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Carburetor questions

E

Eddie747

Registered User
About done everything I know to do except a new carb to the O-235-C1B and still hard to start unless warmed up, starts just fine if its been running and warmed up.

Will start with throttle opened halfway, but just not getting gas flowing with normal 1/4 inch opened. Carb guy said its ok if running normally after it starts.. but something is not right. I dont want to spend $800 on a carb if it wont fix the problem but everything else has been replaced, new left mag with impulse coupling, new plugs, primer is working right. Carb guy says its just not getting the air/gas flowing so open throttle and start it that way as long as it runs correct after it starts, I'm not happy with that answer. It runs normal after its starts.

Anyone experience these symptoms?
 
Primer working ok? But if it requires half throttle to start that sounds like it's already flooded?

Glenn
 
Yes primer is working well, three cylinders and all 3 have just been cleaned and tested and spraying good.
 
If I dont use half throttle it will eventually start after cranking priming cranking more priming more it finally starts but barely runs, about 200 -300 rpm, guessing didnt look at tach but hits all cylinders and not missing just barely running, have to gas it to get up to normal idle and than it is fine, its done this every cold start for the last 2 months.. about 10 times, so its the new norm, prop barely swinging fast enough to keep engine running than about 15 -20 seconds it will finally rev up to normal idle rpm on its own, immediately if I give it a lot of throttle, than it runs normal.

After it gets to the normal running you can bring throttle to idle and it is the normal 650 rpm, not the low barely faster than starter speed it does initially, thats something I have never seen, the prop just lobing along barely running for about 20 seconds and than comes up to normal idle.
 
Last edited:
No, no backfiring at all. Compression are good, and runs fine once it gets going. I will look for an induction leak, I haven't thought about that.
 
Eddie, It has been a long time since I have operated an 0-235. I'm seeming to recall that they require a lot of prime to get started. It could help if after you prime, you leave the primer out and then push it in while the engine is turning. This ensures that the fuel gets sucked into the cylinders rather than running back down the intake tubes. Then if necessary after it starts but before it gets spooled up you can continue to add prime.
 
Seems to me these engines do not suck fuel out of the main jet while cranking with throttle cracked, so you are depending on prime.

Try this: Crank, and while cranking pump the throttle twice between idle and full. Most that I fly start instantly that way without prime.

The little Continentals need fuel too, when cold, and get enough with throttle at idle after four or five blades.

My recent experience does not include really cold weather, where even more fuel is required!
 
I had a IO360 that was hard starting...almost impossible to hot start...i called a old guy that worked on fuel injections systems. He gave me a number of tests to do on the fuel system and everything was fine. I called him and told him what all I did and he replied "it's the mag".
I had the mags checked and the impulse mag was weak...started great after rebuilding mag.
 
Three pumps and a slightly cracked throttle started any O-235 I've been around - temperature be damned

My mechanic has been on a kick of taking carbs apart recently. I was a little defensive because my plane ran great. Seems he had seen some real junk. Before he started my annual we went through the logs. No mention of it being rebuilt during the last overhaul. We had to go back twenty years to find where it had been apart.
The Gizmo inside that controls mixture was heavily corroded.
 
My 2 cents... have you checjed the idle mixture setting? It sounds lean to me. If so, it'll probably idle OK when warm, but it'll be too lean when cold. If nothing else, back it out 1/2 turn and see if the situation improves.
 
PerryB said:
My 2 cents... have you checjed the idle mixture setting? It sounds lean to me. If so, it'll probably idle OK when warm, but it'll be too lean when cold. If nothing else, back it out 1/2 turn and see if the situation improves.
Click to expand...

Yes idle mixture is ok, we adjusted that and it is set to give a 50 rpm rise as you pull the mixture out to cutoff from 650rpm idle

Going to take the carb off and have it looked at, it has been on for decades.. heck I have no idea when it was last apart and cleaned, might be as bad as the post above and corroded inside.
 
Had same symptoms on O360 this year after rebuild. Sent carb out, no help, no induction leaks, verified timing. Slick Mags were freshly overhauled. Swapped out the impulse mag and boom, started righty up. Since that rebuild I’d had some problems with CHT’s. Rebuild shop said they don’t know how but EGap was way off and impulse barely firing. CHTs were from that advanced EGap.... and it would pass run up. Good luck.


Sent from my iPhone using SuperCub.Org
 
Slick mags are notorious for causing strange starting problems usually E gap related. They seem to come out with a service bulletin every other year saying they got a bad batch of points.
DENNY
 
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