set throttle around 1/3 and advance mixture when it fires.  But I've found that flushing the lines is not typically required for me.

 

Your Continental fuel system bears little resemblance to the fuel system on Echo's Lycoming.  Each engine probably requires its own technique.

[Echo]

21 minutes ago, Shadrach said:

Perhaps your idle mixture is on the rich side leaving more unburned fuel in the intake at shutdown? I don’t know why your IO 360 should be any different than any other.  Hot starts are a non issue for my engine.  Shut down at 1000rpm. On start up, treat the engine as preprimed. Leave throttle alone, crank and enrichen when it fires. It usually starts in the first 3 or 4 blades. In the rare instance that it does not, I try a second time to ensure that there is no combustible mixture in the intake. I then prime for a few seconds (3-5 depending on OAT) and try again. I’ve never failed to get it started.

If that method does not work for you, somehing else is going on. What’s the status of the ignition system? SOS or impulse coupling?

That is what I was thinking.  For some reason my plane is leaving to much fuel in intake at shutdown.  That said, a flooded start does NOT work to get my plane to fire.  I believe it is SOS Ross.  I don't have Skytech starter.  My Skytech spun prop at a significantly higher speed than this OEM starter.

Edited February 6, 2024 by Echo

[Shadrach]

9 minutes ago, Echo said:

That is what I was thinking.  For some reason my plane is leaving to much fuel in intake at shutdown.  That said, a flooded start does NOT work to get my plane to fire.  I believe it is SOS Ross.  I don't have Skytech starter.  My Skytech spun prop at a significantly higher speed than this OEM starter.

Next time you shut down, set it at idle (should be ~650rpm) and slowly pull mixture to ICO. Should see an rpm increase of 25-50 before it quits. If the increase is more than 50 rpm, the idle mixture is too rich.

[Marc_B]

re-read the OP and sure, not the same engine.  But I'm curious if you have a different flooded start procedure for the E?  What the OP is doing I thought sounds exactly like a flooded start procedure.  Throttle firewalled, mixture back until it catches, then mix up and throttle back.

[RoundTwo]

1 hour ago, Echo said:

My IO-360 is horrible on hot starts (10-15 minutes after shutdown).  The leave everything alone and floded start procedure get no hint of firing.  What I have done twice successfully is put throttle to firewall and crank.  When it fires I bring mixture in and reduce throttle.  I have no idea why, but this works with my engine.  If I slowly bring in mixture before engine fires I get NOTHING.  Anybody else do this or know why this works for my engine?

How aggressively do you lean for taxi? I lean the crap out of it and actually use mixture to slow my taxi idle. It’s right on the edge of dying.

For hot starts, I first ran into problems by letting off on the the key about one second early. My hot starts improved drastically when I ignored my mechanic’s gut of “that’s enough” and went one or two seconds longer. My hot starts are now very consistent and predictable, just takes a tad bit longer than the three or four seconds I’m happiest with.

Throttle - cracked

Mixture - idle cutoff 

Crank like in the Don Maxwell video.

[Shadrach]

39 minutes ago, Marc_B said:

TSIO360.  Most of the time I don't have to do anything with the fuel pump.  From getting fuel (5min between stop to start) to stopping for lunch (1.5 hrs).  I shut down at 1000 RPM.  So for start I push mixture full forward and twist throttle forward a twist or so (I find it stumbles less this way).  Fire up and adjust any stumbling with the throttle.

Rarely I've had to flush the lines with throttle out and mixture to pulled to idle then high boost for 10 sec; then set throttle around 1/3 and advance mixture when it fires.  But I've found that flushing the lines is not typically required for me.

 

That might work on a Lycoming in cold weather. In summer, it would likely flood the engine or perhaps make the exhaust go boom.

[Marc_B]

@Shadrach no return line, didn't catch the lycoming.  ha.  disregard.  making coffee now...

[Shadrach]

16 minutes ago, RoundTwo said:

How aggressively do you lean for taxi? I lean the crap out of it and actually use mixture to slow my taxi idle. It’s right on the edge of dying.

