My citabria is having trouble with the mag checks. I believe it is plug fouling. If I run it up and lean it out for a few seconds it will typically clear up and the mag check will pass but I would prefer I did not have to do that. The engine is a lycoming 0-320 with a constant speed prop. I know the plugs are gapped to the correct setting and recently cleaned.

What are my options for fixing this?

Michael

I would try setting the mixture to "one millimeter" short of killing the engine for all ground operations (maybe, two millimeters <g>).

If you lean for ground operations, just remember to BE CERTAIN to go full rich for takeoff.

First, I'd clean the plugs. If you are getting a mag drop, it's because one or more of the plugs is fouled. Pull them out, and try to figure out which plug is fouled. If it's just one, you may have gotten lucky, and just caught a clinker that was left in a cylinder the last time they were cleaned, and it happened to land in one plug.

Now, go to Lycoming's web site, and do a search for the Lycoming recommended engine shut down procedure. This has been around forever, yet I find NOBODY uses it. It is specifically designed to help prevent plug fouling during shutdown, and it works.

If on the other hand, it's all the bottom plugs (and it will normally be the bottom plugs) then you may want to consider other options.

If this turns out to be a continual problem, I'd consider switching the bottom plugs to REM 37 BY plugs. These are the massive electrode plugs designed specifically for the lead fouling champ of the world: The Cessna 152 engine.

I'm betting you just got a clinker in one plug, and once you get it out of there, you'll be fine.

Do use the Lycoming shut down procedure, however, cause that's specifically what it's designed to prevent.

MTV

I'm not sure if it will apply to your situation or not but w/ my cont. o-300 during the warm months i can really easily put to much full in the cylinders on start up even w/out priming. Then after i taxi out and do my mag check the bottom plugs run like hell until the excess fuel burns off. I think they are more flooded than fouled.

Mike


Is your 0320 a 150 or 160 HP motor?

flyer

I cleaned the spark plugs out about 4 flight hours ago and I had the same problem before and after. I have been leaning aggressively at every chance I get but it is not helping too much. It seems the only way to clear the plugs so it will pass the mag check is leaned out full rpm operation. I will try adjusting the mixture screw tonight.

I have the 150 HP model.

I have been following lycomings engine shut down procedure I found in their "Lycoming Flyer Key Operaton" manual. There are actually quite a few interesting things in there.

Mike

I lean for ground ops, but I lean it so much that it won't run at all past 1/2 throttle or so. At low power settings you can't hurt anything no matter how lean it is. I learned to do this after taking off one time when I looked down to reduce power only to see the mix knob was already out
I've learned that if it can be done, then it's only a matter of time before I do it.
You can tell which plug by letting it run on the "bad" mag imedately after start up. Let it run for a short while at low speed say 1000 to 1200 or so, then shut it down. Your problem child will be the cold cyl. / exhaust.

Mike

The 0320 150hp motor was designed to run on 80/87 octane fuel. If you are using 100LL, it has about 3 times as much lead as 80/87. When I had an 0-320 150hp motor, I ran only regular auto fuel. I never had any fouling problem. The plugs were always clean because of no lead. I never leaned aggressively. The engine ran perfectly.

Good luck

flyer

I have all the mechanical prowess of a labrador, but if you are having the same problems before and after cleaning the plugs, perhaps it's not lead buildup which is causing the problem?

I ran my O-320-E2D on mogas for 16 years and don't remember fouling the plugs. If you have the STC, consider a mixture of 100LL and mogas to get the lead down. I run my O-360-CIF from the moment it cranks so lean that advancing the throttle past 1/3 open will kill the engine. It stays that way until run-up. After run-up, if I am in line for take off, it goes super lean again. As "a64pilot" says, it won't run at all past 1/2 throttle.... Mine will not make it to 1/2 throttle. - Mike

Jr.CubBuilder wrote:Could I be your mag harness?

Dude, that sounds perverted.

It could be the "P" lead or the mag or a cracked insulator on the plug etc. Isolate it to a particular cylinder, swap the plug top to bottom. If problem goes with the plug, toss it. If the problem doesn't move with the plug, then you can at least rule out plugs. If it's not a bad plug then I bet the "P" lead.
If it is lead fouling then MTV had the answer, at least in my book; Y plugs or fine wire if you can afford them.

MIKE MIKE

The 0360CIF also runs very well on auto gas. The STC requires the premium grade, however, because of the higher compression.

flyer

Thanks, "Flyer", I have the STC and just yesterday topped the tanks off with mogas. I had the folks in Moultrie install the STC right after they did the pre-purchase/annual inspection. - Mike