That's good news!

Regarding the idle still a little rough, that could be caused by injectors out of balance. They need to be set with opening pressures that fall into a five-bar range for a smooth idle. It could also be cause the accumulated carbon build-up on a pre-chamber, which will just take awhile to burn out.

Or in my case, it could just be a tired old engine that's had a hard life! It isn't objectionable anymore, so I'm not worried about it. Car needs a road trip badly, but still have some driveline issues to solve before it can. I have a hunch that a nice road trip will cure a lot of what ails it.

That's awesome Diseasel300! Thanks for the follow up. I've got the springs, seals and o-rings in hand myself now. Something about the copper seals and o-rings - they are the same as used in the pump on the OM616 in the '74. I already had some laying around and didn't even know it! :)

Still gonna run the purge through out of curiosity and because it's not been done yet on this engine, and then get into the DVs.

All good, mine was like that too, really puzzled as to where the cloudiness came from - only thing I could think of was small amounts of engine oil (pump internals are lubed by engine)must be making its way in there somehow, either that or the fuel is murky.

Not sure tbh.

Gmog220d:

Your video sounds EXACTLY like my car, but yours may be a bit louder. Same symptoms: light knocking at idle, gets louder as revs increase, but (almost) disappearing after 1,400 rpms. Runs perfectly smoothly at higher rpms.

I never got the nailing to go away - even after replacing the DV crush washers. However, I did NOT replace the DV springs. I'm really curious to know what your outcome will be. I hope yours gets fixed. I'll regret not having replaced the springs, but at least I'll know a fix is at hand!

Good Luck, and I'm keeping my fingers crossed for you!

P.S:
BTW, I've got a 1995 606 with 412,000+ miles on it. I had the head off about 100,000 miles ago due to an external seep. Other than that, no issues at all. Still runs like a champ. These 606's are very long-lived beasts!

Nice of you to show up, RTH! Thanks for the good vibes. It'll be 2 - 3 weeks until I get around to working on the E300's DVs. Got work coming up and a fresh radiator leak bumped the DVs down the list a bit. I'll report back on my results when I get the job done.

I did get the rebuild kit for the IP, but it's not what I expected. Bosch DGK127. It's for a 4 cylinder pump, so it's short 2 sets of copper seals and o-rings for the DVs (I've got them, from the 240D's stash). It's got some of the parts needed for rebuilding the lift pump, but not all. Side and bottom plate gaskets are not correct. Not a total loss, but I wouldn't do that again. I was told Bosch apparently no longer supplies a kit for the 6 cylinder IPs, and expects you to make up the difference with your own stock of parts. Oh well. Lesson learned.

I've got two 5 packs of the springs, though! :)

I'm learning to like the OM606. Everything seems like it was designed with service in mind, and I appreciate that. It's a pretty crazy assortment of o-rings that goes into it, though! :cool3:

Mine was pretty nasty. Actually had little "chunkies" floating around in there. Fuel coming from the tank is clean and clear and the DV holders were spotless, so I can only assume it was something (corrosion?) coming off the threaded areas as the DV holders came out. Needless to say, I didn't want to leave it in there, so it got cleaned out.

My original springs were a good 2mm shorter than the new ones I installed. They didn't seem any heavier, so I can only assume they were compressed/tired. My car was nailing LOUDLY (almost embarrassingly so) when it warmed up, and replacing the DV seals, O-rings, and springs has gotten rid of it. Drove the car to work this morning and to do my afternoon errands and it's remarkable how quiet and refined it's become. I'm happy! Your mileage may vary, as they say...

I've been wondering about their purpose myself. I stumbled onto this video:

https://www.youtube.com/watch?v=OeRm_95ETog

The presenter talks about the purpose of delivery valves starting at 2:15. Looks like they are pretty much a check valve, one that maintains a base pressure in the injector lines so they are primed and ready for injection with less effort and/or time.

Nothing specific about specs and testing in that video, though.

So does a weak or broken DV compression spring produce a lean condition, or rich? Or does it cause timing to be off a little?

Just some fortuitous timing, as I don't check in here nearly as often as before.

I'd agree, with the sole exception of those *$#@^ glow plugs. As for the fuel system O-rings, believe it or not, Amazon had all the correct size nitrile o-rings available. You get a bunch of them for only a few dollars per size. Well worth the effort, even if you don't run biodiesel. (I normally don't, but I did put in some B-20 while in Portland a few weeks back, just for the heck of it.)

Speaking of bio fuels, I'm up in the SF Bay Area again for a few weeks - and I filled up on the Propel fuels HPR. Amazing stuff with a super high cetane rating. My engine loves the stuff, and it even reduced the intensity of the knock. The fact that it reduces that knock leads me down a wild chain of hypotheticals. Take this theory with a grain or two of salt, but it sounds plausible.

