AMBAC PSB 6A 100 series fuel injection pump

[handytravis]

I have a AMBAC PSB 6A 100G series pump on a 1963 Allis Chalmers HD11EP dozer with the 11000 series BUDA motor. Sent pump out for rebuild, and tested on the stand perfect- no issues. I had to leave town so I had my brother install it- he fought for a long time chasing air until I had him fill the tank with 55 gallons of fuel for head pressure. Fuel flows out the supply pump into secondary and flowing good into head, but nothing coming out of the injection ports on the top of the head (all lines removed) and flow is coming out the return line. I can't figure out for the life of me what the issue is besides maybe a stuck delivery valve in the head causing the fuel to bypass the high pressure side of the head? He was bleeding the pump from the plunger bore cap and actually removed it all the way one time when he was chasing air, but put it back on with about 55 lbs of torque. No fuel in the crankcase, A guy looked and said it doesn't look like the transfer pump is making enough pressure, he estimates 4-5 psi, but that's out of a larger hose. I know I need to test that PSI out the transfer pump but I think when it gets necked down in the head, the pressure increases like putting your thumb over a garden hose right? Could it be supply pump pressure relief valve? Any Ideas?

 

[MikeJM]

I know its a silly question and a simple thing at that. But the transfer pump is hooked up in the correct direction? Saw it happen on a model 100 once.

 

[handytravis]

There are no silly questions here- at one time I thought that the lines could be reversed, but it is hooked up correctly with the flow. Thanks for thought!

 

[MikeJM]

I reread your first message. Fuel out the return so the plunger should be moving fuel.

The only thing I can think of is the metering sleeve on the plunger isnt in the right spot on the control and not in a position to pump fuel. But pump shop should have caught that. Then again its not the first PSB back from a pump shop Ive seen that wouldnt start.

Did the plunger move up and down when he had the plug out?

 

[Dieseltech]

Five PSI is enough for the PSB hydraulic head to work, but some systems do use 20-25 PSI relief valve setting. I don't understand why head won't bleed with lines off if pump past low speed cranking delivery on the stand..