1340 cold start techniques

[Matt Gunsch]

Ken,
that is a great way to get a induction fire, when you pump the throttle you are sending jets of fuel into the blower case, but most if it is coming back down into the carb and airbox where it will pool, if the engine sneezes thru the induction, your carb and airbox will ignite. For a hot start you can try cranking with the mixture in idle cut off and move to rich as it fires, or give it 1/2 to 1 shot of prime, if possible while cranking. It is better to get the fuel into the cylinders than into the blower on starting.

[shrike]

The people at Covington Engine said to run the engine for at least 30 minutes to help burn off the water in the oil and case walls...

Getting it well into operating temperature and keeping it there a while is the key. Actually flying for an hour is even better.
If I had a dollar for every time I've had to explain to a customer why needed new expensive bits in their "Only has 100hrs SMOH (in 1999)" engine, well..I suppose I could buy a really good lunch

[51fixer]

Thanks for the inputs!

Anyone have any techniques on leaving a loaded shot in the primer and adding during the start?

Why ? now you have a load of fuel in the primer that if the engine starts you have to do something with, it is easy enough to operate the primer if you need more.

51fixer, I have seen a number of 6s that unless the mixture is set to rich when using the wobble pump, they pour gas on the ground, I have always started with the mixture full rich as it is a float style carb, not much different than a cessna.

We get a small dribble and then the float seats and it'll be dry. You can see pressure on the gauge come up at the point the seat is made.
We recently changed a carb as it would continuously dribble fuel. The float was partially sunk due to a leak developed. After repair it again seals up.
Had another that developed a leak on the accelerator pump seal.

[Ken Dwelle]

Ken,
that is a great way to get a induction fire, when you pump the throttle you are sending jets of fuel into the blower case, but most if it is coming back down into the carb and airbox where it will pool, if the engine sneezes thru the induction, your carb and airbox will ignite. For a hot start you can try cranking with the mixture in idle cut off and move to rich as it fires, or give it 1/2 to 1 shot of prime, if possible while cranking. It is better to get the fuel into the cylinders than into the blower on starting.

Careful Matt, there's a Warning in section II of the -1 against priming a hot engine because of the possibility of fire. Regarding the backfire, it only happens if the throttle it open too much. This hot start technique is the best I've found in 28 years with the T-6, it's as easy as starting your car. Now if anyone has a good way to hot start an IO-550 Bonanza I'd really like to hear it, that one makes my palms sweat!

Ken

[Taigh Ramey]

I gotta agree with Matt that pumping the throttle without the engine turning causes the accelerator pump to push raw fuel into the throat. Without the engine turning on an updraft system the fuel will pool at the bottom of the induction system. Any back fire at all can easily cause quite a fire. I have repaired a few aircraft that had this very thing happen.

One on a 985 presented itself as an oil leak. On this aircraft the induction runs across the top of cylinders 5 and 6. Inspection revealed that the rubber inter ear rocker oil drain tube couplings of both cylinders were charred crispy by the induction fire. Imagine how long you have to burn a thick walled MIL-H-6000 rubber coupling to get it to start leaking. I couldn't believe that the aluminum ducting wasn't distorted or that anything else had been damaged by the fire.

The only time I will use the throttle on start is if the engine is turning over with the starter motor. Most books are against this procedure because of the induction fire problems mentioned above. For me it has been a very effective method of introducing fuel while starting especially hot starts. Priming gets fuel in in the upper 5 cylinders whereas the accelerator pump will get to all 9. It's not a procedure that I like to teach to new students but it works well for me.

[Flat 12x2]

I know this one is old hat, but it bears repeating loud and often.
Sitting kills engines. The way to achieve the greatest longevity is to exercise the engine often. ie, GO FLY.
The only thing that will kill engines faster than sitting is periodic short runs. the classic, "I went out and started it up every month to keep the oil moving."
When the engine runs it produces water vapor. Unless the oil is thoroughly heated to operating temperature to drive the moisture out, the water vapor condenses, mixes with various acidic compounds also made by a running engine, and corrodes the guttyworks pretty badly.

