ot1

OM 648
I had black death in two cylinders, so I pulled all the injectors cleaned everything up, numbered the injectors as I took them out. Some were very dirty so I decided to take them apart, clean the nozzles and obtain even spray when pushing the cleaner pipette inside the nozzle. Ordered all new nuts. Of course new washers and hold down bolts.
Got rid of all the black death with Valvoline Carb and Throttle Body cleaner, long wooden Que tips to clean seats, reassembled injectors. Cars runs great ~193K, easy to start now (ambient temp is now 40 F to 60 F). But I have pooling of diesel fuel in the injector wells. I cleaned up the fuel because it was quite a bit and I didn’t know which injectors were leaking idled it for over 30 minutes and all seemed well. But now after taking it out on the road the second time I see which injectors are leaking 5 of the six. Unfortunately it is not coming from the inlet nuts because I put blue paper towel around those connections and they are dry, except one is weeping from the male side of the injector line.

Anybody here disassemble their fuel injectors?
So I suppose its leaking from the nozzle nut connection pushing unused fuel up the well. Was I supposed to use a sealer on the threads? What should the torque value be on the nozzle nut?

kajtek1

I have hard time to visualize where your leaks are coming from?
If you did not take injectors apart, the only option is HP connector, or leak lane.
HP connector can be cleaned and retorqued.
Leak lane might need replacement.
Generally you can use Teflon dope on HP fittings, but that should be last resort.

B34chBum

I can see only 3 possibilities:
- The HP rail connection
- The leak down / overflow line connection
- Somewhere out of sight on the body of the injector ("So I suppose its leaking from the nozzle nut connection pushing unused fuel up the well")
Of these, the third seems the least likely, and you've covered the first one.

I didn't see you mention getting new o-rings for the leak down lines - did you replace them?
They tear and/or get pinched removing/replacing the return line, and old ones get hard and inflexible.

ot1

yes installed all new orings on the return line fittings at each injector. FCP has a kit which includes those orings and the bolts and washers. But I will check that by wrapping blue scott towel around those lines to make sure its not leaking from those.

has anyone disassembled their injectors? Does anyone know of an Bosch manual for injectors? The nozzle nuts have a very fine thread.

kajtek1

Stil remember the plastic fuel lines on OM606 engine.
Replacing orings on them had very low success ratio, as plastic seats deteriorated as well and small orings were easy to stretch.

ot1

maybe you already know but the fuel return fittings on the top of the OM648 injectors are metal, looks like stainless.

I pulled and disassembled and cleaned (Valvoline Carb cleaner works very well) the #1 injector yesterday, used Vibra-tite 567 on the nut threads, just doing #1 for now, couldn‘t find a torque spec, so I did 40 nM. see if this stops the fuel leaking. The hold down bolt torqued to 7nM then +90 and +90 Degrees = 180 degrees, comes to 20 nM.

according to my scanner there is 5000psi in the rail at idle, and it shoots to over 10,000 psi @ 2100 rpm

ot1

ok I still have the leak after redoing only #1 injector. So, I am going to do a lap of nozzle as found in a Youtube vid with #2000 grit, My leak at the top of #1 is fixed.
also a comment was 70 nM on the nozzle nut.

ot1

Ok I pulled #1 injector last week, polished the nozzle surface and mating part on the injector with #2500 grit on a machinist granite block. Polished bright, reassembled and torqued to 70 nM, 400 miles later still no leaks, even getting speed up to 95mph.

ot1

yes it was the third option, least likely, because the white ceramic grease coating the outside body was completely gone when I pulled the #1 injector 11/10/2023.