Help Me With My Hot Start Technique (or Lack Thereof)

[Sheriff23]

67 M20F

1. Set 1200 RPM for 30 seconds

2. Mixture cutoff

3. Do not move throttle

4. Hot start - Crank and add mixture in when it catches

Perfect start every time

[Ragsf15e]

On 10/10/2024 at 11:43 AM, bigmo said:

I do sincerely appreciate everyone's feedback. But the "don't touch anything" method did not work for me. It's why I'm gathering as much info as I can so I can see what works for my plane. @N204TA process is close to what my source (and this guy DOES know his stuff) said to try. 

I do find it interesting that MS tends to really follow Mooney factory guidance on just about everything BUT starting. The Mooney cold and hot starting procedures are literally never recommended. About the only logic I find in the POH is their hot start procedure will surely flood it, so it's ALMOST like they want you to just flood it and move to flooded start.

I will have the mag timing checked and can pull and check plugs, but the plane is 20 hours out of annual and has < 100 hours on the mags. Starter & battery both good.

 

One other aspect of the starting ignition system that is often overlooked… is your sos strong?  They don’t often fail, but they’re also not looked at very often.  I didn’t see anyone mention this, but I think a 1970 F has the sos vs an impulse coupled mag.  If your sos is getting weak, you could still have spark, a good mag, good plugs, but not as strong as it should be (maybe it’s corroded after 50 years).  Just saying that might be something to consider.

[EricJ]

The only times I've had trouble with hot starts have been at high DA.    I visited a high-altitude airport a week or two ago where the DA was about 11000 feet.   It did the usual thing where it'd start and run for a few seconds but wouldn't stay running.   It occured to me to use the trick to turn the electric boost pump on once it started, and that worked really well to keep it running.   That cures vapor lock at the mechanical pump, so at least in my case that's apparently what makes some high DA starts difficult.

[Shadrach]

@bigmo I’ve been flying a lot in the last week behind two different injected Lycoming four cylinders. I haven’t done a single leg over 70NM. This means I’ve done about 10 hot starts in the last 10 days.  Both aircraft (Decathlon and Mooney Exec) start flawlessly hot or cold. They both have the same injection system and engine configuration (IO320 and IO360 with RSA injection). One has Bendix mags with SOS and the other has slicks with an impulse coupling. Hot start turnaround varied between 15 minutes and one hour. OAT varied from 45° to 85°. Technique has been the same for both…Turn the key and add mixture when it fires. I thought about this thread and your airplane on every one of those hot starts. there has to be more to the story with your Aircraft than technique.

[ArtVandelay]

I think it helps to have a throttle set a little higher (1200+ rpms), so there’s a little more fuel flowing to cool the fuel lines.

[802flyer]

I struggled with hot starts when I first got my F model. Mags were due for overhaul and the ignition harnesses were ratty; that said, cold starts were fine and my LOP mag checks per Savvy did not show any abnormalities so I was initially hesitant to blame the equipment and figured I was doing something wrong. Eventually did the mag overhaul and put in a set of Maggie harnesses when the plane was next down for maintenance, and everything got better. I spent a while agonizing over technique, but now agree with others that you should carefully consider an ignition problem rather than something you’re doing wrong in the cockpit.

Just to add another technique you could try: I tend to shut down the engine between 1100-1200rpm as others have mentioned. When ready to start, don’t touch anything; if you feel compelled to do something, advance the throttle another eighth inch but leave the mixture and pump alone. Then start cranking. After a very short shutdown to refuel, it should catch pretty quickly without other intervention.

If a couple seconds have gone by with no firing (common with a 15-60min hot start), I will slowly advance the mixture until it catches, while continuing to crank. When first trying this, figure on 2-3 real seconds of easing the mixture forward. It will start to catch a bit, and then as you go another half inch forward, it’ll actually start and run smooth (by hot start standards anyway). Over time, I got a knack for what mixture position runs smooth with this method, so now I advance more directly to that spot rather than a slow push through the stumbling-because-still-too-lean region. This is also the spot I push the mixture to during any other start attempt (cold starts or if it fires right up during the do-nothing phase of hot starting).

I’ve flown just over 60hrs in the last 30 days (most if it concentrated in two busy weeks with multiple legs per day), mostly in 80-90deg heat, so did quite a few hot starts and didn’t have any tricky starts using the above technique. It’s usually started in under 5sec of total cranking time (either fires right off or it’s time to give it the appropriate lean mix), so not particularly hard on the starter.

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[Shadrach]

On 10/10/2024 at 2:43 PM, bigmo said:

 

I do find it interesting that MS tends to really follow Mooney factory guidance on just about everything BUT starting. The Mooney cold and hot starting procedures are literally never recommended. About the only logic I find in the POH is their hot start procedure will surely flood it, so it's ALMOST like they want you to just flood it and move to flooded start.

