Had some hard starting issues other morning at 9 degrees glow plug light on dash was not coming on checked plugs found 1st (2) bad back 3 tested good glad they were as they are even harder to get at then front 2 was wondering if it makes it easier if you disconnect injector lines.Did get it started by shooting some either in air cleaner I know that is not good but just seems the WD 40 does not cut it even with the either I had to crank couple of seconds with the assist of a battery charger.Was also thinking of drilling a small hole in U tube right before intake and putting a small screw or plug in there so I have quicker access for starting assist.You would think that glow plugs would last longer as I just did replace all 5 with Bosch about 2 yrs. ago.

It is certainly way better if you fix the problem than shoot even WD-40 into the intake.

I find it easier to get at the Glow Plugs with the Fuel Injection Hard Lines removed.

But, if someone who has never had the Fuel Injection Lines off of their Engine reads this they need to know how to bleed the Air out of them after they put them back on; just in case they have some hard Starting.

If you remove any Glow Plugs reaming or otherwise cleaning the Carbon out of the holes helps them to last longer.
Along with this the Condition of your Injector Nozzles, Pop/Opening pressure and your Fuel Injection Pump timing have an effect on how long your Glow Plugs will last.

More info:
Repair Links
DIY Links by Parts Category - PeachParts Mercedes ShopForum

PeachPartsWiki: Do It Yourself Articles - Mercedes Vehicles

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84 300D, 82 Volvo 244Gl Diesel

Ether is a no-no, you run a small risk of cracking a pre-chamber and destroying your engine. Much better to follow Diesel911's advice and fix the problem.

Assuming your car has a OM617 engine, removing the fuel lines to change the glow plugs is a good idea, just keep it clean-clean-clean. Put painter's tape over the open ends of the lines and over the injection pump connections and the injector connections, as any dirt that gets in can clog an injector and cause you more problems.

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Respectfully,
/s/
M. Dillon
'87 124.193 (300TD) "White Whale", ~392k miles, 3.5l IP fitted
'95 124.131 (E300) "Sapphire", 380k miles
'73 Balboa 20 "Sanctification"
Charleston SC

I've never found it necessary to remove the injector lines to replace glow plugs. Others have.

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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 simply stick the removed Fuel Injection Hard Lines into a clean Plastic Bag and lay the Bag inside of my Garage someplace where dripping Fuel will not damage anything.

As Kerry said some people do not remove the Fuel Injection Hard Lines when they remove the Glow Plugs.

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84 300D, 82 Volvo 244Gl Diesel

I usually remove the injector lines. I've done it both ways, and it's easier for me with then off. I've also never had to reprime the injector lines. But if you do it's as simple as cracking the injector end of the hard lines while cranking the engine to purge out the air.

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I have to join the boat.. My 300SD had a hartd time starting today and it was 40*. I am going to need to do the glowplugs in my SD but I wanted to know.. What about the reaming situation? Do I direly need to do this? Could I just do with replacing the Glowplugs, GP relay, I already have a new battery.

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No one can make you Ream out your Glow Plug holes but your Glow Plugs will have a better chance of lasting a long time.

In the DIY section there is some alternative ways to clean out the Holes.
There also is some Reamers in the Tool Rental Section.

The shortest one in the pic is the one that would fit your year of SD.

The longer ones are used on the Engines with an Aluminum Head.

Attached Thumbnails

 

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84 300D, 82 Volvo 244Gl Diesel

Carbon reaming requirement depends on your engine; if your engine is healthy and you drive it like you stole it, there probably is almost zero carbon and reaming is not required. If you drive in town a lot, you may have a lot of carbon. If you get heavy smoke under full throttle, you probably need to ream.

A cheap but effective reamer can be made from a used glow plug; hammer the heating element flat and install/remove in each hole.

__________________
Respectfully,
/s/
M. Dillon
'87 124.193 (300TD) "White Whale", ~392k miles, 3.5l IP fitted
'95 124.131 (E300) "Sapphire", 380k miles
'73 Balboa 20 "Sanctification"
Charleston SC

Opinion:
While the above is true most of us bought used Cars from owners who never had the Injectors rebuilt, never had Valves adjusted or never had the Fuel Injection Pump Timing re-set.

I am not sure flattening the Heating Element of a no good Glow Plug is best thing on an Engine with an Aluminum Cylinder Head. It could scratch up the bore.

Of the alternative methods I have read for cleaning out the Carbon from the Glow Plug Holes in the DIY section; simply buying a 7mm Drill Bit provides the correct sizsw and twisting it only by hand should keep it from damaging anything (the factory made reamer is 7mm in diameter).

For myself having the correct Tool increases my chance of actually getting out and doing the job; because I know the job is going to get done right with the least chance of problems.

Below is about 2 years of Carbon from a 617.952 that spends most of the time driving in the City.
I live in Southern CA and still Ream my Glow Plug Holes when the Plugs come out; because I have the tool available.

Attached Thumbnails

 

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84 300D, 82 Volvo 244Gl Diesel