O-540 Engine trouble

[vontresc]

So I am trying to chase down some engine issues on our O-540-J3C5D in the 182RG.

The complaint I got was from another pilot that the engine ran rough during the landing at low power settings. High power settings seemed fine. So I test flew it and indeed at full rich and at 12-13"MP it was running rough. Leaning the mixture slightly seemed to help.

So I decided to run the three in flight tests that Mike Bush suggests (https://resources.savvyaviation.com/in-flight-diagnostics/), and I am in need of help in interpreting the "Induction Leak" check.

Here's the flight data
https://apps.savvyaviation.com/flights/5220954/8d8ee70b-2754-451b-9be8-72b3d42e901a

26:00-28:00 In flight Mag Check leaned out
33:00-42:00 GAMI Lean test
42:00-51:00 Induction test

The induction test says to run the engine at a high power setting at full rich, and then compare the EGTs when the engine is running at a low MP. The interesting thing is that 1,3,5 all rise in EGT, and 2,4,6 all drop in EGT.

I need to look at the intake runners in the daylight, but there is a marked difference between the right and left side of the engine. Mu money is on the even cylinders having an induction leak, but the drop in EGT has me scratching my head as I'd assume you'd get a rise in EGT if it were over lean

 

[Mtns2Skies]

The complaint I got was from another pilot that the engine ran rough during the landing at low power settings.

Most importantly... *Which* other pilot, and how would you rate their competence? I've seen what your club puts out .

 

[EdFred]

Shots fired!

What about the carb. I had rough running at low power, turned out to be a carb rebuild.

 

[vontresc]

The one you are thinking about, but it is a legit issue I verified yesterday ;-)

 

[455 Bravo Uniform]

Not saying you do or don’t have an induction leak, nor do I know the Busch test exactly, but if you go lean of peak, your EGTs start to head back down. Maybe a massive air leak?

 

[Dan Thomas]

The J3C5D has a six-way manifold immediately ahead of the carb. Looks like this, cast into the oil sump:



The carb goes on the hole with the four studs. Horizontal draft carb, HA-6. If there's an induction leak it should affect one cylinder real bad, the others on that same side a bit, maybe, the others not much at all. Note that the right front induction riser, for #3 cylinder (part #4 in the picture) comes off the bottom of the manifold, as does the #6 riser (#7 in the pic). If that carb isn't atomizing well, fuel puddles in the bottom of that manifold at low power settings and those two cylinders suck it up and flood out and it runs horribly. Been there, dealt with it. Fresh Lyc overhauled engine, too, with an overhauled carb. Carb was covered under warranty but I had an $8K bill in the interim for just the replacement carb. The next carb fixed it. That price is from 14 or 15 years ago.

Now, that engine, in that airplane, has a really rich mixture at full rich. I complained to Precision Airmotive about it, since they built the carbs, and they told me that this was the way Lycoming wanted it. Super rich. So I told the instructors to observe the POH and lean it whenever they had to, which was much of the time. Lean it for runup or your mag drops will be bad. Lean it on downwind when you pull the carb heat or it will be rough and maybe want to quit on final someday. Lean it in the climb, especially above 5K, to get it smooth and so it's not leaving black smoke behind it. After that we had no trouble.

Edited: had the bottom right riser feeding the #5 cylinder. It actually feeds #3 (middle right). Pulling the sparkplugs should show fouling of the plugs on #3 and #6 if the carb isn't atomizing right.

 

[Captain Sweet T]

Is it turbo? If it's a turbo, it will run rough at low power settings and full rich.

 

[Clip4]

I flew a 182RG for 20 years. The engine is prone to run rough at low power settings in summer when it’s hot due to too rich mixture.

Here are some things I would check.

The carb heat box to determine you don’t have an issue there.

Check for a broken primer line.


The intakes flanges coming out of the oil sump. Sometimes those come loose. They are field repairable and you can rent the tool to replace a bad one. An of course the gaskets at the cylinders.

The other thing I would do is a pre takeoff runup, fly the plane for at least 30 minutes so you can totally heat soak the duel mag, land and do another runup. The blocks in the mags can have micro cracks and break down when hot.