Sounds like the meter is not perfect. Or it's battery is low. Still good enough for your test though. It could be intermitent leads or oxidized plugs but think not as the given values are pretty close.
Anyways consider the oscillation as a meter problem for practical purposes. You are looking for low values on each plug. Usually a burnt out plug will be wide open. You still might notice a plug with increased resistance . The oscillation range should vary if there but at slightly higher values when it settles down.
As you say not rocket science but confusing to some exrent depending on amount of experience using a meter. Usually the worst problem reading things is getting good clean connections with no oxidation on your points of contact.

If you touch the probes together you should get a steady zero, or close to it. Do you by chance have it set on voltage? That'll give you funny readings if there's no voltage. Also if you meter doesn't auto-range, make sure you have it on the right range...you're only measuring 1 Ohm. Just for fun, get a light bulb and put one lead on the metal tip and the other lead on the threads, that'll give you some resistance.

If you can get your hands down by a plug, but one probe on the back end where the wire connects, and the other probe on the engine block (anything big and metal on the car can be a ground) or on the body of the plug. That will directly measure the resistance across the plug.

Then check the wires, one probe on each end of the glow plug wire.

Good luck

__________________
1985 300TD-euro 352,000 mi
1974 240D (1?)52,000 mi - has a new home now

............the digital multi-meter strikes another innocent victim.........yet again.

If I ever decide to buy one of them..........please shoot me.

Carlton, you use an analog one? I just bought this POS on Saturday from Radio Shack so I'll just go return it, no big deal. When I put the leads together they jump between .1 and .3 for about 10 seconds, then zero out. Should it just always be at zero, no questions asked?

It measured the battery fine at 12.73 volts, so I'm thinking the meter should be ok....but when I'm on Ohms at the "200" dial mark--which is where the Haynes manual says to go, and where it is on Diesel Giant's tutorial on glow plugs--I can't seem to get the ground situation sorted out. I touched the negative lead all over the engine metal, various bolts, etc., and got no reading on the glow plug ports.

Anyway, I'll give it a shot with the jerry rigged piece of wire connecting to the negative battery terminal tomorrow.

The car cranks like a bastard and barely turns over after sitting for a cold night. Something's up.

Again, what tools do you guys use to remove the actual glow plugs?

How often do you have to replace glow plugs living in a relatively cold climate?

Thanks

__________________
JBG
1985 TD wagon, 228k
running on grease since 3.07
AUSTIN, TEXAS

I have a $10 Radio Shack analog meter (cigrarette pack size) that does 99% of my troubleshooting. It cannot measure 1 ohm, so I use the $50 analog meter for that. The $50. meter gets used once every two years.........if that.

I don't comment on the function of digital meters. Too many folks have gotten way too confused by their displays and their questionable accuracy and repeatability. This might be due to the fact that they are low cost meters.........

An actual wrench is needed for actual glow plugs. You can remove imaginary glow plugs with anything you like. When I am in hurry, I just call Snow White and have her send over five of her best dwarfs.

Can I get her number? I could have used a couple dwarfs on Sunday. I asked my 5 year old to trade hands, but he said NO.

__________________
1987 300TD 309, xxx 2.8.2014 10,000 mile OCI


Be careful of the toes you step on today, as they may be connected to the ass you have to kiss tomorrow. anonymous

“Be who you are and say what you feel, because those who mind don’t matter, and those who matter won’t mind.” Dr. Seuss

tangofox, can I just call you and have you come over? That'd be as good as 5 dwarfs, easy.

__________________
JBG
1985 TD wagon, 228k
running on grease since 3.07
AUSTIN, TEXAS

My $3 Harbor Freight multi-meter does just fine. I typically test the plugs right at the plug itself to rule out any harness problems.
I don't see the point of grounding at the battery. You're testing the resistance of the plug so I would think it's better to ground to the engine block since that is what the plug is grounded to. Why introduce the variable of the engine ground strap into the equation?

I use fantastic gear wrenches to remove my dream glow plugs and actual gear wrenches to remove actual glow plugs. If things get really tough I reach in my toolbox for the Platonic Form of Gear Wrenchness.

__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

Isn't it hard to rule out a harness problem if you omit the harness from the test?