Finished rebuilding the 4U,  It runs a little rough so I cracked each nut at the injector pump.  When I open #2 it runs smoother but air is coming out along with the diesel.  When I tighten it up it starts running rough again.  The other nuts when cracked all just put out diesel but no air.  Could  gasses be getting back into the injector?  I can swap injectors to see if things change but wanted to ask before doing anything.  All new injectors and Precomps.  Thanks for advice, Gary

Go ahead and rotate the nozzle to another cylinder.
If it still leaks combustion air it is either a bad nozzle or the nozzle isn't seating in the chamber.

Thank you OM. I will do that and report back.

Hi OM, I did some experimenting and here are my observations. #2 was the problem so I changed to a new nozzle, no luck. Changed to new adapter with new nozzle, no luck. I swapped precomps from 2-1 and problem followed to #1. I am wondering if I don't tighten the nozzle to the adapter, maybe 1/4-1/2 turn will it seat better? the precomp is a 1S1970 that has been modified to 1"x12 pitch. No bubbles in radiator. Any Ideas? Thanks, Gary

Here are links to two videos.

Appears there is a seating problem with #2 pre-com chamber.
Nozzles should only be screwed on finger tight.
Maximum torque for the nozzle assembly is 100 ft-lbs. Any tighter can distort the nozzle.
Check the pre-com nozzle seat, may have a burr or piece of foreign matter that is preventing sealing.
Looks like you may be needing a new chamber.

Because you're using D4 chambers modified to fit a D2, the bottom of the chamber needs to be chamfered... yours may have been done, but not quite enough.

Problem solved I think....
I think they were done correctly but I will keep that in mind.
I changed nozzles, Again. 3rd new nozzle worked. Tight to 100#. The others I just tightened as much as possible with 1/2" ratchet. It's working now on phase 3 of break in procedure (light load at 3/4 speed)
Thank You Very Much OM for your ideas. Gary

As tight as possible with a 1/2" ratchet???
Why not proper torque on them all?
Sounds pretty good in your video.
I'm pretty sure all the nozzles are sourced from the land of "almost right" no matter who you get them from. Seems common to have to sort through a batch to get them right.

Hi OM,
I did not read the service mans book on the nozzles at 100#. I will go back and check again.
When reading the book to confirm the 100# on nozzles, I noticed on page 100 it says precomps to 200#, then on page 143 it says 150#.
Your thoughts?
Thanks,
Gary