Glad you figured it out! Weird. Are you going to dissect the injector and let us know?

But before I go through removing the VC again to get the injector out I'm gonna order the correct tool for it. Again, the OM606 is not very convenient for the simple stuff but I'm sure it's a great engine. I'll keep ya posted!

Injector is not closing properly and when you loosen the hardline a little cylinder compression gas is coming back through the injector? This appearing like air in the fuel at that point that it actually is. Perhaps some dirt in it or the spring broke? Does not matter really though as should be pretty easy and cheap fix. My guess is dirt.

I'll take it apart and see what may be the problem.

Sounds promising.at least you've eliminated injector pump/delivery valve seals.

As Barry mentioned, you have probably picked up some dirt and run it through the injector.

I hope you cleaned the top of the injector pump before you did your delivery valve seals?!

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1995 E300 Diesel

Thankfully my pump was very clean prior to the job BUT I used brake parts cleaner and I small tooth brush to clean the top after I removed the locking collars. It was very clean. Now, to find an injector socket.

Try ordering from dealer at MB Northlake (Charlotte), they seem to have decent prices.

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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 buy all of my dealer items from them. Wayne, the parts guy, is good to deal with.

Instead of buying the socket from the dealer at $130 I went to Harbor Frieght and bought a socket set for oxygen sensors and diesel injection systems for $40. I'll give all the unneeded sockets out as Christmas presents this year.

Anyway, I removed the injector, disassembled it, cleaned it, reassembled it, then reinstalled it. Problem gone!

Good news, enjoy it.

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1995 E300 Diesel

Sooooooooo quiet. Sooooooooo smooth. Another injector had some light nailing but it's nonexistent now on the purge. The smoke is lighter but there's still some smoke. The engine does have 364k on it so some smoking may be acceptable...even with a new head (?). I'm not getting my hopes up at the moment because I can't run it on Diesel Purge forever. We'll see what happens when I go back to diesel.

With 364k you might be due for some new nozzles-depends on many factors such as quality of diesel its been run on etc. I'd just run it for a while until you get to know it, if that makes any sense. Everything you've done so far ticks off necessary maintenance items for this engine.

Have you checked/replaced your screen filter in the tank? It requires a large 46mm socket to r and r. Mine was terribly clogged and previous water in the tank had pitted the filter.
I also ordered and replaced the rubber 'tail' (300mm long) which screws into the bottom of the tank and joins onto the hard line. It was perished and weeping diesel which is another place for air to get in. I also replaced the return whilst I was there which was standard fuel hose 5'16 from memory. It's another project for another day as you'll get diesel all over your hands no matter how careful you are.

Is your smoke at idle and does it smell like burning oil or diesel?

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1995 E300 Diesel

There may be some carbon deposits from the faulty injector that will cause smoking until they are burned out.

The engine is running smoothly. No misfires or scary loud knocking. Injector #5 is nailing at idle but I'll get to that soon enough. I went on a short test drive and I'm satisfied. Tomorrow I will drain the cooling system and thoroughly flush the oil residue from where the coolant to oil heat exchanger leaked internally. After that it goes to the detail shop so I can steam clean the engine and the underbelly before the encapsulation panels go back on.

As I read it.......Possibly a broken spring in the injector body or pintle needle seizing....but unlikely.

2 seconds of squirt is a long time. There had to be air in the line to the injector to cause that, being as fuel is not compressible and would, like the others, only squirt a little drop of fuel as pressure was released.

...but being as the knock followed the injector, I would dismantle the injector.

However...on reflection...if the injector needle was not closing there could have been residual cylinder pressure bleeding back through the injector.

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