If the DV is not sealing (i.e., it is leaking internally) the residual pressure in the hard line is not held high enough, therefore it takes more volume of fuel during the injection stroke to reach the injector opening pressure. Since it takes more fuel volume during the pump stroke to reach opening pressure, injection is delayed in relation to crankshaft timing.

Of course, this also means that the overall balance of fuel delivery (for that cylinder) will also be reduced, resulting in uneven running. When the pump timing advances with rpm's or fuel volume is increased due to more fuel demand, it seems to mitigate the problem to some degree.

The higher cetane level of the HPR may be causing the spray to ignite just slightly earlier, equivalent to a teeny bit more advance. This may account for the reduced knock sound and smoother running at low rpm's. Just a wild thought...

If you're problem is solved with the new DV springs, I'd tend to think it goes towards validating my hypothesis. Can hardly wait to know what happens!

My own theory on why the DV's can cause nailing/knock (and no I don't have any scientific data to back up my claims!):

The DV's act as a check valve. As the pumping element rises, it pushes out a metered displacement of fuel. When the pressure is high enough to unseat the DV, the fuel passes through, into the hard line, and forces the injector pintle off its seat to inject fuel.

When the pumping element reaches the top of its stroke, the pressure drops, the spring pushes the DV closed, the injector pintle seats, and the standing pressure in the hard line keeps a maintained seal. The pumping element now retracts, refills with fuel, and is ready for another pumping cycle.

Now assume you have weak springs, a DV that isn't seating properly (worn, gunk in it, improperly torqued), or a crush/sealing washer that isn't maintaining a proper seal.

When the pumping cycle is over, fuel leaks down and bleeds off pressure in the hard line. The next time the DV is unseated to pump fuel, part of the pumping element's stroke is used to refill the hard line before enough standing pressure is attained to unseat the injector pintle.

The result: late injection timing AND a lean charge. Since the prechamber is supposed to be a rich mixture in relation to the piston cavity, a lean and late charge here means part of the combustion is happening in the prechamber instead of in the piston combustion chamber. Hello knock...

When the RPM is increased, not only does the volume of fuel pumped increase, but the increase in pumping rate helps to counteract the leakdown that's happening at the DV's. Thus, you get above a certain RPM and suddenly everything appears happy on the surface since a larger volume of fuel is being injected.

I could be way off base here, but based on my understanding of how an IDI diesel works, it certainly seems plausible to me.

Some anecdotal evidence: Before the DV's were overhauled in my IP, the first start of the day could be fairly rough. One cylinder would hard miss for 10 seconds or so, and it wasn't uncommon to have the entire engine shaking and dancing around for a bit before suddenly becoming smooth and quiet. Post DV service, the engine starts on the first compression hit and is smooth as glass from the very first start in the morning. I was starting to suspect I had a glow plug or two out, despite them all being new of June of 2016, but it turned out to be DV issues, not glow plugs.

It's a logical and well stated theory. The only thing I'd nit pick is the order of events:

1 - DV opens;
2 - Pintle opens;
3 - Pintle closes;
4 - DV closes; and
5 - Back to 1.

Small detail. The end result, late and lean, seems reasonable.

I'll go along with that. Like I said, no data to back up my theory, but it seems plausible.

Yeah, I'm curious too! Need to order up a copy of that DV socket . . .

It all seems logical - weak springs throwing off fuel volume and timing. I'll most likely order up the few seals I lack and springs for the DVs in the '74, too.

I would change this a smidge as the nozzle cannot open with out a hydraulic lock between both ends (if that makes sense)

1 - DV opens with cam lobe at bottom drawing in fuel;
2.- Cam lobe rotates upwards closing DV with requisite amount of go juice
3 - Cam continues, DV seals, lock created
4 - Pintle forced open as cam continues;
5 - Pintle closes;
6 - DV opens; and
7 - Back to 1.

From memory the amount of fuel is governed by the cam in some fashion, although not certain how.

Here's the mini cam.

https://www.youtube.com/watch?v=pJ9uqm2nsgE

You are confusing the "fuel rack" with the "delivery valve". The delivery valve is nothing more than a fancy check valve in the output stream of the pumping element.

The hydraulic lock comes when the pumping element crosses past the spill slot in the fuel rack. At that point, it is a positive displacement pump and the pressure forces the DV off its seat and moves fuel into the hard line.

The fuel rack is a groove that adjusts when the pumping element stops spilling and starts pumping. The sooner the piston crosses the spill slot, the larger the amount of fuel pumped.