For hot starts, I first ran into problems by letting off on the the key about one second early. My hot starts improved drastically when I ignored my mechanic’s gut of “that’s enough” and went one or two seconds longer. My hot starts are now very consistent and predictable, just takes a tad bit longer than the three or four seconds I’m happiest with.

Throttle - cracked

Mixture - idle cutoff 

Crank like in the Don Maxwell video.

This leaning for taxi business as a potential panacea for idle engine problems just confuses the issue. Save for high DA operations, the Lycoming IO360 is designed to be ground operated at full rich and indeed it operates beautifully at that setting. Nothing wrong with ground leaning if that’s your bag. I do, depending on CHTs. However, choosing to or not to ground lean is not what’s causing the start up problem. It’s either technique, fuel or ignition related.

[Ragsf15e]

1 hour ago, Echo said:

My IO-360 is horrible on hot starts (10-15 minutes after shutdown).  The leave everything alone and floded start procedure get no hint of firing.  What I have done twice successfully is put throttle to firewall and crank.  When it fires I bring mixture in and reduce throttle.  I have no idea why, but this works with my engine.  If I slowly bring in mixture before engine fires I get NOTHING.  Anybody else do this or know why this works for my engine?

What you described is (basically) the flooded start procedure (minus applying boost pump to make sure it’s flooded and possibly slowly walking throttle back as it cranks).  I agree that will likely work, but you might look at the ignition system to see why a normal hot start isn’t working.  Mine works just like @Shadrach.  Very very rarely do I “miss” a hot start and have to do a flooded start.  

Edited February 6, 2024 by Ragsf15e

[Shadrach]

Just to be clear, I’ve never flooded the engine intentionally (nor accidentally for that matter). I’ve seen Mooneys (and other makes) catch fire during a flooded starts. The sheath of my ram air cable is melted from what I suspect was a less than optimal flooded engine start long before I started flying. I once saw an E model at the self service post fire. No major damage but required max before returning to service. We had a Stearman on the field that required paint repair after flooded a hot start. Would have been much worse but he stuck with it until it started and extinguished the fire. 
 

[PT20J]

Full throttle and mixture ICO is the flooded start procedure. So, the problem is too much fuel. 

Assuming good mags and plugs, starting is all about getting a combustible mixture of fuel and air in the cylinders. It helps to understand what’s going on. I’ve attached the starting description by the manufacturer of the fuel injection system.

The reason the procedure @SKI suggested works (usually after about half an hour when most of the fuel has vaporized from the lines) is that the heat in the engine compartment vaporizes some fuel in the line between the servo and the fuel pump. Since this fuel is trapped with no where to go, the pressure in this line increases. Opening the throttle and mixture allows this fuel, driven by the pressure in the lines, to prime the engine a bit.

One variable is how tight the mixture valve is in the ICO position. The valve isn’t required to completely shut off the fuel flow and most leak a little in the ICO position. This may allow some fuel to flow through the system driven by the increasing pressure described above affecting the amount of fuel at the cylinders some time after shutdown. This might be why your engine seems to be flooded during warm starts. You can do the test described in the attached excerpt from the RSA troubleshooting manual. 

The procedure @Shadrach suggested works well for me. Since there is no way of knowing how much fuel remains in the lines, start out by assuming there is enough fuel to start in ICO. If not, then prime a bit. I also find that if it doesn’t start in ICO, it will usually start if I put the mixture full rich and keep cranking. I set my throttle to the point where I hear the gear warning switch click.

[Shadrach]

4 minutes ago, PT20J said:

I also find that if it doesn’t start in ICO, it will usually start if I put the mixture full rich and keep cranking. 

I find his works acceptably in cooler weather. In hot weather, not so much. I haven’t much thought about why.

[Echo]

16 minutes ago, Shadrach said:

I find his works acceptably in cooler weather. In hot weather, not so much. I haven’t much thought about why.

OK.  I will give the full rich a try (in cold weather) with throttle at 1000rpm vs. full throttle method I did a couple times (out of necessity).  Some great comments.  Much appreciated.  Scott

[ohdub]

My IO360 won't reliably hot start with the leave everything alone method either. I have come up with my own variation that works everytime however. For me if I shut down with the throttle at 1300-1400 RPM (or open the throttle to approximately that position before starting), then slowly push in the mixture as I crank it'll fire up once the mixture is about 1/4 of the way in. 

