I had compression air coming in a reman injector ... took me months to figure it out. I suspect that is pretty rare and in my case the car would not even run. However, that is where the froth would show up, in the return line on the back of the IP, not on any of the other lines. ckamila, if you recently replaced the injectors or if there's any chance you may have damaged a nozzle while doing other work, it might be worth considering. I think it was a pretty bizarre thing, though. Are your lines to and from the secondary filter clear enough to be really sure there aren't bubbles? I replaced them with new clear ones before feeling confident there were no bubbles in them ... before that they were browned and I had some doubts that maybe I wasn't seeing a froth in there.

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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)

Everything appears tight enough from the tank to the lift pump. Connection at the lift pump are more challenging and will look at tomorrow. All banjo fittings are tight too.

Looks like i have a little less air/froth in fuel return line but need some natural light to see better. Problem is far from resolved.

JB Weld center muffler repair looks to be holding so far at low temps.

thanks,

chris

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

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 may have overlooked it, but what's the problem other than seeing bubbles?
I was chasing mine dying out on me forever. Replaced all the lines, clear in the engine bay and had/have bubbles everywhere. Could never find the source of the air getting in. After all was said and done, a sticking lift pump was what was causing my issues. I still have bubbles, but I am so excited the dag-on car runs now, I don't care about the bubbles!

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'85 300TD- current toy
'04.5 Cummins- Daily Driver
'70 Chevelle- under construction
'63 Split Window- under construction

Yes, if where the Nozzle Pintle seat in the Nozzle is buggerd up combustion gas will get inside of the Injector. When you take the Injector apart you will see Carbon inside.

It will also happen if the Injector Spring breaks but that will give a noticiable miss.

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84 300D, 82 Volvo 244Gl Diesel

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

Did this air in the line cause any problems? I have had a perpetual rocking of the engine at idle that seems to come and go(none when cold). I also have these bubbles but at a much higher rpm. My car has loads of power and I have the ALDA valve bypassed with very little smoke at full throttle. I just wonder if in my case my pump has a problem internally. The shake has improved over the 3 years I have driven it but in neutral it still shakes with a audible miss at the tailpipe. In gear it will almost smooth idle, but it comes and goes. The biggest improvement came with 2 gallons of atf added to the fuel. I have done every thing except compression checked the engine.

Yep, I had air bubbles in my clear line going to the IP in a vw, Everything was tight, good filter, good fittings... but had a restriction coming out of the fuel tank due to rust (in the tank). The the diesel fuel pump is so strong (it circulates way more fuel than is actually injected) that if there is a restriction in the suction side of the fuel line system it sucked air in through perfect hose clamps. I think that's why bubbles are so common.

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1985 300TD 1981 Scirocco 1.6D conv 1986 Golf 1.6D 2003 Golf TDI

I was sucking air somewhere on my engine. I have the 124 version with an OM603 but the concept is the same on your 123 with OM617.

I replaced the 3 clear lines, that have banjo bolts, between the lift pump, the filter, and the IP.

I have clear return lines (Viton tubing) and before I replaced the 3 supply and main IP return lines, I had bubbles in the injector return lines at idle and when I revved up the engine in park (obviously I could not look at this while the car was going down the road...).

It caused difficult starting, it ran like crap once it was started, and idled rough until it had run for about 30-45 seconds.

After replacing the hoses, no more bubbles in any of the lines at all now. The above symptoms all went away.

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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

The reason the lift pump circulates more fuel than is needed to burn is so that the excess fuel cools the injector nozzles and the IP. Also you never want to starve the IP of fuel.

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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

Last week i did run a closed system - connected the IP supply and return lines to a bottle of fuel and had the same issue. Idle and starting are fine just lack of power from the foamy air/fuel mix.

I have since rebuilt a fuel pump and will likely try replacing soon.

I did have a cracked line from IP rerun line which i replaced. Since it's under pressure, i don't believe air would enter there.?

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

BodhiBenz1987 - Cracking the lines did result in bubbles/froth coming out.

Will see if the rebuilt lift pump changes the issue.

Thanks,

Chris

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

The thread is a bit old, but it seems that you raised the issue of air coming out of the IP return line, which is a problem I (and others) are experiencing. What did you do to confirm that compressed air came from the injector?

I have a thread diagnosing this same issue if you wish to contribute. Thank you!

OM617 injector return fuel flow and rough idle

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Theseus

Instragram: doss_project
1984 300SD - 930 Blue, OM 617
Murfreesboro, TN

Theseus owned a ship in Greek mythology, and when a part of the ship needed replacing, it was replaced. Eventually, everything was replaced. Is it the same ship? (I own the car of Theseus. )