GP testing, multimeter setting
 

OK, Ive replaced Glow plugs many times before but never have I been certain that Ive had the correct setting on my meter.
I need it really dummed down. A properly functions GP will read .8 to 1.2 right? but on what setting on the meter?
What setting should the meter be on? The options are 2000k, 200k, 20k, 2000, 200.

200. Then touch the meter probes together, and it will read something like 0.2 Then measure each glowplug (preferably with harness connected) Subtract the value you got touching the probes together. That's it.

I think good ones can be lower than .8.

Keep in mind that sometimes the plugs will seem to have the proper resistance (that's what your measuring here) when in actuality they need to be replaced.

When I replaced my plugs recently they all tested good, but with the new plugs starting was much more smooth.

Fresh battery in meter. Meter set at 200 reads .5 with leads touching each other.
Meter set on 200, relay unplugged, touching one lead to tip of GP threads and other lead to top of valve cover I get consistant readings across all plugs of about 97.5. Checking against other potential good ground points in engine bay gets same readings.
Could they all go bad at once? Last replaced at 221K in Jan/05. Car at 336k now. This thing started like a trooper all winter without a block heater. Only started giving trouble a couple days after I installed a heat exchanger and went to a high ratio veggie oil blend right before a cold snap. Now with 3 hours on block heater its still a no go.
Not to get too off topic but IF I am reading the plugs correctly it would suggest that the veggie may have built up a bunch of carbon on my plugs to crash em. Viable theory?

I would think the resistance would be unaffected by carbon build-up.

Chances are one or two plugs haven't been good for a while and now the rest are giving out. That's what I would think, anyway.

Looking at your post again, you do a lot of driving! Wow!

The resistance won't be directly affected by carbon, but carbon build-up may insulate the tips from the prechambers, causing excessive heating within. That could indeed severly shorten their life.

Make sure you unplug the (5 pin) connector from the relay to the GPs when you test the individual GPs. If not, you will not be measuring the actual resistance through each GP. I normally measure the resistance from the connector to ground for each GP, should be in the .5 to 1.0 ohm range (there are very small numbers on the plastic connector). Normally they will just read infinity (open circuit) when they fail. When you detect a bad GP, check again at the GP connector to make sure it's not a broken wire. I doubt that any carbon build-up will affect the electrical resistance.

oops I meant 221K to 236K (not 336) 15,000 miles on these plugs in 15 months.
I have heard that a couple bad can take out others. Its strange though how all have the same ohm reading at 97.
Pin connector was unplugged for testing. I tested at the end of the plug itself. Ill test at the pin connector to see if it results in any different readings.

This pictorial will show you how to test them with your meter.

http://dieselgiant.com/glowplugrepair.htm

Angst, you know of a diesel MB indy in the Chattanooga area? Thanks, Doug