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1980 300TD
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Discussion Starter · #1 ·
Hi all!
New to the group and though I have found many helpful posts, I still have numerous new ones! Let's start with just one simple one. I am having several problems with the engine, and to me, the best place to start is by removing the fuel injectors to check the compression. I put a socket on the first one and tried to turn it. I felt if I pulled any harder I would break it off. Am I missing some sort of lock or something? Or do they just come out that hard? The engine is quite clean, so I do not expect rust.
 

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77 450 SL
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613 Posts
They are in there pretty well. I used a breaker bar to get mine out. Don't forget new heat shields when you reinstall. Also, while the injectors are out, that is the perfect time to do a visual on your glow plugs to verify they are working.
 

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'77 6.9, 74 240D, 96 Ram 5.9L Cummins
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2,654 Posts
I haven't removed injectors personally since I don't have a proper torque wrench to retighten them to the correct torque, but it seems that you could spray the threading with some penetrating oil or something to loosen them up if they're dry or have crud down the threading.
 

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2013 MINI Copper S Clubman, '84 300CD-weekend car
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10,152 Posts
I haven't removed injectors personally since I don't have a proper torque wrench to retighten them to the correct torque, but it seems that you could spray the threading with some penetrating oil or something to loosen them up if they're dry or have crud down the threading.
Agreed, I've taken out a few. Used a 1 1/16 inch 1/2 inch drive socket. They've been in there a long time, but doubt you'll do any damage... to the car!
 

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1980 300TD
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10 Posts
Discussion Starter · #6 ·
OK, sounds like it's just bloody knuckle time! I just ordered a set of glow plugs and a set of injector heat shields (3 out of 5 plugs were bad) guess that's probably my hard starting problem. So I am going to wait until the parts come to do a compression test so I don't have to remove the plugs twice. Thanks all for the info.
 

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1984 Mercedes-Benz 300SD Turbo; 1985 300CD Turbo
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163 Posts
I just did this job about 2 months ago. I suggest you do a valve adjustment before checking the compression to make sure you get a correct reading on each cylinder. In fact, I would say that it is critical in order to get an appropriate reading. I have heard that readings could go from 200 lbs. of compresion before an adjustment and then increased to over 300lbs. after a V-adjustment.

Secondly, I sprayed some WD40 on mine before removing them, which seemed to work. Mine too were on there pretty tight. Just like Zedd mentioned, 55lbs. of torque is the appropriate amount of torque. Furthermore, Harbor Freight is selling a 1/2 drive torque wrench with 10-110lbs. of torque, right now for $9.99. H.F. are not the best tools on the planet; however, I have NEVER had any issues with any of the tools that I have purchased from them.

Secondly, DO NOT forget the heat shields. MB manual recommends that they must be replaced each time an injector is removed. They come out with ease with a flat head screwdriver and a magnet.

It's an easy job. Good luck friend.

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'84 300D/ dakota benz trk. Sold... miss it. "88 260E '91 190E 2.6 '89 Volvo 240DL "85 300D
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1,252 Posts
what tools are you guys usiing to test compression? i have a compression tester rated up to 1200 psi. but it stops at a quick connect and i dont know what to purchase to attach from there to the head. is there a better kit out there you all are using?
 

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2013 MINI Copper S Clubman, '84 300CD-weekend car
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10,152 Posts
^^Mine, a U.S. General (made in china) came with a number of fittings that quick connection.
 

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1980 300TD
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10 Posts
Discussion Starter · #10 ·
Good idea about the valve adjustment, I probably would have forgotten about that until after putting all the injectors back in! I do have several torque wrenches, thanks for the info. Novice
 
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