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Hard starting

Yen

Well Known Member
I have a carburetted D2G O320 Lycoming in my RV4 and while it has never been really hard to start it always takes two attempts.
There is no primer for this engine and the throttle is connected to an accelerator pump.
Cold starts, by which I mean down to about 10 degrees C up to 25 deg. I give a few pumps of the throttle, 2 to 5, then with only L mag on I run the starter and no matter wether I pump more or not at all it will not start. Stop the starter, wait 10 seconds and it will then start within 2 or 3 revs. Throttle cracked about 6 to 12mm.
I have tried running the starter, then pumping. Same as before. Trying to start without priming doesn't work.
I am just wondering what I am doing wrong.
Hot starts are dead easy, fuel on, throttle cracked, left mag and away she goes.
 
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Try waiting longer between the first prime and first start attempt. This will give the fuel more time to vaporize in the induction tubes.
 
Yen, you may be cracking the throttle too much. I used to hand prop a Super Cub and if you move the prop and don't hear a "whoosh" sucking sound at the air intake, it's cracked too much and the air doesn't have enough velocity to carry the fuel up hill.

Best,
 
Try with the throttle fully closed. My reasoning is that the low pressure in the manifold promotes vaporisation of the trapped fuel. It works for me.

I believe there is an 'idle enrichment circuit' (whatever that is) that kicks in when the throttle is near closed, perhaps this is disabled at 6-12mm open. My guess is cracked means 1-2mm.
 
THIS IS A GOOD WAY TO CAUSE AN INDUCTION FIRE.

To amplify on this, pumping the throttle without cranking the starter on this type of engine does nothign but create a puddle of gas in the air box. Dangerous, and it does nothing to help you start. (I think it is a practice taught by people who used to do it on cars with downdraft carbs - but it wherever it came from, it is useless on a Lycoming).

Try hitting the starter, THEN give a couple of throttle strokes WHILE CRNKING, finishing with the throttle cracked. If you have good spark, it shoudl light right off.
 
To amplify on this, pumping the throttle without cranking the starter on this type of engine does nothign but create a puddle of gas in the air box. Dangerous, and it does nothing to help you start. (I think it is a practice taught by people who used to do it on cars with downdraft carbs - but it wherever it came from, it is useless on a Lycoming).

Try hitting the starter, THEN give a couple of throttle strokes WHILE CRNKING, finishing with the throttle cracked. If you have good spark, it shoudl light right off.

Agree with Paul. A fellow instructor had this occur in a Warrior. A backfire (undetected) lit and burned the induction scat tubing. The debris clogged the intake, but only after being airborne and inside the marine layer clouds. Fortunately, he was able to reverse course. They couldn't make the airport, but landed unscathed in a field.

Use the accelerator pump only while cranking. It doesn't help that many checklists say to pump the throttle, and then five or six steps later it says "Engage Starter". Yikes!

Don
 
I too have to crank a lot on a cold (more like hasn't flown today) start than I am used to. I have no primer on a O-360 with dual electronic ignition and the skytec starter spins it pretty fast. It generally starts at the end of the 3rd try of 5-6 seconds of cranking, if it's been flown that day it starts on a couple of blades.

I had an induction fire while trying to start a C-150 without preheat at 30 degrees and am very cautious about pumping the throttle without the prop turning. I found that 2 quick pumps of the throttle immediately followed by hitting the starter yielded quicker than only pumping the throttle with the prop turning. This is very consistent from well below freezing to 100 degrees.

I will try closing the throttle completely, I always crack the throttle about 1/4 inch.
 
I too have to crank a lot on a cold (more like hasn't flown today) start than I am used to. I have no primer on a O-360 with dual electronic ignition and the skytec starter spins it pretty fast. It generally starts at the end of the 3rd try of 5-6 seconds of cranking, if it's been flown that day it starts on a couple of blades.

I had an induction fire while trying to start a C-150 without preheat at 30 degrees and am very cautious about pumping the throttle without the prop turning. I found that 2 quick pumps of the throttle immediately followed by hitting the starter yielded quicker than only pumping the throttle with the prop turning. This is very consistent from well below freezing to 100 degrees.

I will try closing the throttle completely, I always crack the throttle about 1/4 inch.

Yes, definitely try closing the throttle more or all the way. You may consider installing a priming system. I would not own a carbureted aircraft without one, way too much risk of an induction fire.
 
I installed the Vans primer system and only plumbed it to 2 cylinders (1 and 2 I think). While I was building I read a lot of stories about how it's not really needed, etc. Those stories almost had me convinced it wasn't necessary, but now I'm glad I have it.

I have a high time O-320 on my 9A right now (new Titan O-340 on the way) and the only problem I've ever had starting was when I used the primer before starting an already warm engine after a fuel stop. Now that I've learned only to prime this engine when cold, a 2-second primer shot consistently yields starts within 1-2 seconds of engaging the starter. Warm starts are no issue either - no primer, mixture rich, crack throttle open, and it fires right up.

I've seen an induction fire that started from fuel pooling in a Skyhawk air box. It destroyed the plane. My two-cylinder primer setup from Vans works quite well, and really wasn't bad to install.
 
Thanks all of you.
I had a good start today, gave 2 pumps of the throttle while crankng, then closed the throttle and away she went. Nice temp for starting about 25 deg C or 77 deg F
 
I've also had good luck since I started closing the throttle completely. The last 2 cold starts (50's F) I've hit the starter, given the throttle 2 quick pumps and throttle all the way back. Seems to light off the first try after 4 seconds of cranking, kinda different to start and then advance to throttle from 500 RPM's.
 
Good comments all around for this topic. I will repeat though... my coment about pre heat. As fall approaches, I see this topic come up again and again.
As owners of experimental aircraft, we have some options that make equipment simpler to install. The EZ heat (or other automotive brand) oil pan heaters are one of the simplest solutions. If owners have a hangar, they probably have AC power, they can get the engine warm before start. If condensation is a concern, then simple devices like the Switchbox are available. A simple text message gets the heater going.
Any way you look at it.... as winter approaches... a warm engine starts easier and lasts longer.
 
I installed a pan heater a couple of weeks ago. It will bring the oil temp up to 110 degrees. I also had problems getting the accelerator pump method to work with any consistency and if the engine is cold it's hit or miss whether I can get it going. I got Tom at T S Flightlines to build a primer line setup for me (great guy to deal with BTW) I haven't hooked it up yet, but I'm expecting it will make a difference.
 
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