I replaced my 6 injector nozzles with new Monarks in my 87 300TD. I'll jump straight to my most important question before I get into the details of my other concerns. The numbers stamped on the side of the new nozzle holders are all identical (525 MDN, 39 305 128, and 0SD 265), but 3 of the nozzles have a wider spray angle than the others. One of them is quite a bit wider. I would say the angles range from 5-20° (this is just a guess, and 20° might be a stretch). I had this observation confirmed by a local injector shop. The atomization is all pretty uniform and the pop pressures are all between 2000-2075 psi. My question is whether or not the spray angle makes that much of a difference in efficiency of burn? Does the prechamber ball pin allow for some variance in the angle? Is the pop pressure (thus timing) and atomization more important for efficiency of burn than the spray angle?

I pop tested all 6 injectors before attempting to clean and rebuild them, and made notes of any oddities (#6 was a good 150 psi under the rest, and #5 was frequently streaming or "peeing" before the pop). I took them all apart and soaked everything very carefully in carb cleaner (from a can, not the spray kind). Everything cleaned up well. I followed all the precautions I read about here about keeping the parts separate and being as surgically clean as possible. I lapped the mating surfaces with 2000 grit sandpaper on a pane of glass. I blew the internal parts dry with air, lubricated in clean diesel before reassembling, etc. (I'm skipping some repetitive cleaning steps here for brevity). When it came time to install the new nozzles, I slid them directly out of the container they came in, directly into the lower injector half. I never handled the new nozzle holders and needles…

However, after everything was back together, I was having issues with 2 of the new nozzles streaming before the pop pressure was reached. It was intermittent, and sometimes I couldn't get them to do it, but with enough pops it would happen again. So I swapped those 2 nozzles into different injectors that seemed to be spraying fine and the problem repeated itself. This confirmed that the nozzles were bad and I was able to get replacements. However, I was also very rarely getting some streaming from some of the other injectors. It was very infrequent, and if I stopped testing for the day and tried again on another day, I wouldn't get the problem at all. I have opened the injectors back up and noticed that some of the nozzle needles don’t move smoothly in the nozzle holders - it feels like there was some invisible grit in there, even though the needle had not previously been separated from the holder. The only way grit could be introduced would be from the inside of the bench tester, or possibly if the filter I used for the diesel fuel wasn’t fine enough. I think my next step is to clean any rough feeling needles. Any tips on how to best do this? Diesel? WD40? Carb cleaner?

Any tips and insights are, as always, greatly appreciated!