O200A no start

[8261]

John, to answer the prop question:

Since I hand prop, I consider what I called "normal resistance" when the blades stop after a single rotation and return to the 10/4 o'clock position (also with coupling clicks) for the next swing.

The first day it wouldn't start, it would spin..say 2 or 3 rotations...not returning to 10/4...and also no audible coupling clicks.

[6643]

The first day it wouldn't start, it would spin..say 2 or 3 rotations...not returning to 10/4...and also no audible coupling clicks.

That's very puzzling. The only way I can think that would happen is if the plugs were out. No resistance means no compression. That still doesn't explain no snapping from the impulse couplings, unless you managed to spin it over 200 RPM.

[8261]

Hmmm. Interesting. I’ll be back at it tomorrow and let you know

[8261]

Today’s update...pulled the mags. Re-installed following johns suggestion.

Tested top leads for spark with R mag on. #1 fired with couplings released at 7’oclock position. Next blade #3, next # 2, next #4.

L mag on. Same for bottom plugs. Same results. All good sparks in correct order.

Put it all back together. Normal startup...nothing...ahhh

[6643]

All good sparks in correct order.

Forget about the o'clock stuff, and the order. You need to confirm that #1 is at TDC on the compression stroke when the #1 plugs are sparking. Keep in mind there are two TDC positions for #1, but only every other one is the right firing position. (The other is the top of the exhaust stroke.)

[5099]

This subject has gone beyond unbelievable! There is nothing more basic then the ignition system of the old Continental engine. Here is a basic way to check out your magneto timing to your engine.
First, remove one spark plug from each cylinder. (this is to reduce compression resistance during prop pull thru and safety of an unwanted firing).
Second, connect one spark plug to the number one cylinder lead from either magneto and lay the plug on the surface of the cylinder. (the need here is to make sure you have a good ground for the plug).
Third, put your finger over the spark plug hole of number one cylinder. (Remember, the cylinder number is cast into the crankcase next to the corresponding cylinder).
Forth, with the mag switch in the “both” position, rotate the propeller, by hand, in the proper direction. You should feel a “push of air” from number one cylinder. Watch the spark plug for number one cylinder. When it sparks, stop and look at the timing mark on the crankshaft flange. (Remember, you should be looking at the Bottom of the crankshaft flange) Make note of the degrees shown on the crankshaft flange in relation to the Crankcase halve seam.
If you don’t get a spark at the time I’ve described then you have a mag timing problem or maybe an internal mag timing problem.
There is nothing more basic them the ignition system of any aircraft engine. That’s why they are so dependable. Engine engineers can make their design “fool proof” But, they can’t make it “mechanic proof”. STOP, take a deep breath and think about the mechanics of how things work.
JMHO, Steve

[6643]

When it sparks, stop and look at the timing mark on the crankshaft flange.

Right. the "0" on the crankshaft should be very close to the lower crankcase seam. (Your impulse couplings should have a 25 degree lag.)

[6298]

If the prop is in the right position for propping, the blade will be just behind the T/C mark on the flange (7 o’clock). John, Steve and I have described the timing procedures the same with different wording. It’s hard to imagine that Christopher timed it wrong, if you read his initial posts. Fuel, spark and compression are the three ingredients for running. I have been thinking fuel might be the missing ingredient. An engine that has started on the second stroke for many hours and went to 20 strokes is a puzzle. The broken primer line is curious. The Marvel carburetor has a accelerator pump. When cold, I start mine with two throttle pumps and it starts right up.
There are four filter screens in the system. Each tank has one where the fuel goes to the fuel valve, the gascolater has one and there is a screen in the carburetor. You can check the first three with a flow test. The fuel line should flow steady and fill a gallon jug in about a minute.

[6643]

I have been thinking fuel might be the missing ingredient.

Don't forget his claim of "no resistance" when turning the prop. It doesn't fit with his other symptoms, though.

[8261]

Well I do have an answer...

Yes, the Timing was right all along. Phew, I got that one down forever.

I get it to turn over 2nd blade. 5 min run up, put it thru rpms. Slight miss in higher range.

Long story short—it starts three times straight 2nd blade, but I’m not happy with static rpm, slight miss, and slow/even 150 rpm mag drop from both fresh mags.

I take it for one run down strip and not producing normal power/acceleration.

Park it, feel cylinders. Too hot to touch #1,2,4. Luke warm #3.

Pull #3 rocker cover. Stuck exhaust valve.

Unfortunately I oversighted this #3 cyl, but live & learn.

Thanks to those hanging around for problem solving! I’ve posted long for anyone out there in my shoes..for those that would’ve diagnosed in 5 min, then

Chris