OM606 Fuel Pump Rebuild - PeachParts Mercedes-Benz Forum

tankowner · #1 11-22-2010, 09:45 AM

Well, those fuel pumps are getting on in the years now, so if you have the urge to rebuild one, maybe this will help. For me, my problem was a fuel leak on my '95 300D (606.910) - I knew it was leaking from the delivery valve seals, but I figured that I would reseal (and ultimately replace the valves) in the fuel pump while I was in there. In the end, this project turned out to be a little more than I bargained for because I didn't really know what I was doing. But hindsight is 20/20 and, in retrospect, the job is not too bad - maybe this write-up will help someone else.

Some prior threads were started to get some help along the way. See http://www.peachparts.com/shopforum/showthread.php?t=285915
and
http://www.peachparts.com/shopforum/showthread.php?t=286198
if you are interested.

Much thanks to Diesel911 for help and advice during this job!!!!

Let's get started:

1. Remove the cross-over pipe (COP). There are some 10 mm bolts that hold the pipe to the bracket and another 10 mm bolt that holds the other end to the IM. There is also a vacuum line underneath that attaches to the resonance flap in the COP - remove the line from the actuator. [Note: I did this at the same time I did my delivery valve seals, so I had removed the cross-over pipe and intake manifold (IM). Even if you aren't messing with your delivery valves, I'd still go this route - you just have a much better view of what is going on - and easier access (I doubt I could have removed the old gasket with the IM in the way).]

2. If you have never taken the control mechanisms apart before - take a picture now before you do. You'll thank yourself later.

3. Remove the intake manifold. You'll need to undo the Bowden cable and a couple of connecting rods - one to the IP and one to the vacuum control flap near the ERG. Pop the sockets off the balls with a flat screwdriver being careful not to damage them. Unbolt the accelerator control bracket and move it out of the way. Prior to removing the IM, it's a good idea to clean around its mating surface - you can use a small brush and some compressed air to remove any crud. Remove the IM bolts. There are vacuum lines and electrical connections that are attached to some components on the underside of the IM (See Picture 1) - these are also for the various resonance flaps - undo the lines/connectors, noting how they reattach and labeling if necessary. Pull the IM from the engine bay and set aside. Note: Observe all proper torque specification when reassembling – torque specs for the IM bolts is 20 Nm - if you don’t have a torque wrench, get one now.

4. Time to take another picture - this time get a couple of the various vacuum connections (see my example, Picture 2). You may want to undo some of the vacuum lines for better access. If so, label them accordingly so you know how to reassemble. An ounce of prevention is worth a pound of diagnostics later to figure out why your transmission is shifting horribly – ask me how I know.

tankowner · #2 11-22-2010, 09:53 AM

5. The fuel pump is located on the side of the IP. There are two fuel lines running to and fro. The one furthest from the IP is letting fuel in from the primary filter and the one nearest the IP is sending fuel up to the secondary (spin on) filter prior to moving it on to the IP. If your IP and fuel pump are covered in crud, blast them with some brake cleaner before you start taking thing apart. Remove the fuel lines by pushing the white U-shaped clips in and pulling the lines out. I replaced all of my plastic fuel lines during this job and, by default, also changed out all of the associated o-rings (they come with the new lines). If you aren’t going to replace your fuel lines, you should at least renew the o-rings while you have them apart. If they aren’t leaking yet, they will no doubt start leaking once you have everything back together.

tankowner · #3 11-22-2010, 09:58 AM

6. Remove the two 10 mm nuts holding the fuel pump onto the IP. Note: Be prepare for the engine oil that is going to come out when you pull fuel pump off the IP – it’s not a lot, but enough to justify a catch pan.

Picture 1: Removing the fuel pump.

Picture 2: Here is the fuel pump removed.

Picture 3: And here is the IP minus the fuel pump; you can see the old gasket still in place.

tankowner · #4 11-22-2010, 10:11 AM

7. Okay. Now to get into the fuel pump. First you will want to remove the fitting with the piston rod running through it. Probably easiest if you hold the pump in a vice – don’t crush it, just wrap a rag around it and clamp down on it so it won’t move. The front fitting is 19 mm. Oh, and there is big spring inside, so be prepared as you unscrew the fitting. Then you can remove the top brass fitting, which I think is a 22 mm, but I used a 7/8” that worked just fine. Here is an exploded view of what it looks like disassembled at this point.

tankowner · #5 11-22-2010, 10:14 AM

8. Get some parts. Wait, so what exactly are we replacing? Well, you can buy an entire rebuild kit (check out this link from whunter: http://www.peachparts.com/shopforum/showthread.php?t=240104) through Fastlane/AllPartExpress which includes the following:

000 091 10 19 SPRING
000 091 13 10 VALVE (X2)
023 997 87 48 SEAL RING
023 997 86 48 SEAL RING
000 091 17 80 GASKET
021 997 88 48 SEAL

If after reading this you want to replace everything, then buy the kit through the forum – it’s well priced and you get it all at once. I started out by running to the dealer to grab the o-rings, then back later for something else, then back later for . . . . you get the picture. Note that when I ordered the o-ring with part # 021 997 88 48, the dealer told me it had been replaced with # 012 997 72 45 – that is what I bought and used.

