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Hagerty Employee

How spark plugs work and what they can tell you about your engine | DIY | Hagerty Media

The humble spark plug is well over a century old, but its technology and function have remained unchanged. Learning how a spark plug works and what it can tell you about your engine is critical, even in the age of highly intelligent, computer-controlled engines.
Intermediate Driver

I found this an extremely helpful video for most people so that they can understand what it is to look for if they are doing there own vehicle tune ups.
For myself, I am going to send a copy of this article to some of my customers to help them better understand what I have been trying to explain to them when they are needed for their aircraft. Granted, the plugs are different between cars and an aircraft engine, but it helps to explain what it is I am seeing when I tell a customer needs new plugs or possibly a new or rebuilt cylinder for their aircraft, which is far from being a cheap repair should the cylinder require changing or repairs. Aircraft plugs are usually either massive electrodes or fine wire plugs and unlike an automotive plug are quite expensive, with say, a massive electrode that has dual grounding points running 25 to 50 bucks per copy or a fine wire plug, which actually lasts longer, but is incrementally more expensive at around 100 bucks per copy, and when you look at most, but not all piston driven aircraft the run to 4 cylinder, 6 cylinder and 8 cylinder with some engines using up to 12 or in the case of radial engines, up to 18 cylinders, and to many if not most aircraft owners cost is always an issue. The symptoms talked about in the video are pretty much the same however, and that is the most important part. I have found many times that owners are fouling their plugs because at start up, warm up and preflight checks of their engines, they are running with the enrichment lever at full rich, instead of leaning out the fuel mixture accordingly. Of course, at start up, setting power for take off and doing their pre takeoff checks, they will be at full rich, but when idling at the end of the runway waiting for takeoff, or taxiing the aircraft, it is actually much better to lean out the mixture to keep from fouling their plugs. But for trouble shooting an engine that just doesn't seem to make as much power as it should, or even backfire when advancing or retarding the power or cylinder misfires, the first thing to look at is the plugs and usually, with a temperature gun, you can tell which cylinder is "misbehaving" by noting that the temperature is cooler than the rest of the cylinders. I'm sure I'm boring most of you now, but you get the gist of how important knowing what to find when looking at spark plugs and what to start with as the "usual suspect".
The biggest thing I always remind my customers of, is the plain fact, ( no pun intended ), that with a car, you can pull over to the side of a road. With an aircraft, you cannot pull over to the side of the cloud...

As always, Kyle--Excellent presentation--and so clear! Thank you for taking time to work through this presentation. jay salser
New Driver

This is a very informative article.