Weak glow plugs

**RknRusty** Sun Dec 18, 2011 10:51 pm

I installed a glow plug that glowed brightly in an engine that I had used blue Permatex thread locker for the tank screws (not the one I carefully built last night, letting the thread locker set, this was a quick job I did today). Being the impatient guy that I am, I slapped it straight onto the test 2x4 and cranked it up. It ran out the tank and wouldn't start again. I removed the head and plugged in the battery and there was no glow. It had a bright glow before I installed it. Hmmm, Permatex? I took a syringe full of alcohol and blasted the coil, dried it, and hooked up the battery. And whaddya know, red hot. It cranked and ran fine for 4 more tanks.

Okay then, I have a few more that won't glow, so I gathered them up and cleaned them the same way and they all lit perfectly, even the old W filament that I thought was dead years ago. Some were relatively new and some were decades old. Under the magnifying glass, one of the newer ones had a pink glob that looked the color of Glowplugboy fuel. None of the rest looked contaminated, a couple were less than shiny.

For the life of me and my electronic engineering background, I cannot explain what may have been coating them that was conductive enough to short circuit the coils(except the one that was touching the side of its enclosure). But the moral of the story is, shoot your plugs with denatured alcohol occasionally whether they need it or not.

John Goddard Mon Dec 19, 2011 10:51 am

I haven't got any Meths (denatured) Rusty but I've got some single malts around my office
do you reckon it's worth a try?
J

**RknRusty** Mon Dec 19, 2011 10:55 am

John Goddard wrote:I haven't got any Meths (denatured) Rusty but I've got some single malts around my office
do you reckon it's worth a try?
J

You might want to distill it first.

John Goddard Mon Dec 19, 2011 11:02 am

RknRusty wrote:
John Goddard wrote:I haven't got any Meths (denatured) Rusty but I've got some single malts around my office
do you reckon it's worth a try?
J
You might want to distill it first.

Unfortunately I'd feel compelled to drink it then.

Very Happy

andrew Mon Dec 19, 2011 12:10 pm

RknRusty wrote:I took a syringe full of alcohol and blasted the coil, dried it, and hooked up the battery. And whaddya know, red hot. It cranked and ran fine for 4 more tanks.

...............Under the magnifying glass, one of the newer ones had a pink glob that looked the color of Glowplugboy fuel. None of the rest looked contaminated, a couple were less than shiny.

That's an interesting result.

Over the last few years, I've been flying almost exclusively (please don't string me up for this) NORVELs. There was a lot of discussion (some has shown up here) on the use of rubber fuel bulbs or syringes with black rubber seals and the contamination of glowplug elements. On some of my high time engines, while the plug still heated and functioned, close examination of the elements showed a deposit that looked almost like white fur growing out of the element. Since some of these engines had been fueled only with an all nylon syringe, I assumed that the deposit was from some other contaminant.

I never thought of using alcohol or acetone to try to clean it. It certainly will be worth experimenting with a couple of solvents to see if I can remove it -- I can't help but think that a clean element should improve running. Some of you with a better chemistry background may be able to explain it, but it is my understanding that ignition is due to catalytic action and that plug heat only serves to accelerate the reaction. If that's the case, then anything that coats the element would tend to block or slow down ignition.

**RknRusty** Mon Dec 19, 2011 12:28 pm

My son the Chemist will be home this coming weekend. I'll ask him about it. And the best cleaning method. Meanwhile, here's some interesting info about the stuff of which our plugs are made:
http://www.periodicvideos.com/videos/078.htm

PV Pilot Mon Dec 19, 2011 12:46 pm

I used Hydrofluoric acid to clean a old supposedly dead, no-glow standard plug. the thing lit up nice and bright and I ran the old 1952 motor with it. Don't know how old the plug was, but it would not light when I tried intitally.

microflitedude Mon Dec 19, 2011 12:59 pm

If I think a head is dead, I make sure the element is centered and is broken before doing something to it. Smile

I have had one go out, it was broken in the middle of the coil.

Good idea with cleaning them.

**RknRusty** Mon Dec 19, 2011 2:35 pm

If you use acid it probably etches the platinum a little bit. And you'd need to neutralize it if you aren't going to use it in a few minutes. I'll have to ask my chemist what to use for that. Sodium hydroxide maybe, but I forgot how to make it. I'll have those answers this weekend.

tubebass Mon Dec 19, 2011 3:02 pm

Years ago we got a batch of fuel that was killing plugs. They would still glow but the engines would not run. Switching to different fuel didn't help till we changed the glow plug. We figure the elements got coated with some foreign substance.

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