Thread Rating:
  • 0 Vote(s) - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5
Injector Pop pressure: whats safe and what's not?
TwoMuchBoost Offline

Posts: 16
Joined: Oct 2019
Location: NW Indiana, USA
Injector Pop pressure: whats safe and what's not?
My only real concern is not causing damage to my dieselmeken pump w/ 7.5mm elements. 

I understand that OE pop pressure for either of my engines (OM603 and the OM606 future swap) is 135bar(1950-2000psi) and that for big pumps and upgraded nozzles I've heard 150bar(2150-2200psi) is sort of the "gold-standard". Most notably for better spray/atomization when injecting more fuel in less time from a big pump. Most of what I've heard claimed relates to the difficulty of balancing the injectors with each other to a tight margin... it seems it gets harder and harder with higher pop pressure? BUT is there any actual dangers or simply diminishing returns and wasted effort? Reason I ask is because of current situation and lack of suitably sized nozzle shims.

Just bought a set of Firad SD 314 nozzles and a pop pressure tester to have a go at rebuilding injectors myself. All six injectors from the junkyard OM606 engine had poor spray patterns and leaked; what came out was SD 310 Bosch branded nozzles from France. While they did leak and spray poorly, the pop pressures for all of them were very close to 1950-2000ish psi.

After loading in the SD 314 Firad nozzles, pop pressure on the very first assembled injector dropped around 500psi to around 1400psi and was now opening even far below N/A spec of 1750. After adding the smallest shim I could find it bumped me up around 2800psi(190bar). After disassembling and sanding the shim down for a good bit; I ended up around 2600psi(180bar). How much further down do I need to bring pop pressures to be *safe* or can I give it a whirl like this assuming they will break-in and drop in pressure?

If anyone has a good lead on a suitable shim kit for these injectors, I'm actually in a position to where I'd purchase a decent quantity (not that BS kit on merc source that only has 26 and is over $40) as I've got several sets of injectors I'd like to rebuild. If 2600psi is a safe pressure though to where I won't cause damage then I'd like to try it just to see the difference if any. I understand it'll retard timing to a degree but it sort of nails at 8 degrees anyways so maybe it'll quiet/smooth it down some.
02-26-2020, 04:28 PM
Find Reply
zenins Offline

Posts: 22
Joined: May 2015
Location: Riga/Latvia
RE: Injector Pop pressure: whats safe and what's not?
Hey guys, can anyone please explain me what could be the problem of leaking injectors after rebuild?
My injectors were pretty bad and they were leaking (squirting) when pop testing - not all of them were constantly leaking but still they failed to pop properly from time to time. I decided to rebuild them with new nozzles from bosch.
I just have rebuilt them with new nozles but the I still have problems with them, couple of them are ok now but some are still not working properly... Everything is cleaned and assembled correctly in clean environment etc. torqued to 75nm. when pop testing some of them are still leaking and squirting, I cant figure out if the new nozzles are bad or there could be any other issue? I tryed to swap nozzles from working ones to bad ones and still get the same result with those particular nozzles...
This system looks really basic and I cant see any other cause of this issue, so please if anyone can point me to right direction - youre welcome!

p.s. - I decided to post here as I tought this might be revelant info and there's no point of making new thread. If not please let me know and I will post this elsewhere. Thanks!
(This post was last modified: 03-27-2020, 04:30 PM by zenins.)
03-27-2020, 04:28 PM
Find Reply
WSchotty Offline

Posts: 23
Joined: Nov 2016
Location: USA
RE: Injector Pop pressure: whats safe and what's not?
I am looking into the same thing right now. I just posted a similar question on my project post, may as well put it on here too.

I think we want to stay at 150 bar, but have no official confirmation this is where we should be with the superpumps. It will affect timing, not sure how it would affect pump life if you go over that, or if there is just a point where it doesn't open when you need it to at low flow.

I had a Bosch shop build mine to 150, I think they are already popping poorly as I suspect they used the India/China Bosch replacement nozzles. After only a couple thousand miles I'm getting cold misses and blue decel (not oil) smoke like the injectors are pissing. Also they are very loud, so suspect the 150 bar, if that is where they were set, has already slipped down quite a bit and I'm running more advance now.

I'll be interested to see how those Firads do, I'm looking to find out what the best nozzles are and where to get shims as it seems building and setting them myself may be the best way to go. Have heard both Firad and Monarch, but some are saying the Monarch have slipped in quality. I like things to be pretty closely balanced, and it would be nice to break them in and reshim again I suppose. Anybody go down this road recently?

Yesterday, 07:50 PM
Find Reply

Forum Jump:

Users browsing this thread: 1 Guest(s)