Fuel pump delivery valve seals.

[Parrot of Doom]

This thread details how to change the o-rings and crush washers on the diesel delivery valves, for the OM606 engine (commonly found in the E300TD). The same procedures can be used on a range of other Mercedes diesel engines, although not modern CDi engines.

 

[Parrot of Doom]

Most fuel leaks on the OM606 engine happen around the fuel pump, specifically the plastic fuel lines between the pump and the two fuel filters. These, while a bit inaccessible, are generally a quick and easy job to replace.

Tools:

Mercedes splined tool part no - 617 589 01 09 00
6 x copper seal (7f)
6 x o-ring (7h)
Sockets, torque wrench, torx bits, extensions, etc

The fuel leak we fixed today was on the other side of the pump - the injector side. This is where fuel is pumped out at high pressure, down hard metal lines, into the injectors, and thus into the engine. The leak was at the 6 valves on top of the pump (1 valve for each cylinder). There are 6 o-rings (the source of the leaks) and 6 crush washers to replace. To access these valves, the intake manifold must be removed, as well as the washer bottle and all 6 injector lines. Its probably not a job for an amateur DIYer like myself, which is why I was very glad to have my mate with me, who is much more experienced in these matters than I am. Its a good idea to have 2 people on this job anyway, since a spare pair of hands is invaluable for catching hold of loose springs, holding clamps, etc.

1) Remove washer bottle

1 bolt holds my bottle in place. Remove that, and pull the bottle to the front of the car - it will unclip itself from a small bracket. Remove any connectors on the top, and put it out of harm's way (I left it resting on the +ve battery terminal).

2) Remove intake manifold.

Full instructions can be found in the EGR cleaning thread. Essentially theres 1 bolt accessed from above, this unclamps the small pipe that enters the EGR valve to the back of the engine. Another bolt below (allen IIRC) holds 2 aircon pipes to a clamp, said clamp also is bolted onto the chassis. There are 12 torx bolts on the top of the manifold screwed into the head.

Once these are all removed, the intake manifold should come completely clear.

3) Remove injector lines

The 6 injector lines must be removed from the pump, and the injectors. This is easy enough, just a normal spanner can be used. Unscrew each line, its easier to start with line 6 (rearmost cylinder) and work down to line 1. As you unscrew each line, take care not to mix them up.

A simple way to avoid mixing them up is just to leave each line hanging in the relevant injector well. Another tip is to take a photograph of the arrangement, or you could tie a small label on each one.

Once you've removed all 6 lines, you should be looking at this:

You can see we've grouped 4 injector lines together on the right of the pump, the other 2 are at the left of the pump out of shot. If you look closely, you can see diesel welling up at the top of each delivery valve (its blue).

4) Remove splined collars

Each delivery valve is held in place by a splined collar. This collar is designed to stop the delivery valve from moving once it has been torqued to the fuel pump - if this collar wasn't there, then once you put the injector line on the valve and began tightening it, the delivery valve would start rotating in sympathy.

There are 6 collars, held in position by 3 bolts. Remove all 3 bolts. The collars will be stuck to the head with age and grime (and diesel). Get a flat bladed screwdriver and bend it 90' in a vice - this gives you a nice lever to get them up. Work them back and forth, they'll start moving. Then just lift them off.

From the picture above you can see the installation order - collars 1, 3, 5 are first on, followed by 2, 4, 6. They overlap.

 

[Parrot of Doom]

Once all 6 collars are off, you should be looking at this:

The collars will be filthy - chuck them in a bucket of degreaser for now.

5) Removing the delivery valves

With the special Mercedes tool, unscrew delivery valve 6 - carefully.

As the valve is removed, there will be a tall slim spring resting inside the pump - take care this doesn't fall out into the engine bay.

The o-ring should be above the thread on the valve you just removed - if it isn't there, it will be stuck in the fuel pump here:

(you can just make it out, above the thread)

 

[Parrot of Doom]

In the image above you can see the crush washer (part 7f). This needs to be removed. Insert the end of a flat screwdriver under the lip of the washer, and gently slide it out.

