I'm not stating a theory. It's well established in science and there are plenty of papers out there backing up the claim. Just because YOU didn't notice any difference doesn't mean it wasn't there.

I am new to pop testing.

I've rebuilt, lapped and replaced Bosch nozzles with Monarch.

Now I'm adding on pop testing.

Of the 14 nozzles I've worked on Ive only seen 2 that had any shims at all.

When its time to balence them, if a shim is called for, and MB thinnest shim in parts fische is 1 mm thick, that theoreticlly increases pop pressure by a lot. I've read each .05mm in shim thickness increases pop pressure 100 psi. (from Robs meredes corner, he seem meticulous) so a 1mm shim is way too much. How does one add a shim that brings a smaller change in pop pressure.

How does one deal with this connundrum??

Thanks in advance.

See your other thread. http://www.peachparts.com/shopforum/diesel-discussion/395968-pop-test-apparent-connundrum.html

Shims are made in significantly thinner sizes than 1mm. If you're adjusting pressures, buy a kit and shim as necessary. I'd suspect someone has been in those nozzles before if none of them have shims. Are you sure they're not just stuck in the top of the upper injector holder?

That is a great suggestion. I will check, verify

thx

You nailed Mr D
now it makes sense

thx again

https://www.mcmaster.com/98055A095
I think these work, but i haven't bought any myself
they have .2, .3, .5. and 1mm also


Sanding (polishing) the sealing surfaces of the injector body will make a tiny increase pop pressure as the spring technically gets compressed more when you put the injector back together.

It can be a real pia getting the correct pressure you want if you're not good at it or some unlucky factor comes into play.

Thx

Yes I believe about the PIA part

I am thinking about replaceing the pressure gauge on my pop tester with one that will register to higher resolution, much more needle sweep in the desired range . Also from McMaster.

Pop Tester Gauge
 

I have a really large gauge on my pop tester, it's liquid filled too .

Time, patience and paying attention who what happens as you make tiny incremental changes is the key here .

Get some spare off spec injectors (most here have a bucket full of them) and tinker / play until you get a good grasp of it .

Hospital cleanliness is critical too .

There's a bit of luck involved too, every time the barrel gets re-torqued it becomes easier or fatigued losing previous setting.

My own preference is for balance between all six injectors, that way you can adjust timing with pump on 605/6's - 1 bar is difficult off the bat but obtainable with practice.

Deffo recommend larger gauge in the 110 - 150 bar range.

Injectors are art when you first try rebuilding them.
 

After a couple sets you get comfortable with being super clean and may even refine the process. Past that nothing is really uncomfortable, imo. Everything else is science. It's all cut and dry after you start thinking about the process and don't have to read about it anymore.

I swapped a 14000psi gauge for a 3500psi gauge to be more accurate with setting pop pressure.

This is why I dont bother rebuilding anymore. I just purchased 5 Bosch injectors and sent 5 injectors back as cores with fresh Bosio Nozzles because I couldn't be bothered with this fiddly nonesense. Two of the new Bosch nozzles were nailing so I sent them back for an exchange. Now the car runs perfect.


PS they came with a "lifetime replacement warranty" so when I want new ones in 50.000 miles I simply send them back.

The Bosch specialist here uses an electronic pop tester housed inside a large lathe type cover, still has to undo each time but the machine may take away some guess work with shim selection.