Engine won't Idle.

[mohawktipi]

I have a Continental C-85-12F with a stromberg carb. It runs great at 1400 rpms or higher but will not idle. I've tried adjusting the idle/mixture needle valve in and out but it does not seem to have any effect. Any suggestions?

[Robert Lees]

Re: Engine won't Idle.

Idle jets blocked?

[mohawktipi]

Re: Engine won't Idle.

Is there any way to test the idle jets without taking the carb off? If I remove the idle/mixture needle valve and spray Berryman's B-12 into the opening, do you think that will clear any soft obstuction? The engine has not been run in a while. I removed the strainer plug and checked the screen. No contaminats there. Engine runs smooth at 1400 rpms or higher but if you tap the throttle a little to go below 1400 the engine sputters and dies. The idle throttle stop screw is all the way in so it cannot be adjusted for higher idle speed.

[Ragwing nut]

Re: Engine won't Idle.

Check your intake hoses

[Forrest Barber]

Re: Engine won't Idle.

If intakes check out then Pull carb apart the little idle bypass suction tube has a bug in it.... unscrew it and blow bug out. Order new gasket kit, maybe a new needle valve and seat too!
Boil it OR use immersion in carb cleaner , find someone to do it or send it in if not familiar with carbs.

[astjp2]

Re: Engine won't Idle.

Did you adjust the idle air screw? If it is closed, you wont get any air so it wont run. Tim

[Carrieve]

Re: Engine won't Idle.

Forest is right. Mine just did that same thing and there was some foreign critter living in the bottom of the idle tube. Huffing and puffing from the outside won't do any good. It is a very simple carb, but check the needle and seat. I use to teach this stuff years ago and this is Model A technology.

[gfortin]

Re: Engine won't Idle.

Forrest gave you the exaxt instructions that my A&P,AI gave me. You won't believe the difference. It will get over the hump better when you push throttle in. Good luck

[Guest]

Re: Engine won't Idle.

I think this helps keep bugs out but can't prove it; I always pull carb heat on when I park so its harder for most bugs to get up there.

Dave

[Forrest Barber]

Re: Engine won't Idle.

I was told by my Dad that this is the same "mud dabber" that gets into the pitot system too....

[mohawktipi]

Re: Engine won't Idle.

Think we found the problem with the failure to idle. When the the intake elbows were attached to the cylinders, the wrong gaskets were used. Although the holes aligned properly, they were the wrong shape. This allowed air to get into the cylinders. I never checked the gaskets when we re-assembled the engine because cylinders were rebuilt by a Department of the Navy engineer. Once I get everything back together, I'll report.

[Hank Jarrett]

Re: Engine won't Idle.

Having once been an engineer for NAVAIR (under the Dept of the Navy) I can tell you where you work doesn't make you infallible! When we turn wrenches, we are all mechanics, and can all make mistakes. This is one for me to tuck away for future reference. Hard to see the problem when you pull it apart and it looks like an undamaged, new gasket!
Congrats on figuring out a really sneaky problem.
Hank

[mohawktipi]

Re: Engine won't Idle.

Problem solved. Engine runs like a champ, I mean Tcraft.