On the way home from work, after about 45 miles of interstate, I pulled on to highway to my home and I noticed a loud knocking. I'm not a diesel guy, so it just sounded like rod knock to me.

Got home and upon further inspection it sounded more like an injector nailing. The nailing is somewhat erratic and there is a miss that's varies in intensity as well. The nailing goes away when I crack the line to the 3rd injector. The miss intensified somewhat.

I have some observations:

1) It seems weird to suddenly develop such loud nailing (I generally work on gas and HEUI injected powerstrokes)

2) Why does the nailing intensity change?

3) There's a ton of air, almost no fuel, in the fuel return line between 2 and 3. I replaced that line today while I had it apart (after the issue) because the was diesel in the injector well. None of the other look that way. What could cause this?

Did my injector just bite the dust?

For your viewing pleasure, some one-handed shake came footage:

https://photos.app.goo.gl/Rgbjaiz43Kcoo5hn7

https://photos.app.goo.gl/mF1CatjBoN31S1SH9

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1997 E300 Diesel - 222K miles

did somewhere let air in the IP?

Zero bubbles in all the feed lines and relatively new delivery valve seals.

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1997 E300 Diesel - 222K miles

what type are these injectors? Are they like mine rebuildable or?

Have you got these bench tested?

swich them around and see if the sound follows the injector. You need a stethoscope for it to be somewhat easily identifiable. otherwise try a long screwdriver.

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Rindfleischetikettierungsüberwachungsaufgabenübertragungsgesetz

That's a ton of air in those return lines, pop the fuel cap listening for a whoosh of air - could be tank vent is blocked.

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David


1996 Mercedes S124 E300TD - 129k - rolling restoration project -

1998 Mercedes W210 300TD - 118k (assimilated into above vehicle)

Just a follow up, moved the suspected injector around and the hard nailing followed it. Got remaned Bosch India injector for cheap from Advance Auto Parts and slapped it in yesterday. The new injector is a little noisy, but the engine runs smooth now. The new injector has quieted a little in the 100 or so miles I put on it today.

I'll eventually get the injectors rebuilt and balanced, but it's a little pricey driving the superduty everyday with a daily commute of over 100 miles.

One observation on the new injector: the fuel return ports were wider than my old injector, wide enough that they didn't fit my injector socket. No big deal, I just hit the socket with a die grinder opened it up a bit. But that would have sucked for someone with fewer resources.

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1997 E300 Diesel - 222K miles