I just pulled into my parking spot and the engine began knocking like a gasser and "missing." I wager it is an an injector issue. It's too dark right now for me to do anything, so I will have a look tomorrow and crack the fuel lines.

Will a good couple rounds of purge possibly cure the issue? Yes, no, maybe?

Will it hurt anything to drive it 12-20 miles a day until parts arrive? If yes, how about quick commutes less than 5 miles?

I welcome offers on known good used injectors. I'll purchase the 5 I just sold with a markup too!

I had to look up that you have an 84 300D. You should post what vehicle you have when you ask questions.

A common cause of sudden nailing is you got some bad Fuel and you are getting air sucked in on the suction side of the Fuel Supply/Lift Pump.

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84 300D, 82 Volvo 244Gl Diesel

I would check it further and try to pinpoint which injector is nailing. I had a faulty spray pattern after cleaning the injectors and totally dismantleing them which I was told I should not have done anyway blew out bottom of my prechamber cylinder 4 on my 617 motor is still sitting on my garage floor. It happened 500 miles from home while traveling about 80 mph. wish I would have checked it out sooner had to replace engine.

Since the sound appears to go along with a rough idle (missing), it is likely not due to your mechanical vacuum pump. If it were, I wouldn't drive anymore since my son drove 100 mi home w/ a tapping sound and I found the arm on the vacuum pump worn half thru (bearing on roller failed). Any more and it would have slid into the timing chain with bad results. It took a while to determine the sound was likely from the vac pump.

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1984 & 1985 CA 300D's
1964 & 65 Mopar's - Valiant, Dart, Newport
1996 & 2002 Chrysler minivans

Crack each fuel line to see if you can find out which injector is making noise.
Run some diesel purge and give it some Italian tune ups.

Don't rush out and buy injectors just yet, it could just be bad fuel.
Check your plastic fuel filter to see if it's infected...

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1998 Ford Escort ZX2 5 speed - 279,000 miles My Daily

1992 Mercedes 300D 2.5 202,000 - Pure junk
2000 Mercedes E320 Black - 136,000 miles - Needs repair

Don't forget to grease the screw and threads on the spring compressor.

I lost my low mileage chevy diesel engine due to a 'sledge hammer' type knock that developed less than 10 miles from dealer after injector pump replacement under warranty.

Had the truck towed back to dealer. They charged me for replacing injector but did not replace the glow plug for that cylinder. I didn't know they should have done so. Less than 100 miles later that cylinder went out because the glow plug tip had burnt off during the excessive knocking. Guess it bounced around in the prechamber until it passed through & took the top of the piston out and rod busted the block.