Now the crush washer rests on a metal collar, the collar holds a very small cylinder of metal. This cylinder, from what we could gather, when the engine is running pushes against the spring and allows a small amount of fuel up the lines, through the injectors, and into the engine. I have been repeatedly warned not to disturb this but to my surprise the collar and little cylinder were quite happy to slide around inside the pump - they can't really not move, because the pump isn't horizontal anyway, its tilted to one side.

I think what may have happened is that someone has torqued the delivery valve back down, not taking care to ensure the collar is correctly centred in that little well, and the little cylinder hasn't been able to fully move - which would probably lead to damaged seals inside the pump, and a damaged delivery valve.

Anyway, we removed it just to have a look:

There appear to be no keyways or anything, the pdf file (I will link it at the end) just says "observe the installed position". There is a groove along one edge, we just compared it to the collar on valve 5 and aligned it in the same direction. The little cylinder is flat to the top edge (with a small serial number stamped in), the bottom edge looks like a phillips screwdriver blade - probably so the diesel can counteract the rotational forces applied on the top edge when it pushes against the spring.

Obviously you don't have to remove this collar or the little cylinder, so don't unless you're curious. If you do remove it, make sure it goes back in the correct orientation, and clean.

Put the new crush washer in place, and slide your new o-ring over the thread of the delivery valve. Your fingers will be covered in diesel and oil anyway, but if they're not just make sure the o-ring is wet with oil/diesel, to ensure a better seal while torquing down.

Carefully put the spring back in the pump, and ensure the collar (7g) is centered in the chamber.

Screw the delivery valve back down with your fingers, waggle it back and forth as you do so the collar, crush washer, and spring are all forced to align themselves correctly inside the delivery valve (the inside of the valve is slightly fluted to aid this).

 

[Parrot of Doom]

Repeat the above steps for the 5 remaining valves.

6) Putting things back together

Once the valves have all been screwed in by hand, get the torque wrench out and torque each valve up to 26 ft/lb (35 nm). Slide the collars back over the spines (taking care to observe the order they were removed), and screw the collars back down with the 3 screws. You should be looking at this:

Screw each injector line back onto the valves, starting with line 1 working through to line 6. No torque figure for these, just tighten them up, then an eighth/quarter turn more, and that should be that. Then screw each line back onto it's injector, observing the same degree of tightness:

Take care that the fuel lines are correctly aligned - there are plastic clips to guide them. Watch that no plastic fuel lines get in the way.

Reinstall the intake manifold - this is a pig of a job and you'll need 4 hands to do it. Theres no way to describe it, just put it back together (refer to the EGR thread if you like). Use gasket paste to ensure a better seal between the manifold and the head (we reused the existing gasket, its metal and still a good seal)

You can of course clean the oily crud from the intake manifold if you like, and the EGR as well. You'll need a bottle brush and some degreaser for that.

7) Crank like crazy

This is where your battery gets tested. There will be loads of air in the system now, and you're going to have to crank for a good 2-3 minutes (crank no more than 10 seconds a time, with 20 seconds inbetween).

My battery gave up the ghost here, so I nipped down the local autofactors and bought a new one. Well its had a good 5 years anyway, and was getting a bit tired. Plus I got it at trade price, so it only cost me £50

Eventually the engine should fire back to life, it will stumble a bit but once the air has been pushed out the system it will be fine. Leave it running for 5 minutes to restore some charge to the battery.


I did have a heart in mouth moment on the way home, a massive THUNK from under the bonnet - fortunately it was the pipe from the turbo popping out of the EGR valve under the manifold. Either not inserted fully, or a clamp has broken, either way at least it wasn't the fuel pump exploding

Hope this all helps!

 

[Parrot of Doom]

Schematic of delivery valve here:

http://homepage.ntlworld.com/tom.jeffs4/car stuff/merc tech/diesel delivery reseal-1-1.pdf

Bigger pictures here:

http://www.flickr.com/photos/soundman/sets/72157603792018546/

I forgot - heres a picture of the reason why they were all leaking:

And here's a very square (should be round) cross sectioned o-ring:

 

[Parrot of Doom]

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http://forums.mercedesclub.org.uk/showthread.php?t=35288