PeachParts Mercedes-Benz Forum - Injector problems

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Diesel911,

so you are saying the fuel is coming up past the threads and out onto the base of the injector? So that means that the threads are not sealing, right? From dirt?

I would suggest that you take your truck in a mechanic, tell them about your injector. Mine did the same thing but the mechanic just dropped some injector cleaner and it works like magic! That very simple fix just cost me a buck so better bring it there and let them check it.

Quote:

Originally Posted by 1975300D (Post 3332294)

Well, I got my fuel injectors reassembled, but unfortunately, three of them leak.

I did the lapping procedure and I also made sure they were nice and clean. I also blew them out with compressed air.

Yet, two of them at least are leaking at the return nipples and three are leaking at the body joint.

Will these leaks tend to seal themselves with time?

Since the nipples are not serviceable, does that mean a new fuel injector is required?

Also, one other problem. There is no fuel coming from the No 1 line. I removed it to blow compressed air through it and it is clear, there is fuel at the pump end, but no fuel comes out the other end. :confused:

Thanks

Mark

If your return nipples move in any way they will leak. Additionally you may have a leak between the upper and lower injection bodies themselves which may or may not be noticeable in the pop tester. If the heat shield is not new it will likely also leak and that will affect the engine compression. A leak at the injection hard line should be clearly visible.

Quote:

Originally Posted by 1975300D (Post 3333020)

Diesel911,

so you are saying the fuel is coming up past the threads and out onto the base of the injector? So that means that the threads are not sealing, right? From dirt?

I am not sure which particular threads you are speaking of. However, no sealing is done by the threads. Threads used on Bolts and similar items actually have a lot of clearance between them and they are not made to seal. That is why Crush Washers are used on Bolts to seal and why on Pipe type threads there is a taper (in hopes of sealing).

When you assemble the Injector Nut and Upper Body of the Injector the sealing is done by the precision fit of the Parts inside of the Injector.
Dirt and even Rag Lint between the Precision Surfaces inside of the Injector can cause a leak.
Dirt in the Threads of the Upper Injector Body or Injector Nut can cause the Torque to be off and that can cause a leak.

When you screw the Injector into the Engint the Sealing of the Combustion Gasses is done at the Heat Shield against the Injector Nozzle. Dirt between the Heat Shield and the Injector Nozzle can cause a Combustion Gas leak.

At the very top the Fuel Injection Hard Line is sealed to the Injector by way of that cone shaped tip fitting/wedging into the inverted cone shaped opening at the top of the Injector. Dirt between those surfaces can cause a leak.

If Fuel is coming up from below the external threads on the Injector that is most often Fuel that has leaked down into that space I indicated in the diagram.
The exception would be If the Injector Nut had a crack on the side.