I will have the mag timing checked and can pull and check plugs, but the plane is 20 hours out of annual and has < 100 hours on the mags. Starter & battery both good.

 

What manual are you reading? The 67 AFM gives no instruction regarding hot starts. The 1968 AFM does but it is poorly worded. “Normal start” is referenced but not defined. It’s clearly not a cold start. So I’ve always read it as exactly what we’re recommending. Do you have a later AFM with a different hot start procedure?

 

[802flyer]

Yes, that's the gear clicker I was referencing.
My F takes 4 secs for the fuel pressure to stabilize at 25psi. I was giving it 4 secs past pressure built, but will reduce that to 2 and even 1 and try those options. 
That said, my cold starts are 1-4 blade events.

FWIW, I tend to let pressure stabilize with the mixture closed and then push the mixture in, count to 5-one-thousand, pull the mix to cutoff, and then turn off the pump. In my mind, this is a more standard dose of fuel since there’s no possibility for a variable amount of time/fuel before it reaches pressure. I also do this at WOT which again, eliminates differences in fuel dose due to variance in throttle position. I then reset the throttle and crank.


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[Barneyw]

I think there is a good article at Pelican's Perch on this noting that the one hour mark is the critical point.

Generally speaking the engine should fire up easily within a hour after shutdown. After an hour it's time to use the fuel pump to purge the fuel lines. But like everything hot engines, it's not always that simple.

Lately I have been have good success with cranking the engine and if it fires all good and well but if it fires and then dies I will crank the engine and give it a momentary blip of fuel on the pump while cranking and that has worked every time. Takes a little coordination but quite doable. 

Cheers

[varlajo]

6 minutes ago, Barneyw said:

I think there is a good article at Pelican's Perch on this noting that the one hour mark is the critical point.

Generally speaking the engine should fire up easily within a hour after shutdown. After an hour it's time to use the fuel pump to purge the fuel lines. But like everything hot engines, it's not always that simple.

My IO-360-A1A refuses to start following POH procedure or any internet voodoo in the period 15-60 minutes after shutdown. I successfully use hot start procedure before and normal procedure after this period. 

[bigmo]

I agree 15-60 seems to be my black hole too.

All great info folks. I have linked up with a local A&P that owns a Mooney and we're going to check out the SOS and the key switch to make sure I don't have an ignition issue. I found an article by Don Maxwell that spoke of a symptom where releasing the key rapidly while spinning will yield a start - and I've noticed that is indeed when my does. Could be that the SOS is not getting the right activation from the key or the SOS has issues. I believe mine does not activate with just key on (it comes on with key on and push). Seems BK has a couple of different key designs that Mooney used). 

So, we'll check all the possible culprits. Plugs, key switch, SOS...and see if there's something going on there.

[Kelpro999]

1 hour ago, bigmo said:

Don Maxwell that spoke of a symptom where releasing the key rapidly while spinning will yield a start -

 Caution , that will allow the right mag to fire advanced and at low rpm. Damaging kick backs occur.

[Pinecone]

Although it can also mean your switch is miss wired, so it is always trying to start on the right mag.  And when you release to both, it allows the left to fire and it starts.

[bigmo]

Yeah, I’m going to have him check the wiring for sure. It seems like more a/c have it wired to have the SOS on before the push, but I did see the key wiring (and found a few threads here) where it’s correct to have it come on in the push. Seems odd Mooney tried a couple different approaches.

[Fly Boomer]

On 10/22/2024 at 4:16 PM, bigmo said:

Yeah, I’m going to have him check the wiring for sure. It seems like more a/c have it wired to have the SOS on before the push, but I did see the key wiring (and found a few threads here) where it’s correct to have it come on in the push. Seems odd Mooney tried a couple different approaches.

These birds are old, so anything is possible.  Mine energizes the SOS when the key is turned to the "Start" position, and energizes the starter when pushed.

[Shadrach]

On 10/22/2024 at 12:33 PM, Barneyw said:

I think there is a good article at Pelican's Perch on this noting that the one hour mark is the critical point.

Generally speaking the engine should fire up easily within a hour after shutdown. After an hour it's time to use the fuel pump to purge the fuel lines. But like everything hot engines, it's not always that simple.

Lately I have been have good success with cranking the engine and if it fires all good and well but if it fires and then dies I will crank the engine and give it a momentary blip of fuel on the pump while cranking and that has worked every time. Takes a little coordination but quite doable. 

Cheers

One can always add fuel, taking it away is more difficult. If the engine is warm, just try starting it. You’ll soon know if it needs a prime.  Like so many things aviation related, this subject is made more complicated than need be.

[bigmo]

So, I decided to use the excuse to add some parts. I find a great deal on a NOS SlickStart. To the door for $700 seemed a no brainer. I’d spend that much troubleshooting… I also got new plugs.

