[1908 300D non-T] So I got the test & rebuild kit from ************** and knocked this out yesterday. Was my first time doing anything like this, but not bad at all. Got it back together and there is no doubt it runs better at speed and has more get-up-and-go. But I swear the engine has more 'knock'/'rattle' than it did before.

I have new engine mounts I intend to put in shortly... is it possible with better functioning injectors that bad mount-related noises are louder? It seems to me the noise is coming from within the engine (valve cover), but I find it very difficult to confidently identify the area-source of noises when this is running. It is tempting to tell myself this is it and move on...but I worry there might be something going on (after my work) that I should not ignore.

Thanks,
Brice

Brice,

If the engine now produces a sharper more prounced and slightly louder clack vs a flatter muffled sound that is good. It is how they sound when correct, a quiet 615, 616 or 617 isn't "dialed in." Or worse yet, has low compression, sounds crazy but better is a little sharper and clackier on these. I had a '78 240D that was really quiet...needed a rebuild due to low compression, after the rebuild she definitely announced herself!

Have the valves been adjusted? It is critical on these, don't overlook them.

Good luck!!!

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"Rudeness is a weak man's imitation of strength" - Eric Hoffer

Thanks @Sugar Bear. That puts my mind at ease.
And yeah, I adjusted valves a few weeks ago when I did a compression test (~320 across the board, cold). I think I'm good!

You may or may not have lapped the parts properly. That being said I have experienced need to break in nozzles with both Rebuilt and New injectors. In some cases the injector did not settle within a reasonable time and i replaced it. Try driving your car hard for a while and se if it improves. A couple of high speed runs should break them in. You can identify remaining nailing injectors and replace as you see necessary. Use a mechanics stethoscope.

I do not bother with rebuilds anymore. I buy new bosch from a vendor with lifetime replacement guarantee and replace stubborn injectors if i encounter them.

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Rindfleischetikettierungsüberwachungsaufgabenübertragungsgesetz

Thanks for the insight @R.Diesel. I lapped them until I could see no rings/marks, but who knows. Replacing injectors sounds like a solid move with lifetime replacement guarantees (any recommended vendors for these?).

Also, any links to a protocol for using a mechanics stethoscope to determine which injector is not working properly? That sounds like a handy diagnosis.

What was used to test the Injectors?

Basio nozzles are noisier then the Monarks or the Bosch Nozzles.

I only skimmed over the other posts so I may mention things already mentioned.

There is valve timing which is related to timing chain stretch and there is also Fuel Injection Pump timing.
Also some people have said that the new Nozzles need to sort of run in a bit and then there is a little decrease in the noise. I always wondered if the decrease in noise was simply that people go used to the noise as the new normal.

If you Engine has adjustable valves that also.

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84 300D, 82 Volvo 244Gl Diesel

The new nozzles are Bosch, as were those that I removed. I tested them using the bench-top injector pressure tester from **************. It worked pretty much like the videos and was straightforward. New spray pattern much better than old.

Took it for a 10 mile spin, much at 70mph this morning. She is much rougher upon cold start than ever before (I have to give a fair bit of gas to keep from stalling) and WAY more smoke.
Runs great at speed and idles well once run, no more smoke.

I'm not convinced all is right with the system given the issues at cold start. I'll put another 30+ miles on her today at speed and see how things go.

Any insight on diagnostic measures I might take would be much appreciated (identifying 'nailing' injectors, timing on chain, timing on IP).

For the cold start issue check your glow plugs. If you change any glow plugs use only Bosch or Beru glow plugs and use a glow plug reamer or some other means to clean the carbon out of the glow plug holes.

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84 300D, 82 Volvo 244Gl Diesel

Sounds like the rebuild wasn't done properly. When you checked your pop pressure, were the injectors all balanced? Did you shim them to the correct pop pressure? Did you pay attention to pattern, post-"pee", and leak down rate? All of it is important. Post-"pee" and internal leak down are your biggest enemies, they'll result in rough running, smoke, and hard starting.

Your non-turbo engine takes 115bar injection pressure, 1666PSI +/-50PSI max, preferably +/-25PSI for smooth running.

If you're using Bosch nozzles made in India, be aware that they suck out loud. Poor spray pattern, poor longevity, and high internal leak down.

If in doubt about your abilities or what you're looking for, consider sending your injectors (and the original nozzles) to forum member Greazzer (his website is: https://dieselfuelinjector.guru) and make sure they are done right rather than risking burning a hole in a prechamber.

