Well, yes, i did just have my injectors cleaned an balanced. IF i pop test them for spray pattern and pressure setting, will that be enough to tell?

Also i don't have any idle issues or an unbalanced engine as more throttle is added. Seems if i suffered from the same issue you did there would be other signs.

Return line is new so nice and clear. The other 2 (from the lift pump to primary filter and from filter to IP) are brown and yes harder to tell for sure no bubbles are passing.

I'll see if i can post some video of the bubble surge tomorrow.

thanks,

chris

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1985 300D, 250k
1980 300SD, 180K

On my faulty injector, when the fuel-line nut on top of the injector was cracked, bubbles/froth would come out interminably (which for a long time I had assumed were coming from the IP). You could try just cracking the nut on each injector, one at a time, and looking for bubbles (including as you apply some throttle). If none of them bubble I don't think that's the problem. If you're seeing air coming out of one line, you could try taking that one out and pop testing it ... if spray pattern and pressure are OK, I don't think you have a nozzle problem. I wish I had taken my faulty one to get pop tested (or dissected) but I needed to send it back to get the warranty honored ... would have been interesting to see what it did.
I do also think if you had this problem, you would be having more issues with the way the engine was running. Mine would only run on three cylinders, and if I tightened down that line, it would airlock and stop running altogether.
I would probably pursue the simpler solutions first (leak on the supply side of the lift pump), but I thought it was worth mentioning that it is technically possible to have air get into the pump on the other side.

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1987 300D, arctic white/palomino--314,000 miles
1978 240D 4-speed, Euro Delivery, light ivory/bamboo--370,000 miles
2005 Jeep Liberty CRD Limited, light khaki/slate--140,000 miles
2018 Chevy Cruze diesel, 6-speed manual, satin steel metallic/kalahari--19,000 miles
1982 Peugeot 505 diesel, 4-speed manual, blue/blue, 130,000 miles
1995 S320, black/parchment--34,000 miles (Dad's car)

I think it would be easier to leave the Injectors on the Engine and replace the Fuel Return lines with ClearTubing and see if you are getting bubbles out of the Injectors.
For a temp look I suppose any cheap clear plastic tubing might work.

If you want to leave the clear Fuel Retun Lines on the Injectors some Members have used: 1/8" ID
Oregon (as in Chainsaw) Brand, it is a Tygon fuel hose.
Tygothane (Saint Gobain is the Manufacturer)
U.S. Plastics is the retailer.
That they bought at a Lawn Mower Supply Shop.

.

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84 300D, 82 Volvo 244Gl Diesel

Youtube video link IMG 0104 - YouTube showing air in return line. Best view around the 1 minute mark since video is rotated 90 degrees..

chris

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1985 300D, 250k
1980 300SD, 180K