Preventative Maintenance......Plug wires/Plugs


Well-Known Member
Jul 15, 2010
Fayetteville, AR / USA
My fishing trip was OK. Not the best, not the worst. We caught about 50 fish in two days of hard fishing. Weather wasn't too bad. Usually we would have caught 50-75 per day, but that's fine, it was a good time all round until......

We got in the plane to head home. My first clue that something wasn't quite right was when the engine died during my first start attempt. Hmmm.....that's unusual. My second clue was when I had to use the primer to keep it going even though it was warm outside. That's odd....must be fouled plugs.....but I did my usual lean burn the crap off the plugs before what the heck.

200 rpm mag drop on the right mag....three attempts at clearing the plugs and no dice. Rough as a cob and getting worse...CRAP!! Luckily there is an A&P on the field. All plugs test good...mag is removed and tests good...two cold cylinders.

Final diagnosis is the plug wires. One is shot, several are intermittent. CRAP, CRAP, TRIPLE CRAP:mad2::mad2:.

It's Friday afternoon, the shop is closed on Sat. and Sun., I have oddball Bendix mags, and you can't just go down to Nappa and get a set of plug wires for a 1958 C172. Plus I have cooler full of fish fillets that need to get to the freezer 500 miles away. There is a NO Saints/LSU bowl game double header and every freaking rental car is spoken for...except Some ginormous GMC Yukon. So I get to drive a gas guzzling thing the size of school bus home. $%#@#%$%#$%^%$ These are some expensive fish.

The parts just got there this Friday, a week later, plane is still 500 miles away. Now I have to see if this really fixes the problem and if so find a way down to retrieve the AC.

I keep the airplane in the hanger with a heater on a thermostat to keep the engine warm. That prevents condensation and keeps everything nice and dry. Because of this, the plug wires were probably marginal, but tested OK at annual. It was cold when we landed, and got colder. The airplane was parked on the ramp. Then we had a warm front with humid air, and several 100% humidity mornings. I'm sure the engine was dripping wet, and water would have been in every crevice or flaw. So any weak point in the plug wires became a short circuit waiting to happen. Once a path to ground is formed....Ugh...

The thing that really gripes me is for the cost of all this inconvenience, I could have replaced all the plugs, wires, and had the mags rebuilt or changed to slick mags.

So how often do you guys replace your plugs/plug wires as a preventative thing? Would you do the Slick mag conversion?