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Carb issue.. maybe?

I pulled it through with the #1 harness end sitting against the cylinder, after I had set the mags and before I put the spark plug back from locating TDC.

Did not fire at all while cranking and I could hear the impulse click while doing so... I did make the mistake of pushing the mixture in (I should have left it cut and will do that next time I try to start). Still thinking the fuel nozzle / fuel level may still be too high and if I leave the mixture cut maybe it will start tomorrow.

I gave it one shot of prime.. then a second one later on. I prime all 4 cylinders... have for 17 years and always have used 3 shots for start. Subsequent cranking after the initial attempt was with mixture cut and still had fuel dripping out the box. Turning the engine backwards had more drops hitting the bucket. Tomorrow I will also remove all the primer lines and make sure none are clogged as well as pull the nozzle fittings to check, clean and reinstall.

Like I said, I've always had a hard time starting with no preheat.. but figured with things set, impulse working, it should have fired on a 10F day.. No.

I'll change the settings on the video..
 
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That looks like a decent spark. Though I prefer to see a "bluer" color. The only (that I am aware of) fix for this is a stronger magnet. Magnetism can be gradually lost over long periods of time. It now appears that the mixture may be too rich. Perhaps the fuel is not atomizing properly from the primer nozzles? I'm running out of ideas. Are you using 100LL or auto-gas?

I have had similar troubles in cold weather. The fuel just can not vaporize enough to ignite. A weak spark needs help and you have corrected that.
 
I would check the integrity of your intake system and if you can't find anything, replace the carb. Years ago I overhauled an engine for a guy. He called me back that winter and said he wore out a starter cause the engine wouldn't start cold below 30 deg. I took him a different carb (overhauled just like the first) and a new starter and he never had a bit of trouble again. Sometimes you're can't find the little thing that's causing it .
 
That looks like a decent spark. Though I prefer to see a "bluer" color. The only (that I am aware of) fix for this is a stronger magnet. Magnetism can be gradually lost over long periods of time. It now appears that the mixture may be too rich. Perhaps the fuel is not atomizing properly from the primer nozzles? I'm running out of ideas. Are you using 100LL or auto-gas?

I have had similar troubles in cold weather. The fuel just can not vaporize enough to ignite. A weak spark needs help and you have corrected that.

The left impulse had a nice blue snapping spark... just couldn't video it as easy as the right one. And the right did go bluish if I rotated a little harder.

Maybe I have a plug that won't fire cold... I'll keep sorting it out. Like I said I'm going to pull all the primer nozzles and first check the plugs before I do anything to them... then clean, gap, recheck under pressure etc and reinstall.
 
I would check the integrity of your intake system and if you can't find anything, replace the carb. Years ago I overhauled an engine for a guy. He called me back that winter and said he wore out a starter cause the engine wouldn't start cold below 30 deg. I took him a different carb (overhauled just like the first) and a new starter and he never had a bit of trouble again. Sometimes you're can't find the little thing that's causing it .

Intake system should be fine, ran like a dream all summer but you never know. Do you now if I can throw a 10-5135 on there in place of the 10-3678-32. I seem to remember it was a C-172 carb, but can't find a cross reference for it anywhere.
 
I had a problem similar to this. Got cold, flip and flip that prop (J3), fuel pouring out the carb. Checked timing, primer, cleaned plugs, swapped carbs. Finally switched from car gas to avgas and that was the ticket. Started right up. Seems that, for me as I can't speak for others, that the car gas fuel was just not vaporizing right and the plane was really hard to start. Once it did start, and the cylinders were warm, it had no issues, but stone cold, it liked the avgas only to start. I know this makes no sense as there is nothing wrong with running car gas in an engine and I do it all summer with a little bit of avgas mixed in, but for me, straight avgas seemed to be the cure.I don't know if this is your issue, but skywagon was also wondering what fuel you are using.
 
Intake system should be fine, ran like a dream all summer but you never know. Do you now if I can throw a 10-5135 on there in place of the 10-3678-32. I seem to remember it was a C-172 carb, but can't find a cross reference for it anywhere.

If you are out of ideas and have it on the shelf, put it on and try it.
 
I run AV gas only in mine. 100LL from day one.

....out into the cold I go. -18C this morning. And if plugs and primer aren't it, I'll try that -5135 carb
 
Wayne sometimes when it's below freezing and it doesn't start and gets rich it will frost the plugs and it won't fire till you pull and dry them, just like an old snogo.

Glenn
 
Glenn, It usually pops a little first, enough to warm the surface of the plug just enough to get a drop of moisture across the plug gap, then freezes that drop shorting the plug. Wayne says that he isn't getting any pop at all.
 
