Cold & Hot Start on F

[mooneyflyer]

What are people’s Cold and Hot Start procedures on an F? A friend just bought an F and asked me.

[TTaylor]

The search engine inside MooneySpace is not great.  Go to Google and search "Mooney hot start MooneySpace". You will find many threads on the subject.

[ArtVandelay]

When looking at recommendations, make sure they are talking about Lycoming IO360, procedures for carburetor engines or TCM engines are completely different.

[Ross Taylor]

This thread's a good place to start... but you'll see that there are almost as many techniques as there are pilots.

 

[Ragsf15e]

48 minutes ago, mooneyflyer said:

What are people’s Cold and Hot Start procedures on an F? A friend just bought an F and asked me.

Hot starts, takeoff flaps, true airspeed, touch and goes, lean of peak vs rich of peak... ask any of them and you may find a 47 page thread on mooneyspace.  Everyone has a technique and/or opinion.

 

Bottom line -

Cold start, follow checklist, prime with fuel pump.

Hot start is anytime airplane has been run in the last 12 hours.  Don’t prime it.  Just leave it like shutdown (1000rpm throttle, mixture cutoff).  Crank it.  Mixture rich when it fires.

You didn’t ask about flooded start, but you’ll certainly need that if you tried the cold start technique on a warm engine or if you mess up the hot start.  Flood it.  Full throttle.  Mixture cutoff.  Crank it while Slowly reducing throttle until it fires.  Then mixture rich and throttle idle.

[PT20J]

Use the procedure in the POH. On a hot start, if it doesn’t start, prime it and use the flooded start procedure. 

Skip

[carusoam]

DMax has a video that covers the details that can be used on any Mooney...

But... Any Mooney pilot then has to know some specifics about his engine plumbing....
 

Best regards,

-a-

[JimB]

Someone posted the fuel injection manuals the other day. I found their recommend starting technique interesting

 

Edited July 23, 2020 by JimB

[J0nathan225]

I was messing this up yesterday resulting in a RoN (storms all around really made the decision easy).  When doing a flooded start don't get too excited and add mixture too early.  Let the engine really get a firing before giving it fuel.  I kept adding fuel after a few cylinders fired: pop pop pop  added fuel... no more pops.  After waiting and hearing pop, pop, pop, pop, pop, engine actually catching its breathe THEN add fuel was SUCCESSFUL. 

[MBDiagMan]

Cold: mixture rich, throttle slightly open, fuel pump 2 seconds, start it up. 
 

Hot:  leave everything as it was when killed.  Start cranking and move mixture slowly forward and it lights off.  Slowly is a rate that would get the mixture full rich in about 1 1/2 or 2 seconds.  
 

Thats what works for me.

[Ragsf15e]

16 hours ago, PT20J said:

Use the procedure in the POH. On a hot start, if it doesn’t start, prime it and use the flooded start procedure. 

Skip

Skip, no!!! After your 1500+ posts of awesome advice and help, I’ve got to disagree with this one. 

Cold start, agree, poh.  But if it’s warm and you prime it, you’re not gonna start it.  You’re guaranteeing yourself another start attempt (wearing starter) as a flooded start.  Done right, it’s probably ok.  I’ve done it myself for sure, but I think your chances of a tailpipe fire are much higher on a flooded start.

Just do what works for 95% of the E/F guys (me included)... leave it set as shutdown, crank it, add mixture when it fires.  Simple.  If that doesn’t work for some reason, sure flood it, but never flood it first because you can’t take that back.

[PT20J]

36 minutes ago, Ragsf15e said:

Skip, no!!! After your 1500+ posts of awesome advice and help, I’ve got to disagree with this one. 

Cold start, agree, poh.  But if it’s warm and you prime it, you’re not gonna start it.  You’re guaranteeing yourself another start attempt (wearing starter) as a flooded start.  Done right, it’s probably ok.  I’ve done it myself for sure, but I think your chances of a tailpipe fire are much higher on a flooded start.