I lack the mechanical knowledge to know what that does or why it works, I just know that it works so that's what I do.

Steve

[dzeleski]

@Echo Have you visually checked to make sure your mixture control actually brings the mixture back to the ICO stop on the servo?

Or asked another way, when you pull back to ICO does the engine shut off immediately or does it run on and stumble for a few seconds?

If the cable isn’t reaching ICO the engine will stumble and continue to pull fuel rather than starve, leaving more fuel in the intake when it finally does shut off. Since it’s open more fuel can leak into the intake as the pressure bleeds off. This floods the engine. Then when you go to start again it is able to pull more fuel into the engine making the situation even worse. I had this problem recently when my mixture cable failed.

You also might want to make sure the sniffle valve is clean and free as well.

Edited February 6, 2024 by dzeleski

[Echo]

29 minutes ago, dzeleski said:

@Echo Have you visually checked to make sure your mixture control actually brings the mixture back to the ICO stop on the servo?

Or asked another way, when you pull back to ICO does the engine shut off immediately or does it run on and stumble for a few seconds?

If the cable isn’t reaching ICO the engine will stumble and continue to pull fuel rather than starve, leaving more fuel in the intake when it finally does shut off. Since it’s open more fuel can leak into the intake as the pressure bleeds off. This floods the engine. Then when you go to start again it is able to pull more fuel into the engine making the situation even worse. I had this problem recently when my mixture cable failed.

You also might want to make sure the sniffle valve is clean and free as well.

Mixture idle cutoff is quick and not unusual.

[Shadrach]

9 hours ago, Echo said:

OK.  I will give the full rich a try (in cold weather) with throttle at 1000rpm vs. full throttle method I did a couple times (out of necessity).  Some great comments.  Much appreciated.  Scott

Scott, I got my wires crossed and confused the issue a bit. My engine will COLD start in cool weather with the mixture full Rich and no prime. It takes several blades, but it works. It’s a handy tool to have if you need to start up and taxi with a dead boost pump. I would not advocate flying an aircraft without a working boost pump.

I have never tried it as a hot start procedure and therefore cannot recommend for or against it. However, if Skip says it works, i’m inclined to believe him.

[Shadrach]

I should’ve been more specific with regards to flooded starts. My comments  were directed at the idea of intentionally flooding the engine after a failed hot start in order to start from a “known“ condition.  Significant potential there for things to go pear shaped.

[PeteMc]

Friend used to have TERRIBLE problems with hot starts (212 Trophy).  We'd always hang around wherever we were until he got started and taxied out.  

Then he got a system that seems to work really well: 

1) shutdown at 1300 rpm (not at 1000 rpm idle)

2) If no start, don't over prime (pump on and mixture in only till fuel pressure peaks) and retry

 

[RoundTwo]

5 hours ago, Shadrach said:

This leaning for taxi business as a potential panacea for idle engine problems just confuses the issue. Save for high DA operations, the Lycoming IO360 is designed to be ground operated at full rich and indeed it operates beautifully at that setting. Nothing wrong with ground leaning if that’s your bag. I do, depending on CHTs. However, choosing to or not to ground lean is not what’s causing the start up problem. It’s either technique, fuel or ignition related.

Just passing along what I have found that has worked for me. I didn’t say it was the best way, only way or even a better way, just that it has worked for me. YMMV

Chuck

[ArtVandelay]

So I recently bought a J. My transition instructor tried something the first day at lunch and it didn't work. So in my hotel that night I was searching Mooneyspace and found the below procedure around here somewhere. It's dirt simple and has worked every time I have tried it. I'm usually running in 4-6 blades.
 
#1 Mixture, Prop and Throttle all full forward for 10-12 seconds. No Boost pump.
#2 Mixture Full lean and Throttle about 1000-1200 RPM (Basically cracked open 1/8-3/16 on mine)
#3 Crank till it catches then advance Mixture.
#4 Smile and breath A sigh of Relief you didn't just kill your starter and battery.
 
 

#1 causes residual fuel pressure and fuel vapor to zero, so when new fuel is injected it’s cool preventing further vaporization.