We had an 0320 Pa12 a couple winters ago and we came out from breakfast and he just cranked and cranked and it never fired. His primer didn't work so we pulled a plug to pour in some fuel to prime it. The plug was frosty, we pulled the top plugs and warmed them up and it started right up.

Glenn
 
In for lunch... and to warm my damn toes! Checked all the plugs before doing anything to them.. again in the hangar.. in the cold with my Vixen plug cleaner / tester. ALL plugs fire fine under pressure up to 90 psi. Cleaned them all, checked / set the gaps.. retest and played with point gaps until they all fire on both points evenly at pressure.

I then put them back in with new gaskets rotating top to bottom on each cylinder, like I always do, and hooked the harnesses back up. Figured everything was again cold (about -14C) so I tried to start it leaving the mixture cut.... two shots of prime. No hint of fire... what so ever. Gave it another shot of prime and cranked, again nothing. Minor fuel drippage on the floor, but not near as much as when I had the mixture in full yesterday.

Pulled the primer nozzles, as I couldn't remember what was in there and I have 3 "wand" and 1 flush face spray nozzle. It's not just a wide open 1/8 x 1/8 NPT fitting like I've found in other homebuilt engines. ALL of them seem to blow through... and I currently have them soaking in cleaner just to make sure they are all the same when I put them back. When they do go back, shortly, I will swap out the flush nozzle for a 4th wand style... but don't suspect this is going to get me running without a preheat.

I would think this rules out the carb as the item not making it start... or one would think anyhow, although I'm still suspect of the excess fuel pool..
 

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Do not do this without a competent throttle handler in the cockpit! After priming place throttle in wide open position in order to draw in only air while cranking. This will help to keep from drawing in too much fuel. Then try a start. If it starts it will be at full power. When the throttle is closed or cracked it will draw fuel while cranking.

Also/or you could only prime while/and after the starter is turning the engine as this will pull the fuel into the cylinders instead of letting it run back.
 
That's how I did it earlier SW... Primed during the crank. Back out I go... I'll put the nozzles back in and some cowling back together so my nose bowls not hitting the prop and try the full throttle with it tied to the Kubota.

Now if it starts that way.. .are we back to suspecting an overfilled carb bowl ?! :smile:
 
Did you say that you have a new style light weight high rpm starter? The original (non reduction gear) direct drive starters in cold weather often couldn't turn the engine over fast enough to start. Even with a good battery.
 
Yes.. I have a Skytec starter.. the original PM they came out with. It never cranked real fast on the Gill battery... but it sure does on the Odyessy, I could water taxi on the thing cranking. Why I was concerned that this high speed cranking was sucking fuel out of the carb AND not allowing the impulse coupling to do it's job.

I also hate reading mystery novels..... I cleaned the primer nozzles.. soaked and poked and they flow a little better when blowing through them. Put them back in.. again left the mixture cut and tried to start by giving a shot.. then another shot while cranking. Absolutely NO hint of firing. Tired the full throttle gig... again.. no hint of firing.

Started to second guess myself.. as I had a guy appear at my hangar door yesterday (that I didn't know) just as I was finishing up setting the mags. The left would blink the odd time and I thought I had a loose connection using a couple spare P leads in the Bendixs'... and I also started to think "I didn't time these things on the intake stroke"..

So NO.. timed on compression.. dead on 25 BTC. BUT... I hooked the buzz box up direct to the key terminals and made another little video. Notice the left mag blink... as I go from when they come on at 25 to a little closer towards TDC.


At this point I figured I had nothing to lose and at least wanted to know if it starts heated. Threw a moving blanket over the engine, tucked it in and plugged in my 900 W heater... for about 40 minutes. Went back out.. unwrapped... hit the key with no prime.. no throttle.. mixture cut and it fired right up within a blade. Mixture in and it ran smooth... shut down about 20 times and it will fire everytime at one click of the impulse.

I'm baffled... time for some El Dorada Silver Deluxe!

Concerned with the left mag "blink"... guess I'll wait for those new points and put a set in the left mag and set everything again, and then button her back up. AND CARRY MY PREHEAT UNIT EVERYWHERE! ;-)
 
Wonder if the blink is a little defect on my mag point follower cam?.. that's allowing the points to close again and then open.

I keep telling the wife we need to move to AZ or TX... and just fly back and forth to our island camp in Temagami for the summer. Then I could just leave the amphibs on and throw away the heater!

Just can't believe that so little heat is allowing something to work... and I can't figure out what that something is...
 
