I hesitate to post this because I'm running a modified injector pump but I remember the car doing this to a degree before the modifications.

Here's the setup:

• Engine "pings" while cruising at all speeds from 45 MPH and up to 75+ MPH.
• At a standstill, if I rev the engine to about 2100 RPM and then give it a further blip of the throttle, I get a burst of clatter from the engine. Maybe normal?
• If I'm cruising at highway speed, engine pinging away and I accelerate gently or start climbing a hill, the engine gets dead quiet.
• If I accelerate hard from a standstill, the engine performs perfectly with no extra noises.

Some theories and things I've done to fix this:

• At first I thought it was late injection noise so I advanced the timing but that made it worse (more cylinders pinging instead of just one)
• Secondly, I thought it was poor sealing of the delivery valve crush washers so I replaced them and re-torqued them. This solved an idle shake but not the pinging.
• Third, I replaced the delivery valves in the pinging cylinders and that didn't help as well.

So I thought I'd throw it out there and see if you all have any ideas. My next step will be to remove the IP and verify the accuracy of the element timings. Which, on a side note, would be much easier if I had a section of degree tape for the damper. Then I wouldn't have to pull the pump. Anyone know of a source?


Thanks for the help as always.

__________________
-Evan


Benz Fleet:
1968 UNIMOG 404.114
1998 E300
2008 E63


Non-Benz Fleet:
1992 Aerostar
1993 MR2
2000 F250

How's your low pressure side looking?

I had similar symptoms, it was an air incursion.
Until I changed all of these, I got clattering like that.
- Fuel lines and o-rings
- pre filter o-ring (on mine there was crud on the sealing surface so check that)
- the o-ring behind the shut off valve - that finally cured it

__________________
The OM 642/722.9 powered family
Still going strong
2014 ML350 Bluetec (wife's DD)
2013 E350 Bluetec (my DD)

both my kids cars went to junkyard in 2023
2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles)
2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles)

1998 E300DT sold to TimFreeh
1987 300TD sold to vstech

That's a good thought. My low pressure side has been fine for so long, maybe I'm missing something. I have replaced all of the o rings with viton several years ago and I haven't payed much attention to them since.

I'll go check that right now.

__________________
-Evan


Benz Fleet:
1968 UNIMOG 404.114
1998 E300
2008 E63


Non-Benz Fleet:
1992 Aerostar
1993 MR2
2000 F250

OK, so i got a flashlight and held it behind the fuel lines and saw some motion, especially when I revved the engine up a little. I think the problem has been that in the past, I have used a LED flashlight and that tends to hide the bubbles because of the strobe effect. This time, I used a standard light and they were easier to see.

The bubbles are starting at the fuel heater so I'm assuming they may be coming from the badly cracked rubber hose or possibly the o ring on the heater itself. Time to start replacing some parts!

We'll see how it works and go from there, thanks for the suggestion. Sometimes it pays to go back to basics.

__________________
-Evan


Benz Fleet:
1968 UNIMOG 404.114
1998 E300
2008 E63


Non-Benz Fleet:
1992 Aerostar
1993 MR2
2000 F250

I would be curious to see if premium diesel did anything.

__________________
1999 Mercedes E300TD daily driver sold at 238K miles 106K miles were mine, rust worm got it :-(
2006 Mercedes CDI new daily driver! 56,000 miles May 2016 now 85,625 Apr 2018 and Apr 2019 101,000 miles Apr 2020 109,875. March 2024 135,250

Economical source of "O" rings

McMaster-Carr

According to here 9464K44 works BUT I have measured and I feel that 9464K23 is a better fit.

I tried to order both but McMaster will not export them, evidently some hi-tech gov't secret restricted product.

I ended up going with all new lines with O rings.

__________________
1999 Mercedes E300TD daily driver sold at 238K miles 106K miles were mine, rust worm got it :-(
2006 Mercedes CDI new daily driver! 56,000 miles May 2016 now 85,625 Apr 2018 and Apr 2019 101,000 miles Apr 2020 109,875. March 2024 135,250

The o rings were replaced not too many years ago with a complete viton kit I bought from a member here. The only part I haven't replaced is the rubber line in the engine compartment. Looking at it today, it's in pretty rough shape.

__________________
-Evan


Benz Fleet:
1968 UNIMOG 404.114
1998 E300
2008 E63


Non-Benz Fleet:
1992 Aerostar
1993 MR2
2000 F250

Sorry to dredge up an old thread. I'm having the same issue you described in the original post (albeit on a 95 E300D). I thought perhaps it was too much timing so I retarted the timing by a half turn with no change. I had previously advanced it by a turn because I replaced the injectors at 260k miles and it seemed down in power. I digress, did you end up fixing it? Was it indeed air incursion?