Testing old style glow plugs, Help Please! - PeachParts Mercedes-Benz Forum

NC240D76 · #1 10-25-2004, 09:30 PM

This is in a 115 body 76 240d with the old pull knob to activate the glow plugs not the system using the key and a relay/timer.

With winter coming on I thought it would be a good idea to make sure the glow plugs are up to par.
I searched here and found you can test them with an ohm meter or remove them and hit them with twelve volts just long enough to see if the element glows. Well, my meter seems to be in hiding along with various other tools so I decided to remove the gp's and test, and just in case Murphy is hanging around I decided to start with the parts car.
No big deal getting the glow plugs loose and out even with the mosquitos helping.
I put the first glow plug in the vise (gently of course) and attached the postive lead on a 6 amp battery charger to the tip and the ground to the body where it would ground to the engine. I could hear the battery charger hum but nothing from the element.
Well, when I was removing the glow plug I had noticed the strange method they were wired and the fact that the jumper to the second gp came from the collar not the body of the gp so I carefully attached the ground there but the element would barely start to get hot before the charger kicked off because it thought it was shorted to ground (which I guess it sort of was).
So I grabbed an old battery that I thought should have some charge left in it and made some jumpers out of some 10 awg, well as soon as I touched the jumpers to the tip and the collar of the gp the tip flamed up and burned off ending up about three feet away from the table the vise is mounted on.

I had sprayed some triflon (teflon based lube spray) on the threads of the glow plugs to help remove them and some could have gotten on the element but I assumed the system ran off 12 volts. Was the gp bad or did I just piss away another ten dollar bill?
I think I would like a little advice before I continue, Help!

What am I missing?