I know the OM603's have very prominent top end noises thats completely normal.

I recently made some adjustment to the injection pump and a new noise started in the top end. It is a knocking type noise that you can hear echoing through the intake. The noise comes and goes, it is louder after a trip down the highway and then after some idling and driving around town the noise goes away.

If someone could point me in the right direction on stuff to look for to cure this knocking noise that would be very helpful.

With 200k miles, are the injectors due for a rebuild?

Thanks in advance!

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1986 300 SDL - HX30, Stock Pump, #314 Nozzles - Daily Driver/ Project

What kind of "adjustments" did you make to the IP? If the injectors are original then it's probably time for new nozzles. A metallic knocking noise high up in the engine is usually injector knock or "nailing" from dribbling or poor spray pattern.

__________________
Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

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

went from 1.5 turns out on the full load screw to a total of 2 turns out. same adjustment on the idle stop screw. I also turned in the allen head screw on the idle return spring in about 1/8 turn so it would return to idle at the regular speed.

It was running fine before and after I made the adjustments. Even with the knocking noise there is no affect on performance, just extra noise.

Maybe I should try a diesel purge to see if that helps at all.

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1986 300 SDL - HX30, Stock Pump, #314 Nozzles - Daily Driver/ Project

Was the knocking noise present before making the adjustments?

__________________
Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

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

It was not. I have a couple video clips, one with the knocks and one without. They’re giving me trouble when I try to attach them though

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1986 300 SDL - HX30, Stock Pump, #314 Nozzles - Daily Driver/ Project

You can't attach a video clip to this forum. Use a web host like Youtube and post the link back here.

Knocking after fiddling with the IP would suggest a fuel-related issue of some sort. Are you rolling coal on hard acceleration? Maybe you got the fuel adjustment out of whack somehow? Have you done anything else to the fuel system like filters or rubber hoses? Air will definitely cause nailing.

__________________
Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

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

It can smoke a decent amount if you want to leaving a stop sign. With normal driving it’s not much more than a light haze. Maybe I’ll adjust it back in a little bit and see if the knocking goes away a bit.

The only lines of changed fuel wise were the return lines that were leaking. Could air in that side of things cause them to nail?

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1986 300 SDL - HX30, Stock Pump, #314 Nozzles - Daily Driver/ Project

It can smoke a decent amount if you want to leaving a stop sign. With normal driving it’s not much more than a light haze. Maybe I’ll adjust it back in a little bit and see if the knocking goes away a bit.

The only lines of changed fuel wise were the return lines that were leaking. Could air in that side of things cause them to nail?

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1986 300 SDL - HX30, Stock Pump, #314 Nozzles - Daily Driver/ Project

If the old return lines were leaking, air was already in there (if fuel can get out, air can get in) so if you have air after a change, it should make no difference. Air in the fuel usually only affects the delivery side.

Turn the pump back to where it was and see if the noise goes away. If it does, you know it was related to your adjustment. If it doesn't, it was probably coincidental and now it's probably time for a set of injector nozzles.

What is it you're trying to accomplish by turning up the fuel in the pump? Smoke means unburnt (wasted) fuel, not more power.

__________________
Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

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

I agree with putting it back the way it was.

Way back when I was a Kid my mechanically inclined Neighbor told me that when you are trying to fix or adjust something only do one at a time and then test to see if it made a difference.

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84 300D, 82 Volvo 244Gl Diesel

I'm not really shooting for more smoke by turning the pump up. I'm mainly trying to get some more power out of it. With the pump where it is now, the power is great and the smoke is very controllable.

It is common to adjust both adjustments I made simultaneously as the idle stop screw needs to match the rack travel screw.

Is there a way ( or need) to bleed the return lines? I may just put new return lines on again when i rebuild the injectors.

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1986 300 SDL - HX30, Stock Pump, #314 Nozzles - Daily Driver/ Project

The return lines are self-bleeding when the engine runs. Since they're not on the delivery side of things, they're typically not bled.

Be aware that the M pump you have is slightly different than the MW pumps used on the 617's. You can tweak the fuel a bit without touching the idle adjustment. Typically it is only adjusted when there is an issue with idle quality. The EDS tends to keep the idle adjusted and will override the internal idle adjustments. Typically you adjust the idle controls with the EDS solenoid unplugged and aim for ~500-550RPM in park. Hunting idle or failing to idle after a rev indicates the need to adjust the idle stop.

__________________
Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

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

Okay that is good to know about the idle adjustment. Thank you for the help!

__________________
1986 300 SDL - HX30, Stock Pump, #314 Nozzles - Daily Driver/ Project

We understand you were not shooting for more smoke but more smoke due to your adjustments it indicates you are using/wasting more fuel then can be burned.

The people on the superturbodiesel forum fool with their fuel injection pumps more then people do on this forum. They could have more info on your issue.

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84 300D, 82 Volvo 244Gl Diesel

Found out what the noise was....

About a month ago I had my injectors rebuilt with new nozzles and the rattling went away, runs a lot smoother now as well.

Would definitely reccomend having injectors rebuild if you have a higher mileage motor.

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1986 300 SDL - HX30, Stock Pump, #314 Nozzles - Daily Driver/ Project