Irish, We'll hold a place for you here on the runway. It'll start here, 67F today. You've spent enough time trying to make that thing obey that you could have moved here by now. ;-)
 
Wonder if the blink is a little defect on my mag point follower cam?.. that's allowing the points to close again and then open....

Check if there is any side play in the cam. This could indicate worn bearings which could cause the points to blink the light.
 
Will do... like I said I'm going to at least redo the left when the points arrive next week, hopefully. I'm thinking that open.. close.. open might be interrupting the coil "collapse" and messing with the spark.
 
Wayne sometimes when it's below freezing and it doesn't start and gets rich it will frost the plugs and it won't fire till you pull and dry them, just like an old snogo.

Glenn

Funny thing about that. In forty years of flying Ive never had a frosted plugs. one of my students called and said she couldnt get my PA-11 to start. It fired briefly and quit and nothing they could do would get it to fire again. Finally after an hour of trying , I told her to put it away and try it the next day. fired up on the first try the next day. Frosted plugs is the only thing I can come up with.
 
BTW... finally found a carb chart (Kelly Aerospace) that shows the 10-5135 carb. It appears to be used on many O-320 models, apparently interchangeable with the 10-3678-32 and 10-5009. So in the next round of trials and tribulations... if I can't get it to cold start I think I'll throw the O/H'd 10-5135 that I have here on and see what happens. Worst case, even if it doesn't fix the cold start, I could get my rear cylinder EGT's to match the front ones. They've always run about 100 to 150F hotter than the fronts.
 
BTW... Worst case, even if it doesn't fix the cold start, I could get my rear cylinder EGT's to match the front ones. They've always run about 100 to 150F hotter than the fronts.

It's time to install baffle ramps up to the center of the front cylinders.
 
My CHT's are all pretty close... rears maybe 25 F higher than fronts in all flight regimes, but cruise through climb they all generally running between 325 and 420.

It's the EGT that the rear are generally 100 to 120, sometimes 150, higher than the fronts. Seems to be a common thing on a narrow deck of rears running hotter / leaner and I've read some of that is caused by the -32 carb as well. Who knows..

My baffle ramps are almost dead center on the fronts... only file picture I had handy.. you can see the silicon line of where they sit.
 

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I misread your post. You did say EGT, I was thinking CHT. The different temperature on the EGT is not important. In fact you do not care what that number is. You want to watch at what point in relation to each other that they arrive at peak while leaning. The closer together those numbers are, the closer the mixtures are between the cylinders. A carburetor system, due to it's design, has different flow patterns between the carb and each cyl which varies the mixtures between cyls. The only time that they would be close is when the throttle butterfly is wide open. At and above about 6,000 feet in cruise. When the butterfly is partially open the fuel/air mixture is swirled between the butterfly and the distributor in the sump. This causes different mixtures to go to each cylinder. In a fuel injected engine the fuel is mixed with the air at the cylinder intake valve giving a more consistent mixture. Thus the EGTs will be closer together.

Clarification: you want the EGTs to arrive at the peak point as close to the same time in relation to the mixture control position as possible. This means that the mixtures between the cylinders are close to each other. With a carb this is unlikely to be close.
 
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What I always thought and have been flying it for many, many years with the cylinders reading that way. I put a new exhaust on 2 years back and made sure each EGT probe was exactly the same distance below the flange, as the old exhaust they were a little off. Made no difference in readings.

While going through all this carb stuff I read one of Fobjobs posts... about polishing the carb.. ramping the venturi and getting more even fuel distribution and more even cylinder EGT temps. I just be happy with a cold start right now.. .tried it again a little while ago (-18C last night but currently -8C) and again a no go and fuel on the floor.

Still can't decide whether to swap carbs while I have the cowling still torn off, or to just throw a new point assembly in the left and preheat and try to get some ski flying in!
 
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What I always thought and have been flying it for many, many years with the cylinders reading that way. I put a new exhaust on 2 years back and made sure each EGT probe was exactly the same distance below the flange, as the old exhaust they were a little off. Made no difference in readings.

While going through all this carb stuff I read one of Fatjobs posts... about polishing the carb.. ramping the venturi and getting more even fuel distribution and more even cylinder EGT temps. I just be happy with a cold start right now.. .tried it again a little while ago (-18C last night but currently -8C) and again a no go and fuel on the floor.

Still can't decide whether to swap carbs while I have the cowling still torn off, or to just throw a new point assembly in the left and preheat and try to get some ski flying in!

If you pull a top plug is it wet?

Glenn
 
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