yep your right there are pretty cheap, $63 for the D6 ones i believe.  i still havnt had a chance to actually see whats going on as i pulled the transfer pump off and am waiting for a seal that was leaking.  thanks for all the input guys, ill post again when i make some head way.

so has anyone ever had an injection pump that was worn or cracked causing #6 to suck air causing it to act like an air compressor when i crack off the fuel line on the injection pump ? i got the cat running finally but when i loosen number 6 line it doesnt bog down at all like when i loosen any of the other lines. that tells me number 6 is not firing at all ? i have changed the little internal plunger pump assembly, ive tried swapping around injectors, nothing changes. we also had the lift pump apart also no change. we even tried a second complete injection pump off of another 9u and still no difference, which i think means that both pumps have the same issue whatever the hell it is. Im getting really frustrated, and i guess my next option is to take the injection pump in to union tractor and have them bench test it. any ideas ?

from what i read and if i understand correctly i would advise that your problem is with number 6 cylinder and not the injection pump.

Hi Team,
if after changing injectors the problem still exists then I would next look at the pre-chamber seat for the injector--if you have renewed the pre-chambers in your overhaul then I would next suggest to change out or swap No 6 pre-chamber to another location and retest--Your symptoms are still of a non seating/sealing injector valve thereby allowing compression gases back into the injection pump.
Hope this helps,
Eddie B.

You were right, i pulled the line completely off of the injection pump for #6 and its pushing compression out the line towards to pump.  Can you explain to me how it could do this though, is there not a valve in the injector itself ?

Hi Xtremist,
indeed the capsule injector nozzle has a valve in it that when not damaged or has crud on its seat can and does hold back compression and combustion pressures.
If it is not seating then the pressure can easily push back past the injector nozzle valve and enter the fuel line down thru and past the injection pump's one way check valve, that should stop the gasses passing but for some unexplained set of circumstances the gasses do pass this check valve, I have seen it and been told of many times by clients when I worked in the Dealer Injection Shop.
Only explanation I can think of is that the check valve is open during the injection pumps pumping action and so the higher cylinder pressures force back past it at this time--I stand to be corrected.
Sorry at this time I need to change computers to give you sectionised views of the capsule.
Cheers,
Eddie B.

ok im still alittle confused here lol....is there an issue with the injector as well, im not quite understanding how the precup can cause the gas to flow through the injector itself ....?

There are two possible events causing compression leak back.
1. The injector nozzle is defective in that the internal check valve is not seating.
2. If the capsule itself (injector) body is not seating in the the pre-combustion chamber compression can leak back by passing the capsule.

The nozzle nut may have been over tightened also and damaged the nozzle.

the nozzle from 6 works fine in 3 cylinder, but swapping nozzles changes nothing in 6. so if it can leak back ill try a precup next.

thanks guys !