Fully applies to cars etc. engines as well, even running till the coolant temp hits normal is not good enough as the oil temp on cars probably takes 10/15 mins longer to reach full operating temp. needed as shrike mentions. Get out & drive for 1/2hr +

[Stoney]

SNJ tips from Walt Ohlrich
On shutdown
set 1000 rpm
prop back for 60 seconds, cleans plugs
cut mixture
count the blades to check compression, if # goes up, compression goes down
don't move throttle, its set for the next start
don't turn off fuel to keep the cork wet

[Matt Gunsch]

Ken,
that is a great way to get a induction fire, when you pump the throttle you are sending jets of fuel into the blower case, but most if it is coming back down into the carb and airbox where it will pool, if the engine sneezes thru the induction, your carb and airbox will ignite. For a hot start you can try cranking with the mixture in idle cut off and move to rich as it fires, or give it 1/2 to 1 shot of prime, if possible while cranking. It is better to get the fuel into the cylinders than into the blower on starting.

Careful Matt, there's a Warning in section II of the -1 against priming a hot engine because of the possibility of fire. Regarding the backfire, it only happens if the throttle it open too much. This hot start technique is the best I've found in 28 years with the T-6, it's as easy as starting your car. Now if anyone has a good way to hot start an IO-550 Bonanza I'd really like to hear it, that one makes my palms sweat!

Ken

A backfire comes out the exhaust, a sneeze is thru the induction, as far as priming a hot engine, I said to use 1 or even 1/2 a shot of prime and I would rather have fuel in the cylinder than the airbox.

As far as the 550, I have never had trouble, full throttle, full rich, hit the boost till you see a fuel pressure rise as you are trying to do is purge the vapor from the lines, throttle and mixture back, crank the engine, when it fires, bring in the mixture, if needed, use a bit more boost.

If all else fails, flood it and do a normal flooded start, full throttle, mixture in cut off, crank engine, as it fires, reverse the throttle and mixture.

[Dave Hadfield]

I was at the hangar at Gatineau yesterday and saw this...



It's a bit misleading. We don't fly in the winter. This run-up was done post Annual Inspection. And the aircraft came out of a heated hangar.

But in general, it's normal up here once the temps go below about 10C (50F) to pre-heat the oil. And it's best if you can heat the whole engine too. This is my set-up on the Fairchild. It uses a hair-drier which blows onto the oil tank attached to the firewall. A half-hour of this and you don't have to idle so long after start, and the plugs foul less.



As for the T-6, yes, it's normal here during cool starts in spring and fall to leave a full charge in the primer before you crank it, and if it starts then dies, you feed that it to catch it. If you don't need it, no problem, you just squirt it in gently at a higher idle and the engine hardly notices it.

Dave

[Matt Gunsch]

Dave,
That looks cold, and just for that, I am going to go ride my Goldwing.

[spencerat6]

I agree with Dave I've been flying my T-6D for almost 40 years and if it's been sitting in the hanger for a while I always keep a full charge in the primer when cranking. Bob

[Ken Dwelle]

Matt/Taigh-

Thanks for the feedback, it's good to examine techniques and assumptions regardless of how they have worked in the past. I'll try a different way.

Ken

[Michel Lemieux]

Dave...it looks like your Fairchild has a cold and has a thermometer stuck up its nose

Do not know anything about cold weather starting....but now I do understand it can be costly if not done right!!!!!!

Michel

[Matt Gunsch]

I had all the cold weather starting I care for when we brought the C-119 and A-26 down from Greybull. Both were so cold the engines were frozen solid, we had to heat the C-119 first and start it before we could move the heaters to the Invader.

[Ken]

I was doing Rich's technique but with the mixture rich. For hot starts, I've been doing as Ken D says, but moving the throttle only while turning, as Taigh says.

I will have to see if I can scan the individual pages, but the USAF Skyraider student notes from 1971 has a nice discussion on back fire vs. after-fire. Back fire being a excessively lean mixture barking out the induction system before the intake valve closes and after-fire being excess fuel igniting in the exhaust. During the cold starts, looking back, I did not always use enough shots of prime - is it possible some cylinders were over-rich, while some were too lean to fire? I did see some after-fire while doing so but the engine would not continue to run and died.

Ken