Just do what works for 95% of the E/F guys (me included)... leave it set as shutdown, crank it, add mixture when it fires.  Simple.  If that doesn’t work for some reason, sure flood it, but never flood it first because you can’t take that back.

I agree with you. What I said though was that if that doesn’t work for some reason ( the usual reason is that it’s cooled long enough that it’s somewhere between a hot start and a cold start) then prime it and use the flooded start procedure. This avoids not knowing if it is not starting because there is too much fuel or not enough (and burning up the starter or running down the battery trying to figure it out). The idea is to get into a known condition (slightly flooded) and then use a procedure that works for that condition. 
 

Skip

[Ragsf15e]

18 hours ago, PT20J said:

Use the procedure in the POH. On a hot start, if it doesn’t start, prime it and use the flooded start procedure. 

Skip

I guess from this (above) I took it to mean follow the poh on both hot and cold.  My 1968 POH doesn’t differentiate and “Engine Start” primes with the fuel pump.  So the poh works great for cold but if you follow it for hot start you’re likely flooded, but sometimes not quite and it’s not a good place.

[Marauder]

I guess from this (above) I took it to mean follow the poh on both hot and cold.  My 1968 POH doesn’t differentiate and “Engine Start” primes with the fuel pump.  So the poh works great for cold but if you follow it for hot start you’re likely flooded, but sometimes not quite and it’s not a good place.

As someone who after 30 years has tamed the IO-360 beast in my F model, Rags is spot on about the hot start. I am pretty anal about making sure that I am idling at 1,000 RPMs when I pull the mixture for shutdown. No need to temp the hot start demons by shutting down at 800 or 1,200 RPMs.

Where people get into trouble is in that post 30 minute zone. Is it hot, is it really just super warm or just warm?Some are tempted to treat it as a cold start at this point. Not me! After casting out the evil demon spirits on the cold start, you ain’t catching me with a Ouija board asking if it is cold enough.


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[PT20J]

I didn't know that Mooney left the hot start procedure out of some manuals. Don't know why as it's been the same forever on all RSA fuel injected Lycomings.

It might be best to review the theory. Gasoline will only combust over a fairly narrow range of fuel/air ratios. When the engine is running, the fuel injection system controls this. Starting is more difficult. Too much fuel (relative to air) and it won't start. Too little fuel and it won't start. How to get it right? 

For the cold start we prime which leads to a slightly rich (too much fuel) condition. As we crank, the fuel gets used up and eventually the mixture is within the ignition range and it starts. (It's really a bit more complicated than this as the fuel has to vaporize and mix with the air to form a combustible mixture which is why it's harder to start when it's really cold). 

Why are hot starts more challenging? When the engine shuts down, a valve in the flow divider shuts off fuel to the injectors to give a clean shut down. Still though, some fuel remains in the lines. If you restart within a few minutes, there is enough fuel in the lines to get the engine to start. If you wait longer, the fuel evaporates and you will need to prime. How long between not needing to prime and needing to prime is dependent on both time and ambient temperature. Only experience will guide you here.

Why does it work to run the engine to 1000 rpm and shut down and then restart when still hot without touching anything? With a hot start, there is an unknown amount of fuel in the lines to the injectors. Immediately after the shutdown, there is some. A day later there is none. In between -- who knows? So, the biggest problem is introducing too much air. Most people open the throttle too much. Try shutting down at 1000 rpm and then close the throttle. Notice how little it is open. 

Skip

 

[Guest]

Along with fuel/ air ratios, condition of the ignition system and the battery, cables and starter motor pay an important part in ability to hot start the engine.

Clarence

[MARZ]

I followed this advice for mine - never failed..

 

 

[eman1200]

47 minutes ago, MARZ said:

I followed this advice for mine - never failed..

 

 

has never worked one time for me.  got my own process that works, I'll keep using that.

[ArtVandelay]

has never worked one time for me.  got my own process that works, I'll keep using that.

It works well for short stops, notice he only shuts down for a minute.

[carusoam]

Adding variables adds to the challenge...

So...

