Hot start or cold start?

[MATTS875]

Question, you land and come back say 3 hours later. Do you hot start the plane or cold start?

[smccray]

Look at the engine monitor and check the CHTs and oil temps.  If it's hot then hot start.  After 3 hours of sitting it's a cold start in TX.

[jaylw314]

That'd be cold start.  I'm guessing any fuel in the intake manifold has evaporated after 3 hours, so there's nothing left to ignite.  A hot start is a hot start not because the engine is warm, but because the intake is flooded (and the fuel divider lines boil off) after shutdown, so it can be easily overprimed.  Give it enough time to evaporate and it's no longer a hot start.

[MATTS875]

Thanks for the advice.

12 minutes ago, smccray said:

Look at the engine monitor and check the CHTs and oil temps.  If it's hot then hot start.  After 3 hours of sitting it's a cold start in TX.

 

9 minutes ago, jaylw314 said:

That'd be cold start.  I'm guessing any fuel in the intake manifold has evaporated after 3 hours, so there's nothing left to ignite.  A hot start is a hot start not because the engine is warm, but because the intake is flooded (and the fuel divider lines boil off) after shutdown, so it can be easily overprimed.  Give it enough time to evaporate and it's no longer a hot start.

Thanks for the advice. I just wanted to make sure. I overprimed one time before and it was a difficult process getting it to start

[jaylw314]

4 minutes ago, MATTS875 said:

Thanks for the advice.

 

Thanks for the advice. I just wanted to make sure. I overprimed one time before and it was a difficult process getting it to start

If there's ever a question of whether you overprimed, just crank like a flooded start--throttle full, mixture idle, crank and reduce throttle if it starts.  If nothing happens in 7-8 seconds of cranking, you're not flooded--wait a minute for the starter to cool, then do the cold start again.

[INA201]

I did this just yesterday.  I set up throttle/mixture for cold start but only primed for 1/2 a second or so just to kick the pressure a little. It fired right off.

[MATTS875]

6 minutes ago, INA201 said:

I did this just yesterday.  I set up throttle/mixture for cold start but only primed for 1/2 a second or so just to kick the pressure a little. It fired right off.

I think I primed too long and flooded it the last time. I will short prime it this time. Thanks

[jaylw314]

10 minutes ago, INA201 said:

I did this just yesterday.  I set up throttle/mixture for cold start but only primed for 1/2 a second or so just to kick the pressure a little. It fired right off.

I wonder if flipping the pump switch on and off like that can hurt the pump.  If I plan on doing a short prime, I turn the pump on, then open and close the mixture knob instead.

[smccray]

9 minutes ago, MATTS875 said:

Thanks for the advice. I just wanted to make sure. I overprimed one time before and it was a difficult process getting it to start

Now your question makes more sense.  New plane right?

Better to underprime vs overprime, but you have to protect the starter.  Over time you'll get comfortable with how the plane runs.  Starting my old J was a little odd.  The first time engaging the starter would almost always fail on a cold start.  The second time it would fire right up.  It sounded like BS when I bought the plane, but it was absolutely true.  Hot starts weren't any big deal- she fired right up.

Since we're going into fall/winter... I've read that when it's cold it's good to wait a little longer between prime / starter engagement to give the fuel a little more time to mix in the cylinder and to be ready to fire up.  I never noticed any difference, but it makes sense to me.

[MATTS875]

8 minutes ago, smccray said:

Now your question makes more sense.  New plane right?

Better to underprime vs overprime, but you have to protect the starter.  Over time you'll get comfortable with how the plane runs.  Starting my old J was a little odd.  The first time engaging the starter would almost always fail on a cold start.  The second time it would fire right up.  It sounded like BS when I bought the plane, but it was absolutely true.  Hot starts weren't any big deal- she fired right up.

Since we're going into fall/winter... I've read that when it's cold it's good to wait a little longer between prime / starter engagement to give the fuel a little more time to mix in the cylinder and to be ready to fire up.  I never noticed any difference, but it makes sense to me.