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Current stable:
1995 E320 157K (Nancy)
1983 500SL 125K (SLoL)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Gone and wanting to forget:
1985 524TD 167K (TotalDumpster™) [Definitely NOT a Benz]

Thanks @Diseasel300. These details are super helpful.
The injectors all 'popped' right around the same point, +/- 50 PSI, I did not have to add to or remove shims from those that had been in the injectors.

Leakdown is when I get it up to near pop pressure and hold to see if I get leakage out of the nozzle, yes? I had one that leaked a small stream upon first build, pulled it apart and lapped again, and it was gone.

What is Post-"pee"? That is a new one to me. Some googling suggests it is a small steady stream after pop? I saw none of that.

Any non-Bosch nozzle recommendations? Someone also recommended full-new injectors from vendors with lifetime guarantees.

I will surely reach out to Greazzer shortly if I can't get this sorted. Don't want to let my desire to learn and do-myself do harm to the car.

Was the pop pressure correct? 115bar = 1666.667PSI. 1650PSI on your gauge for easiest measurement. Post-pop pressure is important too. If you pop at 1650PSI but the injector nozzle resets at 1400PSI, that's 250PSI you have to rebuild before it pops again and the injection quantity/timing may be badly skewed as a result. A good nozzle should be less than 100PSI between pop and reset, meaning the pintle moves freely and seals well.
Leakdown is pump the injector up until it is almost about to pop, then stop and watch the pressure gauge. Pressure will drop, but it should be very slow. If you get more than a 500PSI drop in <30 seconds, you have an internal leak down problem and need to do more lapping and/or injector torquing. Lapping involves the face of the upper injector half, both sides of the center "disc", and the upper face of the injector nozzle (pull the pintle out before you lap it, and clean very well). I personally like to use a scrap piece of 1/4" glass for my lapping surface and finish with 4000 grit paper and never have a leak.

After the nozzle pops, sometimes they'll have a little stream, a drip, or a dribble. After the nozzle shuts, there should be nothing at all, not even a drip. If the pintle is moving properly, you should get a rapid chattering of the injector as you make a medium speed sweep with the pop tester handle.
Bosio and Monark are the big ones that people go for. Monark are out of production and very expensive. Bosio have been difficult to obtain lately. Firad seems to have picked up where Bosio left off. I have a set in my 350SD and they seem every bit as good as the Monarks I had in my 300SDL.
Learning to DIY is a powerful tool. If this is an engine you care about, get a 2nd set of junk injectors from a junkyard somewhere and teach yourself to rebuild/shim/test/clean them. If you keep the car, you'll be doing it from time to time anyway. For the injectors you're running now, you might consider having a pro set them up for you. When you get them back, throw them on your pop tester and see what you're looking for in a good nozzle. A bad nozzle can damage the prechamber and can wreck your engine if left unchecked! It doesn't take long with a squirting or dribbling injector to do irreparable harm.

__________________
Current stable:
1995 E320 157K (Nancy)
1983 500SL 125K (SLoL)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Gone and wanting to forget:
1985 524TD 167K (TotalDumpster™) [Definitely NOT a Benz]

Not sure if this site still works or not. I agree with everything but think you should use something better to do the lapping.

How to Rebuild Injectors
vincewaldon.com - HOW-TO: Rebuild Diesel IDI Injectors

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84 300D, 82 Volvo 244Gl Diesel

I would hesitate to open things again unless you don't have confidence in your work.

My engine (617.910) sounded like a rock crusher at idle when I put rebuilt monark nozzles in. I was pretty worried, but I had confidence in my work so I didn't second guess it enough to open things again. It took 500 miles to quiet down, but it sure did! No issues in last 10K miles since.

-Henry

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1976 Mercedes-Benz 300D, Colorado Beige / Mahogany
www.hmclever.com

I would just send your injectors to injectorguru pay the 100 bucks and be done with it...

This seems like the most logical issue. It's your first time rebuilding injectors and there is just something small that you did wrong. It happens to me all the time.

So it's either take them all back out and double check everything or just pay $100 and have brand new injectors.

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Rebuilt many of these injectors,never had a problem that made it to the car.
Yes new injectors or rebuilt may be a little louder,but if sounds like a rock crusher,than the
nozzles are hanging,may or may not come out of it.
Some causes:poor fuel,over tightening,pintle to tight in barrel,not clean enough,metal
from bending steel lines,nozzle under distortion from unseen carbon in injector lower body
half. Best of luck.