Cold Start Thread

[INA201]

How long do you guys hit the boost pump prior to cold starting?  Sometimes I fire off on first blade and sometimes it takes a few rotations.  I think I've always boosted too long but just curious. 

[1964-M20E]

I do an 8 count and it usually starts right up with little or no problems.

 

 

[Bob_Belville]

It takes about 5 seconds in the case of my E model for the fuel pressure to peak. Perhaps a little longer if cold.

[Oscar Avalle]

In my C model, I turn on the boost pump until I get fuel pressure, then I turn it off. Mix rich and pump the throttle three times. Wait one minute and crank.


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[neilpilot]

2 minutes ago, Oscar Avalle said:

In my C model, I turn on the boost pump until I get fuel pressure, then I turn it off. Mix rich and pump the throttle three times. Wait one minute and crank.


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I'm sure that works fine, but I follow the POH for my 65C.  I leave the boost pump on while I pump the throttle and crank.  Pump is switched off after the engine start.

[Yetti]

One inch of throttle.

boost pump on move mixture to full.

Count 6 seconds.

Move mixture to cut off.

Turn off boost pump.

Turn key

Move mixture to half when it fires.

Reduce throttle to 1100 rpms

 

[Oscar Avalle]

37 minutes ago, neilpilot said:

I'm sure that works fine, but I follow the POH for my 65C.  I leave the boost pump on while I pump the throttle and crank.  Pump is switched off after the engine start.

Yes, I know. However, with my engine I had a harder time starting with the boost pump on... go figure

[Shadrach]

There is no exact answer.  It depends on the weather, even with a preheat.  Fuel atomizes readily when it is warm and being injected into a warm manifold.  Not so much in the winter when the fuel in the wings is cold and the manifold if preheated to just 40-50df. Cold weather will require a longer prime.  I prime with the throttle wide open (hat tip to Byron) and the mixture full rich until pressure peaks plus 2 full seconds in the winter time. In the summer I prime until pressure peaks. It's important to ALWAYS remember to return the throttle to the cracked position.  If it's winter time and I find that I've under primed, I sometimes just push the mixture to full rich while I continuing to crank.

[Guitarmaster]

WOT, full rich mixture, pump for about 4 seconds (6 when c o l d), let it sit for about five to ten seconds, crack the throttle and let her rip.  First or second blade every time!

[carusoam]

Measuring the fuel going to a carb'd engine...

electric pump to pressurize the system.  Then pump off, Pump throttle til the pressure is gone...  really cold?  Repeat.

This was a method I used on my C to deliver a consistent quantity of fuel to the start event...

i also used a number of throttle pumps related to the temperature.

below 30° and above 20°F without preheat uses a lot of fuel.  Much of it drains on the NLG.

pre-heat works better...

Below 20°F, only pre-heat would work...

Best regards,

-a-

[KLRDMD]

3 hours ago, Oscar Avalle said:

In my C model, I turn on the boost pump until I get fuel pressure, then I turn it off. Mix rich and pump the throttle three times. Wait one minute and crank.

Sounds like witchcraft.

[KLRDMD]

3 hours ago, Shadrach said:

Fuel atomizes readily when it is warm and being injected into a warm manifold.  Not so much much in the winter when the fuel in the wings is cold and the manifold if preheated to say 40-50df. Colder weather will require a longer prime.

40-50ºF  *is* colder weather to me !!

[Shadrach]

11 minutes ago, KLRDMD said:

40-50ºF  *is* colder weather to me !!

Yes even cold starts are hot starts in your neck of the woods.

[201er]

I do the following with pretty good success:

Master On

Throttle Full (WOT)

Mixture Full (Rich)

Boost Pump On

Count 6 Mississippis

Mixture Cut Off

Boost Pump Off

*Throttle back to just cracked

**Wait 10-30 seconds

***Start

 

*I usually set the throttle right past the point where I feel the click for the gear warning circuit, about 1/4"

**I usually wait longer in winter than in summer for the fuel to vaporize. This little bit of wait can help a lot.

***When it's cold in winter, particularly if the plane was sitting or I could not get a preheat, the last thing I do before cranking for the start is get out (with the mags and master off) and turn the prop about 6 times (3 full rotations) by hand. I treat it like a hot prop as though I am hand propping just in case for safety. Then I jump back in and it fires on the first or second blade. This helps a lot in winter because the battery is outputting poorly and the starter is making pathetic wimpy turns. This way I save the couple turns it will make before it fires by doing it by hand and let it get right to the point of having a quick start.

For a hot-start, I put mixture cut off and throttle full and start cranking. When it seems about ready to fire or if a few seconds have gone by, I bring the throttle back to normal starting position and keep cranking till it fires.

[Hank]

6 hours ago, Oscar Avalle said:

In my C model, I turn on the boost pump until I get fuel pressure, then I turn it off. Mix rich and pump the throttle three times. Wait one minute and crank.


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I run  the fuel pump on my C until fuel pressure peaks and stops increasing, then turn it off. Mixture to Rich and pump the throttle, watching fuel pressure drop with each stroke. Normal start is 2 pumps, as temp drops I pump more, peaking at 4-5 (my coldest start was 8°F with 5 pumps). In cold weather (<40°F), I wind and set the yoke clock then put on my headset. Next is turn the key and push. 

