In 3 years of PA28 ownership and approx 300 hours use I have pulled and cleaned the plugs out at least 8 times during Annuals and 50 hour checks.
Apart from picking little lead balls out from the bottom plugs & cleaning and gapping, I’ve only ever seen perfect colour grey plugs.
So some questions,
(a) can an over rich 2 1/4 hour flight cause seriously fouled plugs and
(b) if I had never noticed this issue, would have one normal flight after the “carbon deposits” then cleared the plugs and left them the normal colour?
Archer-181 wrote:
Then, last week, I had to abort a flight due to mis-firing during power checks
It doesn’t take hours. I’d suggest that the plugs fouled between start up and run up on that particular day. Make sure to lean the engine for taxi, to the point where the mixture is almost at idle cutoff.
Plugs can get “fouled” by oil, lead, carbon (soot) and dirt.
Typically, overly rich mixture tends to wash the oil off the cylinder walls and it’s that mixture that fouls the plugs.
If the problem persists, I would have that cylinder(s) borescoped to be sure you don’t have a broken piston ring or other cylinder problem.
To answer your questions : Yes, plugs can get fouled in just an hour or two; and light fouling often clears itself through running the engine at max revs and/or agressive leaning.
Thanks Silvaire. It didn’t happen between start up and run up that day as it immediately was missing on Cylinder 2 on start. I’ve been leaning on taxi for a few months now which I think is good advice as apart from fouling issues, it is more difficult to ignite a lean mixture so highlights any ignition problems.
Also thanks Michael. I am pulling a few plugs out after every flight, so far so good. I also have the “Mike Busch” recommended Borescope on the way to me from the U.S. (See other thread on Borescope). I’ll be having a look so I can play with my new toy!
If I am not mistaken the Archer has a very similar O360 engine as I have in the Mooney.
Plug fouling doesn’t need hours, all it needs is a few minutes of ground ops in full rich. Our procedure for starting and after landing is to pull the mixture immediately out about 4 cm and leave it there. The mixture goes to rich only before the power test and then again before take off.
I’ve had several flights aborted due to this issue when one of the pilots did not lean particularly after landing.
There is a burn off procedure for the Mooney which sometimes works. If a magneto runs rough due to fouling, go back to both, reduce power to 800 rpm and let it run for a minute. Then increase power gradually to 2200 rpm and in this position run another magneto check. This is supposed to burn off the carbon deposits from the plugs. I’ve had it work and I’ve had it fail when there was just too much.
Since we practice leaning vigorously on the ground, we have not had a reoccurrance.
Thanks for that Mooney_Driver. It’s amazing how I got away with this for so long!
I have never leaned on landing and I had a 3-4 minute (landing) taxi on the flight before the trouble stated. The debris checking vehicle was on the first exit which meant I had to go the long way round! Perhaps that was it as I’m normally off at the first exit.
Thanks all, and also thanks to Peter again for such an excellent forum
I flew a PA28-160 for about 300 hours and it would foul quickly on the ground while taxiing at larger airports. This type of fouling would typically clear during run up (leaned and maybe increased to 2000 rpm for a minute or two).
I also once flew for about 1.5 to 2.0 hours on a flight from Canada to the USA. You are supposed to meet the customs people within a window of zero plus 30 minutes or so. As a result of a massive tailwind, I was going to be early, so I throttled waaaay back. Can’t recall, but perhaps to minimum power (e.g. 40-50 percent power).
On the next start, the plugs were super fouled. I didn’t have tools to remove and clean the plugs, so ended up running the engine at a fairly high RPM (leaned) for a longer period. The plugs eventually cleared, but after that I considered packing the appropriate tools when travelling away from base.
After these incidents I always lean (almost to cut-off) on the ground before and after landing. Just remember to enrichen the mixture before advancing the throttle for take-off, otherwise it might stall (don’t ask me how I know :-). If you aren’t able to lean after landing, you can always run the engine at a higher rpm prior to shut down (say 1800 rpm) for 20-30 seconds to clean the plugs. I think there is even a lycomming procedure for this.
One thing is fouled plugs. However if the plugs get fouled, there is a chance that you will some day get a stuck valve due to carbon deposits on the valve stem which prevents the valve from moving through the guide.
So keep leaning!
With my Piper Warrior (PA-28-151, O-320-E3D) the plugs will foul even on a small airfield on the way to the runway if not leaned properly, and properly means to pull back the mixer way back! Once one of the plugs is fould it can take minutes to burn off the deposites.
I somehow wonder how those flight school planes where most of the time people are still told they will die a horrible death if they come near the mixture knob survive this kind of misuse…..
