HOW TO: Remove a CDI injector with "black death"

[BlackC55]

Hello all.

I thought it was about time someone did a write up on how to remove a stuck injector, re-cut the head face and re-seal.

The car I am doing this on is an ML270CDI. Most of the rules apply to all CDI injectors. Make sure the engine is HOT. It will help.

Firstly remove the engine covers and determine which injector(s) are leaking. You can normally hear them but if you are unsure use some water or solvent on the rocker cover when the engine is running. You should see the leak easily.

With the engine off remove the injector electrical plug and high pressure pipe.

Clean all of the carbon from around the base of the injector and vacuum it all up. I use an old screwdriver and a large pick for this. Remove as much as you can and take your time doing it. Leaving a tiny loose lump of the carbon can cause it to enter the bore hole or bolt hole. I don't use any chemicals, coca cola etc. There is no need for it.

Undo the injector bolt. They can snap so be gentle.

Dig out the retaining clamp and vacuum any loose carbon. Clean the clamp of any deposits. When digging out the clamp, be careful as to not damage the rocker cover as its only soft aluminium.

Some injectors will be loose enough to remove now. Most wont be. If it is stuck then you need to use a special tool to remove it. Klann make a very good one or you can make your own. I have done both.

To use a slide hammer type tool you need to remove the injector top.

 

[BlackC55]

I use an adjustable spanner as it seems to fit the nut much better. Undo it fully and take it off. Be VERY CAREFUL not to loose the small spring and spacer that fits in the top.



This picture shows the top removed and the spring and spacer in the centre. The spacer goes in first. It is very small. Keep it dirt free.

 

[BlackC55]

This picture shows the injector in the head still.

I use a slide hammer with an old injector nut welded to the bottom of it.

 

[BlackC55]

Attach the slide hammer to the stuck injector. Make sure the nut is tight otherwise it will pull the threads to bits.



Then hammer the injector out!

 

[BlackC55]

Remove the injector from the slide hammer tool. Be gentle.

 

[BaldGuy]

very very clever dude...

 

[BlackC55]

Put the injector back together and clean it up. Get it spotless including the lowest face.

Pay attention to the condition of the face. If there are any signs of wear the replace the injector otherwise it WILL leak again.

 

[BlackC55]

The pic above shows the MB special grease that is used on the shaft of the injector for re-installation. The grease part number is A000 989 42 51 10 Always use gloves applying it.

 

[BlackC55]

The next step is to vacuum down the injector hole and all around the general area.

If you are lucky the copper washer came out with the injector but quite often its stuck at the bottom. Use a small long screwdriver and a hook to fish it out.

Then the injector shaft in the head needs to be cleaned. There is a Mercedes tool kit for this that is excellent. The part number is 611 589 00 68 00

In the kit there is brass blocker to be inserted in the hole at the bottom of the injector hole to stop any debris entering the cylinder. I strongly advise you use it when cleaning the shaft.

 

[BlackC55]

When the injector hole is clean you then need to re-cut the face of it. Remove the brass insert before you do.

 

[BlackC55]

As you can see in this pic (the seal is still down there) it can be quite a mess.

To re-cut the face I use a Sykes-Pickavant kit. Part number 0175000. Don't cut too much, just enough to make it a perfectly flat surface.

 

[BlackC55]

The next thing to do is to clean up the bolt hole thread. I use a special tap (available from ebay) with a dab of grease of the end of it.

Use your fingers first to wind it in and out. Be very very careful not to go too far or snap it in the head. If you snap it the cylinder head will have to be removed. If you go too far you will penetrate the water jacket.

Take your time and be patient. Get the thread clean as possible and remove all of the carbon that can clog it. If the threads are worn due to poor worksmanship before use a helicoil to repair it.

 

[BlackC55]

ALWAYS use a new bolt and copper seal. They are pennies from MB. Don't use any other type.

You need to make sure the injector retaining bolts goes deep enough to clamp enough. This is vital.

 

[BlackC55]

Now its time to put it all back together.

New washer on the end of the injector.





Insert the injector in the hole, fit the clamp and bolt, and then torque the bolt up.

The torque settings are for this engine (most CDI's) is 7nm and TWO angles of 90degrees. The 7nm crushes the washer. The first 90 tensions the bolt, the second puts a slight bend in the bolt so its slightly springy.

 

[BlackC55]

Fit back the electrical connector and HP pipe.

Turn the engine over a few times. It may take a while to start. This is quite normal.

Sometimes the force used to remove the injector can damage it. If that is the case replace it.

I know there are a few different methods to do this. Its whatever works for you. With the right tools it should only take an hour to do per injector.

You must make sure you vacuum at every stage to avoid the carbon entering the cylinder or bolt hole. One tiny bit of carbon can bend a con-rod.

I hope this helps out members.

Olly

 

[Koolvin]

now a item in HOW TO section.

 

[Gollom]

I am never going to do this myself. But I am in awe of someone who takes the time and trouble to write-up, In addition this same person could potentially see a loss of revenue by not charging to do it himself!

Bravo Olly - maybe everybody could take note and let this forum go back to what it was (and still can be sometimes). A place for knowledge, comradeship and fun!!!

 

[jaymanek]

Good how to Olly.

Just to add we have had a few where no slide hammer in the world will remove the injector, in this case the special klann removal tool is best but it does render the injector useless and you will need a new one.

 

[Lxb3]

Olly - many thanks, as ever, for posting an informative writeup.
Speaking as a non-diesel-owner (nothing against them, but one's never fallen in my lap, so to speak)... why are they such a sod on these engines, and what the HELL is all that carbon mess?!

 

[joecash]

I now know why I leave things like this to the professionals!!