Symptom of 1 or 2 bad glowplugs...
 

Last week when I started the car (300D) on cold mornings, it started fine but ran rough for about 30 seconds. Then, a few days later, it was very difficult to start when cold. I metered the GP's and found two bad ones. I'm sure it was just one at first, causing the rough running on start up. Then, with two bad, it was just too much to expect it to start cold. I found the Bosch 80006 GP's at Autozone for $9.99 each and replaced them all. Starts perfectly now.

The bad ones were #4 and #5. # 5 is a PITA to get to. Four is only a little better. The others weren't too bad. Took a couple of hours the first time. Next time I will remove the injector lines and get a ratcheting 12mm wrench. I think that will cut my time to less than an hour.

just pick up a 10mm and 12mm wratcheting wrench and youll be fine on the 617s. it makes the job soo much easier. for the 603s i changed out all 6 GPs w a 1/4in wratchet, 6in extension, universal joint and a 10mm and 12mm socket. no need to remove the intake or any injector lines. youll have a much easier time w those tools and youll do the job in half the time :dancefool

Agree:
 

Three sets in a month.
I remove the injector lines (17 MM ratchet wrench), remove the glow plug wires (8 MM ratchet wrench), remove and replace the glow plug (12 MM ratchet wrench)

Eh, our 83 started fine with only two working plugs down to about 20 degs, then below that it would start....just took looots and lots of cranking. :D Replaced them all, and it starts at virtually any temp almost instantly now. (extremely healthy engine, oil analysis proved this)

I've done it both ways........injector lines in place........and injector lines removed.

Considering the fact that the injector lines can be removed in five minutes or less, I cannot understand why anyone would attempt to change even one glow plug with the lines in place.

The fear of a leak or a failure to get the lines back on properly can be overcome after one session of R & R.

I agree that the gear wrench makes it much quicker and easier.

i agree
 

totally. lines off always for me.

tom w

I should add for those who don't know to check the GP's from the wire harness to ground. That way you'll verify the wire's integrity also.

I am definitely getting ratcheting wrenches for the next go-round!

I found my '79 240D getting harder to start, sometimes going thru 4-5 glow plug cycles before trying to start it. When I pulled out the plugs for replacement, I found the #2 had a short to ground in it... not a complete dead short there was voltage on all the glow plugs. (the engine would start on 3 cylinders,, pick up the 4th cyl after it warmed up a bit) Is this an unusual thing to have a gradually worsening ground? This is my first experience with MB diesels, an old dog trying to learn new tricks. olweasel
"Old age and treachery will overcome youth and strength"

Common
 

This is a common issue.

I think for some members removing the Glow Plugs is there 1st introduction to working on their Mercedes. And, it seems they are doing so without reading any manual.

So they do not want to remove the Hard Lines simply because they don't want to create another problem themselves.
Also from what I have read some folks do not want to deal with bleeding the air from between the IP and the Injectors.

For myself I have managed to drop 2 and lose one of the 8mm nuts even with the Injector Hard Lines removed. So I never plan to change GPs without removing the Hard Lines.

Recycled
 

for new members.

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Pelican sells a gp socket with an integrated swivel...