When it's really cold (well below freezing), after unplugging the engine heat I move out of the hangar and pull the prop through two full rotations before climbing in and following the above.

[PTK]

This is my cold start:

Fuel selector fullest tank, mixture full rich, fuel pump on for 8 sec then off, mixture ICO, don't touch throttle...its already at ~1000 RPM from previous shutdown, wait a few sconds, turn key. Ready with mixture rich once she fires. Don't need full rich mixture. Only as much mixture as needed. Not full rich. Lean brutally for ground ops.

Fires up in one blade most of the time.

[ArtVandelay]

This is my cold start:
Fuel selector fullest tank, mixture full rich, fuel pump on for 8 sec then off, mixture ICO, throttle is already at ~1000 RPM from previous shutdown, wait a few sconds, turn key. Ready with mixture rich once she fires. Don't need full rich mixture either...only as much as she needs. Lean brutally for ground ops.
Fires up in one blade most of the time. 

Ditto except count is higher in colder weather.

[Shadrach]

1 hour ago, 201er said:

I do the following with pretty good success:

Master On

Throttle Full (WOT)

Mixture Full (Rich)

Boost Pump On

Count 6 Mississippis

Mixture Cut Off

Boost Pump Off

*Throttle back to just cracked

**Wait 10-30 seconds

***Start

 

*I usually set the throttle right past the point where I feel the click for the gear warning circuit, about 1/4"

**I usually wait longer in winter than in summer for the fuel to vaporize. This little bit of wait can help a lot.

***When it's cold in winter, particularly if the plane was sitting or I could not get a preheat, the last thing I do before cranking for the start is get out (with the mags and master off) and turn the prop about 6 times (3 full rotations) by hand. I treat it like a hot prop as though I am hand propping just in case for safety. Then I jump back in and it fires on the first or second blade. This helps a lot in winter because the battery is outputting poorly and the starter is making pathetic wimpy turns. This way I save the couple turns it will make before it fires by doing it by hand and let it get right to the point of having a quick start.

For a hot-start, I put mixture cut off and throttle full and start cranking. When it seems about ready to fire or if a few seconds have gone by, I bring the throttle back to normal starting position and keep cranking till it fires.

Interesting,  I cannot feel the gear horn switch click when moving the throttle. It functions as it should, but there is no sign mechanically that it is lnked to the throttle.

[Raptor05121]

My gear horn clicks on the throttle, but my throttle is very old and creeps forward. Very hard to keep on top of is when aligning for a landing.

 

[bradp]

If anyone has the opportunity and they have a fuel injected engine - I'd highly recommend doing a baby bottle test at next annual or whenever the injectors are next off (or, do them with the injectors on).  It's very eye opening what the differences in throttle position and mixture position mean in terms of flow to the cylinders. It's helpful for me to visualize when I'm doing starts in various temperature conditions just how much fuel I think I'm putting in the cylinders.

 

One caveat is to PTKs is that throttle position for 1000 rpm is slightly different with a hot engine compared to a completely cold engine.  Not a whole lot, but noticeable.

 

201er makes a good point that waiting for fuel to vaporize can be a real bonus for easy starts. 

 

[Shadrach]

43 minutes ago, Raptor05121 said:

My gear horn clicks on the throttle, but my throttle is very old and creeps forward. Very hard to keep on top of is when aligning for a landing.

 

You have a vernier throttle correct? There should be no creeping if unless the friction lock is loose or malfunctioning. Tighten it or get it fixed, it will come back to bite you some day. It might creep forward on descent, but in climb it will likely creep towards the closed position as soon as you reach for the gear, or make an adjustment o flaps or trim.  A throttle that does not stay where it is set is not good.

[Hector]

Alright keep it coming! I want to see if we reach 50 variations on how to start a Mooney


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[gsxrpilot]

TSIO360MB Continental...

Cold start - Hold primer in for 5 seconds. Release and start.

Hot start - Hold primer until sound change, (think Doppler effect), usually about 5 to 8 seconds. Release and start.

[Cyril Gibb]

I've always thought that the flow divider (spider) diaphram was calibrated to evenly divide fuel to each cylinder only when the fuel pressure was within a normal range.  I keep my mixture at ico until the pressure with the electric boost pump is in the green before opening the mixture to prime.  I was concerned that at fuel low pressures, the fuel distribution would be uneven so the chances of the "correct" air/fuel mixture at all cylinders would be reduced.  Works for me.... every time when cold....

 

[ArtVandelay]

I've always thought that the flow divider (spider) diaphram was calibrated to evenly divide fuel to each cylinder only when the fuel pressure was within a normal range.  I keep my mixture at ico until the pressure with the electric boost pump is in the green before opening the mixture to prime.  I was concerned that at fuel low pressures, the fuel distribution would be uneven so the chances of the "correct" air/fuel mixture at all cylinders would be reduced.  Works for me.... every time when cold....
 

Since the time from no pressure to green pressure is only a second and throttle is set to idle, probably not a lot of difference, and cold starts have a wider range on the rich side. Probably not an issue for cold starts, but for hot starts it makes sense to run boost pump before start (see my method in 3003 hot start thread).