Starting with the throttle in the same position every time... miraculously removes the variable of air flow rate from the equation.... Hence the reason people select 1krpm...

The need for a hot start can be defined by the sound of fuel bubbling in the injection system... if you hear fuel boiling... it has the tendency to blow liquid fuel towards the injectors... followed by vapor bubbles showing up when you expect liquid fuel....

Eliminate these three additional variables and starting gets much easier...

+1 for having a strong battery and starter....
+1 for having DMax explain the hot start logic... (video above)
+1 for knowing how to get cool fuel to your engine prior to a hot start... It helps a little to have a fuel return line like a Continental engine....

+1 for knowing how to manage a flooded start...

It helps to have a few blades go by before making any changes...

PP thoughts only, not a mechanic...

Best regards,

-a-

[Guest]

7 hours ago, ArtVandelay said:

It works well for short stops, notice he only shuts down for a minute.

Even my IO-720 starts that easily after 30 seconds.  Wait a half hour or more for a real challenge.

Clarence

[mooneyflyer]

Thanks to all for your help.  Gotta love the folks on MooneySpace.  

[Ragsf15e]

On 7/23/2020 at 8:31 PM, PT20J said:

I didn't know that Mooney left the hot start procedure out of some manuals. Don't know why as it's been the same forever on all RSA fuel injected Lycomings.

It might be best to review the theory. Gasoline will only combust over a fairly narrow range of fuel/air ratios. When the engine is running, the fuel injection system controls this. Starting is more difficult. Too much fuel (relative to air) and it won't start. Too little fuel and it won't start. How to get it right? 

For the cold start we prime which leads to a slightly rich (too much fuel) condition. As we crank, the fuel gets used up and eventually the mixture is within the ignition range and it starts. (It's really a bit more complicated than this as the fuel has to vaporize and mix with the air to form a combustible mixture which is why it's harder to start when it's really cold). 

Why are hot starts more challenging? When the engine shuts down, a valve in the flow divider shuts off fuel to the injectors to give a clean shut down. Still though, some fuel remains in the lines. If you restart within a few minutes, there is enough fuel in the lines to get the engine to start. If you wait longer, the fuel evaporates and you will need to prime. How long between not needing to prime and needing to prime is dependent on both time and ambient temperature. Only experience will guide you here.

Why does it work to run the engine to 1000 rpm and shut down and then restart when still hot without touching anything? With a hot start, there is an unknown amount of fuel in the lines to the injectors. Immediately after the shutdown, there is some. A day later there is none. In between -- who knows? So, the biggest problem is introducing too much air. Most people open the throttle too much. Try shutting down at 1000 rpm and then close the throttle. Notice how little it is open. 

Skip

 

Skip I have to apologize, Mooney did provide hot and flooded start guidance in the manual, it’s just not the way people normally get successful hot starts.  The manual has the pilot prime for a hot start to “flush the fuel lines with cool fuel” and then quickly crank.  It says to crank quickly to avoid the fuel percolating.  I have not had success with this technique.  By not priming, I’ve had easy hot starts even several hours after shutdown.

Their flooded technique is fine.

[PT20J]

3 hours ago, Ragsf15e said:

Skip I have to apologize, Mooney did provide hot and flooded start guidance in the manual, it’s just not the way people normally get successful hot starts.  The manual has the pilot prime for a hot start to “flush the fuel lines with cool fuel” and then quickly crank.  It says to crank quickly to avoid the fuel percolating.  I have not had success with this technique.  By not priming, I’ve had easy hot starts even several hours after shutdown.

Their flooded technique is fine.

No apology necessary. I wasn’t aware of that procedure in the manual for your airplane, and it’s a strange one. I think if you use that technique, you will have to use the flooded start procedure to get it started.

[Ragsf15e]

2 hours ago, PT20J said:

No apology necessary. I wasn’t aware of that procedure in the manual for your airplane, and it’s a strange one. I think if you use that technique, you will have to use the flooded start procedure to get it started.

Yes definitely, it will be flooded if you do this which is funny because the flooded start technique appears right after it and mirrors what you said about flooded start.