Here is what it all looks like. Note that this is a diagram of only the parts in the kit and this does not show all the individual components of the pump. Also, only one valve is illustrated, the other one lives under the top fitting (that the fuel return line attaches to):

tankowner · #6 11-22-2010, 10:18 AM

9. Start by replacing the little o-ring (023 997 86 48) that seals the piston rod. Just push the rod out of the fitting and you’ll see it hiding in there. I used a dental pick to pull it out. Note the orientation of the rod, one end is a little tapered.

tankowner · #7 11-22-2010, 10:21 AM

10. Replace the o-ring (023 997 87 48), it is the larger green one in the picture below. In that picture you also see the inner valve housing and (on the very end) one of the valves. I suppose now is the time to discuss the valves.

tankowner · #8 11-22-2010, 10:25 AM

11. Okay, I don’t know what the life expectancy on these little valves is supposed to be, but I decided to replace them. The one in the previous picture is not hard to do. I simply inserted a small screw driver into the “top” of the housing and pushed it out.

Picture 1: Here is what it looks like inside the housing.

Pciture 2: Insert screw driver here, apply a little leveraging force, and . . .

Picture 3: Voilà!

Simply replace with a new valve. The new valve I put in did not want to stick in there, but I didn’t see the need to apply adhesive or anything else that might muck up the works since the valve is held in place and can’t move once everything is reassembled. If you’re concerned about it, I suppose you could do a very thin bead of RTV or JB Weld around the outside of the valve before reinstalling.

tankowner · #9 11-22-2010, 10:34 AM

12. Now on to the second valve in the upper brass fitting – this one is trickier.

Picture1: Here is that upper fitting removed from the pump body. Oh, and you’ll want to replace the o-ring here as well. It’s part # 021 997 88 48, but again, the dealer told me it had been replaced with # 012 997 72 45 – that is what I bought and used.

So the valve is inside the brass fitting. Thinking that I could just push it out, like the previous one, I inserted a punch through the top of the fitting and then proceeded to hammer it out. Uh, bad idea. The fitting is actually pressed around the valve, so that a small lip holds it in.

Picture 2: You can see the new valve sitting on top of the fitting to illustrate that the valve itself has a larger diameter than the opening in the fitting it is pressed into (obviously not apparent to me at first).

Picture 3: Clearly, I mucked it up trying to get it out, as you can see in the pic.

Picture 4: And this is what the old valve looked like when it came out (in comparison to a new valve) . . .

tankowner · #10 11-22-2010, 10:36 AM

13. At that point I wasn’t sure exactly what the best fix was, but Diesel911 suggested grinding down the damaged section of the lip so that the new valve could be inserted and then sealing with JB Weld – ultimately that is what I did and it worked out well.

Picture 1: Here it is after some grinding:

Picture 2: And here is the new valve held in with some JB (dried overnight):

tankowner · #11 11-22-2010, 10:39 AM

14. Time to put it all back together:

tankowner · #12 11-22-2010, 10:41 AM

15. Don’t forget to remove the old gasket. Mine was really stuck on there. I had to use a razor blade to carefully scrape it off. Here it is all cleaned up and ready for a new gasket (#000 091 17 80).

tankowner · #13 11-22-2010, 10:42 AM

16. As they say, reassembly is the reverse:

tankowner · #14 11-22-2010, 10:47 AM

17. Getting those fuel lines back on the pump can be a pain once they have new o-ring on them.

Picture 1: You can place the blade of a flat screwdriver on the line fitting, like so . . . (yeah, that’s a dirty old line I tested it out on first)

Picture 2: . . and then gently, tap it down in ( I used a rubber mallet – gently).

tankowner · #15 11-22-2010, 10:48 AM

18. Take the rest of the day off to think about how happy you are that your fuel pump is ready to deliver thousands of more gallons of diesel to your beloved Mercedes. I’ve rolled about 500 miles on since doing this job – no problems. Have fun!

- Mark