Just to get them out? No more than 1/2 hour tops. If you are rebuilding the same injectors then it will take longer. If you have new injectors ready to go you should be in and out in under an hour.

It is easiest with the injector lines removed. If you want to put a plastic bag over the IP, fine, I guess I never felt the need to when removing the lines. Very little fuel comes out of the lines. IMO, not enough to worry about anything other than having a paper towel nearby.

Like was mentioned if you use a breaker bar on the injectors they come loose real quick. The heat shields take more time to get out than the injectors themselves. I used a pair of needlenose pliers to break them loose and then a magnetic tool picker-upper to get them out. Some come out with out breaking loose and just the magnetic tool.

This would be a good time to change out the injector return lines as well.

I guess the rule is to make sure the injector area is as clean as possible BEFORE you remove the injectors, not after.

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2009 ML320 Bluetec
1985 300CD
1981 300TD

Past Mercedes
1979 300TD
1982 300TD
2000 E320 4Matic Wagon
1998 E430
1984 300SD
1980 300SD