Hi, all-

My 91 300D 2.5 Turbo IP just started leaking diesel at the top, from around the output to the rear cylinder, just at the base of the strange thing that connects from the IP to the injection line. What are those things anyway, and why do they have the splined area with the metal tabs to hold them from rotating?

I assume that there is some sort of O ring or something in there, maybe that got degraded by many years of biodiesel use. How do I remove the splined thing to replace the O ring, and is the adjustment critical? If I count the turns to unscrew the thing and screw it back in the same amount will that work, or is there some other adjustment procedure?

Thanks for any help..


Max Behensky

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1981 Datsun King Cab Diesel pickup
1982 240D 4 speed manual
1987 300TD wagon
1991 300D 2.5 turbo

Hello, Welcome.
check this link out:http://www.peachparts.com/Wikka/OM602InjPumpFuelLeak

It's time consuming but cheap.

The soft hoses do wear out and need to be replaced they return fuel that isn't used back to the fuel system.

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92 300D 2.5L OM602 OBK #59

Your thinking is right. Special splined socket and just a certain torque. See the wiki:
http://www.peachparts.com/Wikka/OM606DeliveryValveSeals

Thanks for the great info and links. I'll try this tomorrow (I think I'm going to just do the one that leaks and leave the others alone for now)...


Max Behensky

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1981 Datsun King Cab Diesel pickup
1982 240D 4 speed manual
1987 300TD wagon
1991 300D 2.5 turbo

If your in there you're better off doing all. Do you have the special socket?

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92 300D 2.5L OM602 OBK #59

I didn't want to pay $40 (and wait) for the splined socket to remove the diesel delivery valves, so I took two of the lock rings from an extra injection pump I have and brazed them onto the end of an old 13/16 spark plug socket. I used two rings for more torque, but I'm not sure that was necessary. To make sure the rings were lined up properly, I slipped them over the splined valve together, and clamped the tails with vise grip pliers. I then brazed them onto the socket, ground off the tabs, and I had a tool that worked pretty well.

For my 2.5 turbo engine, I was able to just unscrew the injector lines and move them to the side, after removing the locking rings. I then could unscrew the valves without much trouble. I tilted the valves to the side and stuck my finger over the end before removing them to prevent the spring from falling out.

I had purchased both the O rings and crush washers, but I didn't want to start pulling stuff out of the IP to remove the crush washers. I just replaced the O rings and put everything back together. I didn't have a torque wrench that would fit, so I re-torqued the valves by hand to what felt like the torque I had to use to remove them.

The process was easy enough that I replaced all 5 O rings, not just the one that was leaking. The engine ran rough for a little while after I started it, but after it smoothed out the leak was gone. The whole thing took maybe half an hour (not including the time to make the tool).

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1981 Datsun King Cab Diesel pickup
1982 240D 4 speed manual
1987 300TD wagon
1991 300D 2.5 turbo

That's ingenious! Check the condition of the injector line holders (plastic). From what I understand if you're missing them it will shorten the life of the lines from the vibrations and possible rubbing. The roughness usually works it way out in a few hundred miles.

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92 300D 2.5L OM602 OBK #59