Help - No idle

[M Towsley]

Re: Help - No idle

You have received good info but let me comment on something in your original post. You state you go out and start it from time to time. That is a very bad thing to do. Combustion's byproduct is water. If you do not get the engine/oil up to temp and for quite awhile you are coating all those expensive internal parts in water, as well as the same for the oil. It would be better to either fly it or pickle it. And turning the prop doesn't do anything but wipe eight off whatever oil you have on those expensive metal parts. Good luck on the idle issue, mine had a very minute piece of junk which affected the lowest idle circuit, killing my engine while on final.

[clear_prop1961]

Re: Help - No idle

What is the adjustment on the idle mixture needle? Could it be close? Should be about 1 1/2 to 2 turns out I believe as a starting point.
Jerry

[Guest]

Re: Help - No idle

I agree that carb port isn't flowing, but I since we have been through the carb twice especially paying attention to those ports, I can't happen to think of some sort of vacuum leak at low RPM not pulling the fuel in.

Bowl vent? Please clarify. Other than the needle seat, and throttle butterfly, the carb was completely disassembled to the best of my knowledge.

My experience is that vacuum leaks cause a crappy idle not no idle.

But often one can find a vacuum leak by running the engine a slow as possible and spraying carb cleaner or ether on the vacuum parts.

The engine speed will increase when you spray a leaky part.

Not all carb cleaners will cause the engine speed to increase so test first by spraying into the carb inlet, if that does not work you may have to use ether.

Dave R

[3Dreaming]

Re: Help - No idle

I know of others who have had carbs apart before and missed something that was causing an idle problem. Make sure you remove all screws and flush all passages with carb cleaner. You can start by removing the idle screw and cleaning with carb cleaner before removing the carb again.

I had another A-65 that didn't want to idle well. The Champion spark plugs excessive resistance, and wouldn't even fire correctly on a bomb tester. A new set of plugs fixed the problem. Based on that a thorough inspection of the sparkplugs might be in order.

[Mark Julicher]

Re: Help - No idle

Perhaps the float used to have a soldered-on counter balance weight that has fallen off? That would starve the engine at low power settings.

[N95334]

Re: Help - No idle

I would suspect the primer or primer line.

[astjp2]

Re: Help - No idle

I have a spare carb that I can swap on, that helps determine if its the carb or something else. If its the carb, just send it out, home repairs are dangerous if you are not a mechanic without the right tools. I have a lot tools and a few to the stromberg carbs but I dont mess with the Marvels, I just send them back to spruce who sends them to Volare/Tempest.

I just worked on a PA12 that had a 200° high EGT, wound up being a primer line separating from the ferrule.
Tim

[Robert Lees]

Re: Help - No idle

Part of my 50/100/Annual inspections is to get someone to pump the primer while I look at the pipe connections...particularly on small Continentals at the spider.
It is not unknown for the soldered joints to fail, giving rise to fuel leaks upon priming, and air leaks upon running.

Rob

[hisoos]

Re: Help - No idle

I'm finally back. With tail between my legs. It has been the daughter's birthday for the past three weekends so I haven't had time to get out to the hangar. Not to mention, more bad luck. Ended up having to send my 182 prop in for an overhaul.

Anyway back to the T-craft. Convinced it wasn't the carb, (it was), I replaced intake gaskets, thoroughly cleaned plugs (not many hours on them), eliminated primer, then finally back to carb after taking a looooonger look at the schematics.

Found my problem. The idle tube.

Even though I had it out once before, I was fooled (by not looking at the schematics at the same time), by the larger holes which all seemed clean and clear. However on try 3 after doing everything else, the teenie weenie hole at the bottom that feeds the whole idle system was clogged.

Threw it back together and she fired on the first pull after three priming strokes. Idle was a little low, still tweaking that, but fast and slow taxied a fair amount, without issue.

Gave the old bird a good sponge bath tonight to make up for my stupidity.

One good thing came out of all of this other than fixing my idle problem, some good TLC was done to the intake and ignition system along the way. Thanks for everyone's contributions. I hope mine helps some other would be fool out there some day.

[Robert Lees]

Re: Help - No idle

I always clean ALL the parts in an ultrasonic cleaner. Rob