I checked the glow plugs at the relay with a test light they all light up,i also changed the relay with a known good one from my wagon,car still doesnt turn over,it just goes waga wa ga wa ga waga but no spark,glow plug light is on.
Help please.

First, we need your help. What year and model W123? Is it a 240D or a 300D? What year? There are different glow plug systems in the various years. Tell us that and we may be able to help.

__________________

"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970

Are you sure it is your glow plugs or relay?
It could be a number of other things, I'm guessing your starter is fine if it is trying to turn the engine over?
I'm prety sure diesels don't spark they combust.

Please fill out the car info in your signature to get better replies. Also if the engine is spinning too slowly, it will not start. From what you posted, the engine does, in fact, turn over, it just wont start. Is that correct?

__________________
81 300CD (sold) 1972 280 SEL 4.5 (sold) 1966 250 S 4 spd (sold) 1974 450 SL (sold) 86 BMW 325ES (sold), 1973 280C (sold) 1988 300 SE.

battery fully charged? i was sure my battery was fully charged when it wouldn't start, but after overnight on the charger it started right up.

__________________
1980 300D (non-turbo, 421k miles)
1984 300TD (turbo, 305k miles)
1985 Vanagon (170k miles)

Its on a w123 82 300d,I removed and changed all glow plugs with nice lightly used Bosch glow plugs,every one of them glowed very hot when i hooked them up t a battery,positive on thread and body of plug to ground,i then reinstalled fuel lines and purged it of any air twice by loosening andre tightening the lines twice,i did notice very little diesel flows out or maybe thats how it is,battwery is running very low voltage so im going to charge it tomorrow and try again,the funniest thing ias after i reinstalled the glow plugs the light came on a few times while trying to start but later died and now no glow plug light,engine turns over and car wants to start5 but still acts as if it had bad glow plug,i even installed a relay from another 300td and srtill no go.'Help please.

Begin by checking the glow plugs for voltage when you turn the key to the glow position.

__________________
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

I have an ohm meter at which setting should i tes them,2k,200 or what?

Basicly the multimeter is set to a number you think you will hit 0.0, 00.0, 000.0 etc I would choose the 00.0 for the multimeter not sure which that one is but all you need is the 12 volts displayed.