Yes, new plane to me. still learning the planes characteristics. Thanks

[jaylw314]

13 minutes ago, smccray said:

Better to underprime vs overprime, but you have to protect the starter.  Over time you'll get comfortable with how the plane runs.  Starting my old J was a little odd.  The first time engaging the starter would almost always fail on a cold start.  The second time it would fire right up.  It sounded like BS when I bought the plane, but it was absolutely true.  Hot starts weren't any big deal- she fired right up.

My guess is that on cold starts, you have to run the pump longer to clear out the vapor in the fuel lines.  The fuel flow when you prime with the throttle open only a 1/4" is pretty darned slow, so it's more like 7 seconds of priming.   My instructor taught me 5 seconds, so it almost always seemed to take 2 tries until I primed for a little longer.

If I open the throttle 1/4 open instead, it only takes 3-4 seconds of priming.  Unfortunately, I imagine everyone's motor is a little bit different

[Yetti]

Cold

1" of throttle, fuel pump on, open mixture

count to 6

close mixture

start. 2 handed dance to bring throttle down to 1100 rpm and mixture about 1/3 of way up

Hot

Shutdown: Shut off mixture with 1" of throttle open at 1100 rpm

Start:  don't touch anything, don't turn on fuel pump.   

Crank till pops, slowly open mixture.

 

Feel cowl to see if warm or cold start applies.

[Ragsf15e]

Cold vs Hot depends on lots of factors like wind/parking direction, temperature and time.  You may not know for sure.  I use 100 degrees oil temp as a rough guide... however, if in doubt, I’ll always try a hot start procedure first because no fuel is added-just crank it like you left it shutdown.  If it doesn’t work, you can always add fuel for a normal cold start.  However, If you prime for the first start you are stuck with that fuel and can easily be stuck flooding it and moving to a flooded start if it was hot.

Theres lots of techniques for each.  Don’t burn up your starter.

Edited October 29, 2018 by Ragsf15e

[DonMuncy]

3 hours ago, MATTS875 said:

Yes, new plane to me. still learning the planes characteristics. Thanks

It took me 2 years to learn how to start mine.

[jaylw314]

11 minutes ago, DonMuncy said:

It took me 2 years to learn how to start mine.

I thought I was a complete failure at starting until I found out my left mag had a bad e-gap.  Now I think I'm god-like at starting 

[toto]

5 hours ago, MATTS875 said:

Question, you land and come back say 3 hours later. Do you hot start the plane or cold start?

I would almost always use a hot start first. There's a Don Maxwell video that covers this pretty well. 

 

[Yetti]

The hard one was.   Start up move 50 feet, realize the baggage door is not secured.  Shut down.  Hop out.  Now what.   Tried a crank.   Then 3 seconds of fuel pump.  Started up.

[Hank]

1 hour ago, Yetti said:

The hard one was.   Start up move 50 feet, realize the baggage door is not secured.  Shut down.  Hop out.  Now what.   Tried a crank.   Then 3 seconds of fuel pump.  Started up.

Man, ya'll are making me love my C model more and more! Hot starts take me about 3-4 more blades than a cold start, and use less throttle . . . . . Ain't nothing else different.  

[Ragsf15e]

Yeah but we save enough gas running LOP to make up for buying all the new starter motors!

[EricJ]

1 hour ago, Yetti said:

The hard one was.   Start up move 50 feet, realize the baggage door is not secured.  Shut down.  Hop out.  Now what.   Tried a crank.   Then 3 seconds of fuel pump.  Started up.

I've found that, too, that if in doubt priming for just a couple of seconds instead of a full five or six count works well.

[Yetti]

7 hours ago, Hank said:

Man, ya'll are making me love my C model more and more! Hot starts take me about 3-4 more blades than a cold start, and use less throttle . . . . . Ain't nothing else different.  

Same with a hot start on a IO.   But mid warm after a couple minutes of running was the confusion....

[MATTS875]

Did the cold start last night and worked perfect. Thanks for the advice and the video