How long for a hot start

[ArtVandelay]

Great point, Ross.
Here’s how the RSA manual describes it. 

 

Note 4.3 about RPMs we discussed earlier.

I wonder what they mean by “prime” (they have it quoted)?

[jaylw314]

29 minutes ago, ArtVandelay said:

Note 4.3 about RPMs we discussed earlier.

I wonder what they mean by “prime” (they have it quoted)?

I assume "prime" refers to the act of squirting fuel into the intake manifold, since Lycoming primers squirt it directly into the cylinders?

[Shadrach]

7 minutes ago, jaylw314 said:

I assume "prime" refers to the act of squirting fuel into the intake manifold, since Lycoming primers squirt it directly into the cylinders?

Lycoming primers are plumbed to the intake manifold not the cylinder. Think of all of the needless challenges that would be associated with a direct to cylinder primer.

[ArtVandelay]

Lycoming primers are plumbed to the intake manifold not the cylinder. Think of all of the needless challenges that would be associated with a direct to cylinder primer.

So they mean full rich and boost pump on until fuel pressure rises?

[Sue Bon]

20 minutes ago, ArtVandelay said:

So they mean full rich and boost pump on until fuel pressure rises?

I'm so glad you asked this question! 

FYI, I just had a couple of hot starts in Spain at 32C+  weather after shutdowns that were between 30 min and 1.5 hours. I tried all the tips I learned here: opening cowl flaps during descent, opening oil door on the ground during shutdown, not too much throttle during the start. I had the boost pump on, but didn't touch the mixture until starting. My engine started right up without any fuss to maintain the desired rpm. No problems at all. Thanks a lot for all your help on this. It was a timely thread for me.

[jaylw314]

1 hour ago, Shadrach said:

Lycoming primers are plumbed to the intake manifold not the cylinder. Think of all of the needless challenges that would be associated with a direct to cylinder primer.

I worded that wrong, I recalled the primer line in the old Cherokee I flew going into the cylinder head (not the cylinder itself)? I recall that specifically because the dang thing kept fatiguing and breaking off at the connector.

OTOH, if primer lines can go in different places on Lycomings, I guess that's not what they were talking about...

Edited August 24, 2022 by jaylw314

[jaylw314]

1 hour ago, Sue Bon said:

I'm so glad you asked this question! 

FYI, I just had a couple of hot starts in Spain at 32C+  weather after shutdowns that were between 30 min and 1.5 hours. I tried all the tips I learned here: opening cowl flaps during descent, opening oil door on the ground during shutdown, not too much throttle during the start. I had the boost pump on, but didn't touch the mixture until starting. My engine started right up without any fuss to maintain the desired rpm. No problems at all. Thanks a lot for all your help on this. It was a timely thread for me.

32C??  I thought Spain was supposed to be a furnace during the summer? 

[Sue Bon]

9 hours ago, jaylw314 said:

32C??  I thought Spain was supposed to be a furnace during the summer? 

It feels like it! Portugal is next forecast is up to 36C, but we will see....

[aviatoreb]

What’s the don maxwell procedure?  Would someone please link me?

[ArtVandelay]

What’s the don maxwell procedure?  Would someone please link me?

Don’t touch anything, just start it, when it turns over, push mixture in.
Yeah, that simple.

[aviatoreb]

3 hours ago, ArtVandelay said:

Don’t touch anything, just start it, when it turns over, push mixture in.
Yeah, that simple.

???!!! Really?  I gotta see a YouTube for that!

so last touched I turned the engine off by pulling out the mixture starving the engine for fuel.

So hot start I crank like that?  Why would it start even a little in that stat ?  Is that what you mean by turns over?

[ArtVandelay]

???!!! Really?  I gotta see a YouTube for that!
so last touched I turned the engine off by pulling out the mixture starving the engine for fuel.
So hot start I crank like that?  Why would it start even a little in that stat ?  Is that what you mean by turns over?

It will turn over/cough/pop, cylinders will fire because there’s still some fuel in the lines but will die quickly if you’re slow on the mixture (1st sign of life, go full rich or equivalent if at higher altitudes). If it starts but is rough cause it’s really hot, then boost pump and slowly increase throttle to push more fuel and air to cool the lines to prevent vaporization.

I’m no expert, but that’s how it was explained to me. Someone here can probably detail the magic of the fuel system.

Note: for Lycomings IO360 only.

[Ragsf15e]

37 minutes ago, ArtVandelay said:

It will turn over/cough/pop, cylinders will fire because there’s still some fuel in the lines but will die quickly if you’re slow on the mixture (1st sign of life, go full rich or equivalent if at higher altitudes). If it starts but is rough cause it’s really hot, then boost pump and slowly increase throttle to push more fuel and air to cool the lines to prevent vaporization.

I’m no expert, but that’s how it was explained to me. Someone here can probably detail the magic of the fuel system.

Note: for Lycomings IO360 only.

Nope, that covered it pretty well.  Exactly like that starts mine right up whether 30 minutes or 3 hours.  

