So after checking my 1979 Mercedes 300SD, there seems to be a small fuel leak coming from the pump. I have checked and it seems to be coming from the delivery valve o-rings.

I get alot of conflicting information regarding where to get new ones, part numbers and how to replace them. I have been told I can't without re-calibrating the pump. Some people have told me it will be fine as long as I re-torque it properly and don't mess up the shims.

The car still runs. I really would like just to replace the o-rings and be on my way but not if it causes bigger problems. Here are some videos of the leak:

https://www.dropbox.com/s/c1hbkbrc4jaikj7/VID_20180129_163153.mp4?dl=0
https://www.dropbox.com/s/jbf3qwkc8rst3ne/VID_20180128_170130.mp4?dl=0

Thanks
Alan

Video did not work for me . Antone else have problems?

Videos work fine for me, I'm using chrome.
Have you ruled out that it's not leaking where the injector line screws onto the DV? It doesn't look like that, but it's worth cleaning everything really well so you can pinpoint the exact leak.

Cursory search found a video and a post saying it isn't a big deal:
OM617 Delivery Valve Seals
https://www.youtube.com/watch?v=RA9iC7yOd74

Just don't touch the two outer nuts that hold the adjustment plate down, and you shouldn't throw your pump out of whack.

__________________
1984 300TD -- summer daily driver
Many others that aren't Mercedes...

I can't view the video. If like the IP on my OM617 turbo engines, there are no O-rings. The seal is a flat copper washer. They don't usually start leaking, but perhaps the delivery valve unscrewed slightly (not torqued correctly?). No problem taking it apart, but get good photos because a little tricky to orient all the innards correctly, especially which way to turn the thickest disk (can barely make out in the FSM photo). I think the delivery valve is just a check-valve and doesn't affect the piston volume. As stated, don't touch to 2 large nuts on the locking plate. If you did, that would affect the calibration.

__________________
1984 & 1985 CA 300D's
1964 & 65 Mopar's - Valiant, Dart, Newport
1996 & 2002 Chrysler minivans

Diesel is so thin it wicks and spreads super fast so you have to be creative in spotting the source.

1. spray the entire area clean with Brake clean

2. start engine watch and see if you can isolate which injector(s) are leaking.

3. Once you have identified the leaking injector(s), it may still be difficult to determine exactly where it's leaking from since diesel is clear and thin and flows quickly. Spray dray the injectors again with Brake clean. Cut strips of a white cotton tee shirts and wrap 2 turns each (tie a knot so it does not unravel) around the following spots:

-top of injector line nut
-bottom of injector line nut
-base of injector

Start engine and watch. The piece of cotton tee that wets first is the source of the leak.

__________________
85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

https://www.youtube.com/watch?v=uNn_Ko5dsDM&t=23m05s

There is an o-ring on the valve. I think it that o-ring is the one leaking.


I think I will have to in order to replace the o-ring there (see video 8 lines above)

I will definitely do that to check. Maybe not tonight since it is snowing.

So I checked yesterday before the superbowl and it is 100% leaking from the base. It is definitely leaking from that O-ring between the pump body and delivery valve.



Now the question is, how do I replace it? In theory, if I the shims are kept the same, the orientation is marked on the base screws (the rotation of the delivery valve), the pump delivery shouldn't change right?

Thanks for all the help so far guys!

No, I think that O-ring is for keeping engine (and IP) lubrication oil inside the pump and dirt outside the pump. Don't go that far, only remove the delivery valve and replace the copper washer inside. Clean clean clean, and make sure you use a torque wrench set to proper torque to install.

__________________
Respectfully,
/s/
M. Dillon
'87 124.193 (300TD) "White Whale", ~392k miles, 3.5l IP fitted
'95 124.131 (E300) "Sapphire", 380k miles
'73 Balboa 20 "Sanctification"
Charleston SC

Hmm from my testing it didn't look like it was coming from the upper part of the delivery valve but I will check again.

Watch that video again, the part of the injection pump in Diesel Giant's gloved hand is covered with engine oil below that o-ring.

__________________
Respectfully,
/s/
M. Dillon
'87 124.193 (300TD) "White Whale", ~392k miles, 3.5l IP fitted
'95 124.131 (E300) "Sapphire", 380k miles
'73 Balboa 20 "Sanctification"
Charleston SC

yeah that does make sense but then now the question is where the heck is this dang thing leaking from? I will have to do another video and use paper towels this time.

Leak is either from the DV or the hard fuel line right above it. Sometimes you have to just take it apart and closely examine the seals and joints to figure it out. Have you tried just putting a wrench on it and tightening things up just a bit? Would be nice to find out that it simply has gotten a bit loose with time.

__________________
Respectfully,
/s/
M. Dillon
'87 124.193 (300TD) "White Whale", ~392k miles, 3.5l IP fitted
'95 124.131 (E300) "Sapphire", 380k miles
'73 Balboa 20 "Sanctification"
Charleston SC

I will definitely try that next. Would you recommend any special wrenches or will regular/flared wrenched work fine?

That is all that you can do. If that does not work you either have it calibrated or find anothe used Fuel Injection Pump that does not leak.

You might be the 4th person on this forum to have changed the lower O-rings.

__________________
84 300D, 82 Volvo 244Gl Diesel

I didn't end up going outside today because it is so cold but honestly, that does make sense. Even if the ring ripped, it would let oil through, not diesel. I need to do a better test to figure out where this leak is from.

Thanks for all the help guys seriously.