986 injector pop off pressure

Mgdoug3

New User
I'm currently overhauling a 986 that had a cracked sleeve. While the head is at the machine shop, I pop tested the injectors. They all popped off around 2500 psi. The atomization seemed to be less than ideal.

I have a manual for the 400 series block and it says 3600 to 3750 for new and 2900 used for the 66 series. It doesn't mention the 86 series. I'm assuming the pressure is the same but I'm not positive.

I know my injector tester is good because at the same time I tested some injectors off a JD 4250. They popped off within spec and had a great pattern.

Can anyone confirm my manual is correct? Thanks for any help.
 
Use the 66 book, injectors are the same. I try to set used spring injectors opening pressure 3100-3300 range. Hope you have the injector clamping tool, or you WILL break the locating pins..
 
Thanks for the response. I don't plan on rebuilding the injectors when a reman can be found for $45. The tractor isn't mine. I suggested injectors to the guy but he responded with "but it was running fine before." I drained out 7 gallons of water and oil.
 
I remembered I had an old injector a
mechanic gave me to install the injector
cups years ago. I put it in the toolbox
in case I needed it again.

I was told the injector was no count so I
decided to take it apart. It was fairly
easy to do. Only thing wrong was the
needle was stuck. After freeing it up and
disassembling and cleaning the rest I
stuck it back together.

The injector I been using to install
injector cups and after years of being
lost in a toolbox, popped off at 3600 psi.
It's better than any injector that came
out of the 986. They ranged from 2300 to
2600. I'm still trying to convince the
guy he needs injectors.
 

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