[EricJ]

17 hours ago, jaylw314 said:

I worded that wrong, I recalled the primer line in the old Cherokee I flew going into the cylinder head (not the cylinder itself)? I recall that specifically because the dang thing kept fatiguing and breaking off at the connector.

OTOH, if primer lines can go in different places on Lycomings, I guess that's not what they were talking about...

It sprays on the back of the intake valve around the stem area.    On a fuel injected engine the injector nozzles go in the same place.

 

[EricJ]

1 hour ago, aviatoreb said:

???!!! Really?  I gotta see a YouTube for that!

so last touched I turned the engine off by pulling out the mixture starving the engine for fuel.

So hot start I crank like that?  Why would it start even a little in that stat ?  Is that what you mean by turns over?

The vid was posted earlier in the thread, but it certainly doesn't hurt to post it again if it's useful.    Remember this is for Lycomings with Bendix RSA fuel injection.   This is not a procedure for starting a Continental engine.
 

 

[PT20J]

One reason I think some have trouble starting is that they don't open the throttle far enough before cranking. The Lycoming recommendation is 1/4 throttle travel. I don't find I need this much throttle, and I don't like it that far open because it's likely to rev pretty high if it does start cleanly, but every time it doesn't start right away it's because I didn't have the throttle open enough. Also, the RSA servo has a linkage between the throttle and the mixture (the length of this linkage is what you change to adjust idle mixture) and it won't admit much fuel to the injectors unless the throttle is open about 1/4 travel or more during priming.

Skip

[jaylw314]

1 hour ago, EricJ said:

It sprays on the back of the intake valve around the stem area.    On a fuel injected engine the injector nozzles go in the same place.

 

Ah, cool beans, thanks.  I still haven't had a chance to actually peek around a carbureted O-360

[EricJ]

1 hour ago, jaylw314 said:

Ah, cool beans, thanks.  I still haven't had a chance to actually peek around a carbureted O-360

I don't think any carbureted Mooneys have that kind of priming system, but lots of other older airplanes do.   Usually the priming injector only goes to one cylinder.

 

[Raymond J1]

 

It takes a while...

Edited August 25, 2022 by Raymond J

[zehutiman]

Do we have any Continental IO550 users out there that would share their hot start techniques?  Lately, I’ve been having a lot of difficulty getting my engine restarted.  It does the classic, run then stop.  I’ve seen many variations suggested, especially regarding the boost pump…some say to run it 15 seconds, some advocate 30-60 seconds.

,

[Shadrach]

54 minutes ago, zehutiman said:

Do we have any Continental IO550 users out there that would share their hot start techniques?  Lately, I’ve been having a lot of difficulty getting my engine restarted.  It does the classic, run then stop.  I’ve seen many variations suggested, especially regarding the boost pump…some say to run it 15 seconds, some advocate 30-60 seconds.

,

If you’re running the pump at idle cut off, I don’t think it matters much how long you run it as the fuel is being circulating from the servo back to the tank. 

[Pinecone]

When I was flying a lot in IO-550 T-34s with short times between formation flights for practice, we all just did the flooded start.

Prime

Throttle - Full

Mixture - Idle Cut Off

Crank until it fires, throttle almost closed, then mixture full rich.

Worked every time.

[Shadrach]

1 hour ago, Pinecone said:

When I was flying a lot in IO-550 T-34s with short times between formation flights for practice, we all just did the flooded start.

Prime

Throttle - Full

Mixture - Idle Cut Off

Crank until it fires, throttle almost closed, then mixture full rich.

Worked every time.

Nice… Especially with a ground crew standing by to deal with any fires. I have seen Mooneys catch fire during a flooded starts.

[zehutiman]

8 hours ago, Shadrach said:

If you’re running the pump at idle cut off, I don’t think it matters much how long you run it as the fuel is being circulating from the servo back to the tank. 

That’s what I’ve been doing (idle cutoff).  If you run the pump with the mixture full rich, that’ll flood it, right?

[A64Pilot]

16 hours ago, zehutiman said:

Do we have any Continental IO550 users out there that would share their hot start techniques?  Lately, I’ve been having a lot of difficulty getting my engine restarted.  It does the classic, run then stop.  I’ve seen many variations suggested, especially regarding the boost pump…some say to run it 15 seconds, some advocate 30-60 seconds.

,

My 520 when hot would start, then try to die, many pump the throttle which I don’t think does anything as there is no accelerator pump, I would turn the boost to low boost and she would pick right back up, if not it would die. Many seemingly Bo drivers for some reason start at high RPM, the excess RPM gets them through the lean die off period. but starting one immediately to 2000 RPM is I think a very bad idea myself. I like it to turn until oil supply is established then start, many newer cars operate that way, fuel injectors are disabled until there is oil pressure. I’m not saying spin it until the gauge comes up but three or four blades go by and you have oil flow.

Running the pump at idle cut off on a Conti circulates cool fuel through the system and is a good idea before attempting a start in my opinion. If done at idle cut off it’s not putting fuel into the engine but circulating fuel that returns to the tank.

Lycoming does not have a fuel return so you can’t circulate fuel so running boost at ICO just pressurized the system there is no flow