The plane is going in for some routine maintenance in two weeks and at least I’ll reset things to a bit of a known condition. My plugs are 500 hours & 19 years old…so that felt prudent. The SkickStart is a way to just avoid troubleshooting a SOS that is bad, is going bad, or will go bad.

Im optimistic I’ll be a Jedi hot starter in a few weeks.

[Ragsf15e]

10 minutes ago, bigmo said:

So, I decided to use the excuse to add some parts. I find a great deal on a NOS SlickStart. To the door for $700 seemed a no brainer. I’d spend that much troubleshooting… I also got new plugs.

The plane is going in for some routine maintenance in two weeks and at least I’ll reset things to a bit of a known condition. My plugs are 500 hours & 19 years old…so that felt prudent. The SkickStart is a way to just avoid troubleshooting a SOS that is bad, is going bad, or will go bad.

Im optimistic I’ll be a Jedi hot starter in a few weeks.

If nothing else, you’ll narrow it down to mag, wire harness, or technique!

[PT20J]

The hot starting techniques are all variations of getting the mixture right to fire. Normally, you set the throttle and fiddle with the fuel: ICO when it's hot and if it doesn't light off you know that it needs more gas and you can advance the mixture while cranking until it fires. Some shorten the process by hitting the boost pump momentarily to refill the lines if it's been sitting a while. 

All the standard hot start techniques assume that there is a strong properly timed spark. It's time to check out the ignition system if reasonable techniques do not work.

[Shadrach]

2 hours ago, bigmo said:

So, I decided to use the excuse to add some parts. I find a great deal on a NOS SlickStart. To the door for $700 seemed a no brainer. I’d spend that much troubleshooting… I also got new plugs.

The plane is going in for some routine maintenance in two weeks and at least I’ll reset things to a bit of a known condition. My plugs are 500 hours & 19 years old…so that felt prudent. The SkickStart is a way to just avoid troubleshooting a SOS that is bad, is going bad, or will go bad.

Im optimistic I’ll be a Jedi hot starter in a few weeks.

Should cost almost nothing to determine if you have a good TDC spark from your existing SOS.  Folks really are trying to lead you towards a satisfactory outcome.  I’ve started lots and lots of injected Lycomings both hot and cold. In the event that an engine is hard to start (hot or cold), there has always been an ignition issue. After market solutions are normally added when an operator has identified a weak spot in the design that can be improved upon. It sure looks like you have an ignition issue. A malfunction is not the same thing as a design flaw.

[varlajo]

3 hours ago, bigmo said:

So, I decided to use the excuse to add some parts. I find a great deal on a NOS SlickStart. To the door for $700 seemed a no brainer. I’d spend that much troubleshooting… I also got new plugs.

 

Is there one more where that one came from? 

[bigmo]

I hope my plan doesn’t come off as disrespectful in any way / I need my plane for work, so this seemed a prudent way to eliminate what seems to be a pretty common problem. The SOS is 54 years old…so I feel it’s served its purpose. 
The PIREPs (here) on SlickStart seem overwhelming positive. I didn’t want to drop MSRP for it, but 1/2 MSRP made sense. I’m gambling a little that my SOS has issues. But not gambling that’ll eventually have issues (even if it doesn’t right now). 

[Teddyhherrera]

On 10/20/2024 at 9:51 AM, Sheriff23 said:

67 M20F

1. Set 1200 RPM for 30 seconds

2. Mixture cutoff

3. Do not move throttle

4. Hot start - Crank and add mixture in when it catches

Perfect start every time

I used this method every time up until a week ago. (See my thread about maybe replacing a cylinder.) A local guru (not my AP) told me it's no wonder I have wet plugs with that procedure and what I'm doing is washing the oil off the walls with the fuel. I was having somewhat violent shut downs also. (shaking hard, etc)

I tried his method which is almost the same and it seems way nicer on the engine. T

 

he only change is: throttle at idle.

 

My mind was blown! My shutdown and hot start was sooo silky smooth. 

[MikeOH]

36 minutes ago, Teddyhherrera said:

I used this method every time up until a week ago. (See my thread about maybe replacing a cylinder.) A local guru (not my AP) told me it's no wonder I have wet plugs with that procedure and what I'm doing is washing the oil off the walls with the fuel.

I'm confused....if you read step 4 the mixture is at CUTOFF until the engine fires. How does your 'local guru' explain where all the fuel to wash oil off the cylinder walls is coming from?

[ArtVandelay]

67 M20F
1. Set 1200 RPM for 30 seconds
2. Mixture cutoff
3. Do not move throttle
4. Hot start - Crank and add mixture in when it catches
Perfect start every time

This is overly complicated:

If you Set RPMs to 1200 when you shut down the engine, then it’s:

1. Crank and add mixture when it catches.

If it doesn’t seem to want to start after 30 seconds, give the starter time to cool and then do a flooded start.