difficulty starting O200

Henning said:
Most times I see blue stains in air boxes, people have been pumping the throttle without turning over the engine, trying to prime with the accelerator pump. It's effective if you let the fuel sit in the box for a minute and fill the induction tubes with good vapor, only problem is it occasionally starts the plane on fire. Many primer systems squirt the fuel at the intake valve.
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BS alert. air boxes leak. the fuel doesn't stay there. fuel in the cowling, yep, that's where ya want it. :)
 
nrpetersen said:
On colder starts I've had good luck hand propping with a dead closed throttle & mixture rich, but going very easy on the prime. The idle jet will flow fuel into the carb at a high velocity point for the airflow plus there will be a momentary reduction of pressure in the intake manifold that will assist getting any manifold based liquid fuel to flash into vapor, which makes it combustible.

MoGas helps. Be sure the magneto switch works on every shutdown and prop as though the mags are live anyway.
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That is exactly what I was taught many many years ago.
 
nrpetersen said:
On colder starts I've had good luck hand propping with a dead closed throttle & mixture rich, but going very easy on the prime. The idle jet will flow fuel into the carb at a high velocity point for the airflow plus there will be a momentary reduction of pressure in the intake manifold that will assist getting any manifold based liquid fuel to flash into vapor, which makes it combustible.



MoGas helps. Be sure the magneto switch works on every shutdown and prop as though the mags are live anyway.
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Same here.


Jim R
Collierville, TN

N7155H--1946 Piper J-3 Cub
N3368K--1946 Globe GC-1B Swift
N4WJ--1994 Van's RV-4
 
Dan Thomas said:
Lycomings do that, and I see blue stains on Lycoming airboxes too. Priming is one of those things taught by instructors that have no clue what's going on inside that cowling.

Dan
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Yep, Lycoming carbs work the same as Continental (since they are the same :lol:). Pump the throttle and fill the box. The flight school I used had a renter start a 172 on fire that way.:rolleyes2: Luckily it was near the office and someone ran out with an extinguisher in time to prevent any major damage, just had to change the nose tire.
 
Henning said:
Yep, Lycoming carbs work the same as Continental (since they are the same :lol:). Pump the throttle and fill the box. The flight school I used had a renter start a 172 on fire that way.:rolleyes2: Luckily it was near the office and someone ran out with an extinguisher in time to prevent any major damage, just had to change the nose tire.
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And as you said, the fuel will stay in the carb airbox.. so how could it burn the tire?
 
I remember reading something last year that talked about not using the accelerator pump with a stopped engine to avoid fuel pooling in the air box, and pausing between priming (on aircraft equipped with a primer) and cranking to give the fuel a chance to evaporate. These seemed reasonable and intuitive to me. OTOH, the 162 POH says to pump the throttle and then crank. :dunno:

IIRC, the sequence of events on Sunday was something like:
1. Three pumps of the throttle, crank.
2. No joy. Weird. Repeat step 1. Still no joy.
3. Crap, did I flood it? WOT, idle cut off, crank, no joy.
4. Crank while pumping throttle, no joy.
5. Go inside before you kill the battery.

The engine is <1000 since new.

Henning said:
The underlying disease is typically low compression, this gets exasperated by low temps. You were just under primed is all. It helps to crank the engine as you prime.
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It is either fuel, air or spark. My best guess from you have said, is that it is spark issue. Is it difficult to start when the engine is warm? The fact that it use to start fine for you per the POH procedure means something has changed.
 
Similar conditions today. I was the second person to fly, so the engine was already warm. Just for variety, I tried cranking while giving it throttle (as opposed to POH procedure of pump then crank), and it started right up. I'll have to try that again.

FWIW, the FBO was using starting fluid, not straight ether. Upon inquiry, it didn't sound like they had to resort to using it very often.
 
Similar conditions today. I was the first person to fly the aircraft, so it was cold. The airplane behaved similarly to post #1. It would fire when I pumped but did not catch initially, but I kept on cranking, and kept on pumping, and it eventually caught. I had to pump it more than I anticipated and I had to open the throttle further than I anticipated.

So, Henning was right (not enough gas) and Tom was right (pump while cranking).

I think the real lesson is that one must be patient.
 
GeorgeC said:
Similar conditions today. I was the first person to fly the aircraft, so it was cold. The airplane behaved similarly to post #1. It would fire when I pumped but did not catch initially, but I kept on cranking, and kept on pumping, and it eventually caught. I had to pump it more than I anticipated and I had to open the throttle further than I anticipated.

So, Henning was right (not enough gas) and Tom was right (pump while cranking).

I think the real lesson is that one must be patient.
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Next time you have the first start of the day, try this.

Open throttle 1/2"
Pull primer out, wait until it fills.
Mags to both
Start cranking, while slowly pushing the primer in. when it starts, adjust RPM to 800-900, allow it to warm up, prior to dropping to idle, and leaning.

OOPS, I forgot this aircraft has no primer.
Do not cycle the throttle too fast, that will not allow the accelerator pump to deliver all of its fuel.
push it 1,2,3,4, pull it closed, push it 1,2,3,4.
 
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Tried the four count between cycles, no joy. More vigor is required if this engine is to achieve a happy ending.
 
Our O-300 started having the same issue. Impulse coupling in the mag came apart. We were at 750 hrs since rebuild on the mags on the recommended 500 hr interval. After mag overhaul, it went right back to starting in 2-3 blades.

Joe
 
dentonf250 said:
Our O-300 started having the same issue. Impulse coupling in the mag came apart. We were at 750 hrs since rebuild on the mags on the recommended 500 hr interval. After mag overhaul, it went right back to starting in 2-3 blades.

Joe
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Why didn't it start as easy on the other mag.?
 
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