450B wont stay running unless...

Hello everyone and thank you for reading my post. I am having a great deal of trouble with a 1980's 450B dozer. It was started and used to pull a semi out of a ditch. It ran for about an hour and a half, pulled the semi out, mowed down a few trees, and then on the way back to the barn it died in the middle of the field and would start back up but not stay running. The fuel system has been bled multiple times at the filter, injection pump inlet, and the four lines at the pump leading out to the injectors. The tank was removed because it was filled with sediment and rust. Currently I have an auxiliary tank on it. I found a leaking on/off valve for the tank and had it replaced along with the transfer pump. However, even after bleeding it with the aux tank, it still starts and dies after awhile. If I let it sit for a day, the first time I start it up it runs for a whole minute just fine. Then it progressively runs for less and less time. I've pulled the inspection cover off the side of the injector pump and saw no debris. I found out yesterday that if I crack the screw on the side of the injection pump and allow fuel to leak out of that hole, it will stay running with no issues. (Other than polluting the dirt). It's almost like it's over pressurizing, and cracking the screw on the pump relieves the excess pressure. I've blown out all the lines with compressed air and re-bled them. I do see a bit of 'aerated' fuel coming out of the 4 lines leaving the pump if I crack them (could just be high pressure), but cant seem to bleed it out. If air in the pump was the issue, it doesn't make sense to me why cracking that screw on the side would resolve it. Has anyone ever had this issue before?? It's driving me nuts. I want to pull the pump but my boss doesn't want me to get into that yet. Pics below. Thank you for all advice!!

It sounds like the internal housing pressure is exceeding charge-fuel pressure that causes high-pressure fuel to stop. Common problem in
that pump. Return fuel circuit it likely plugged.

The steel fitting on top of your pump where the return line hooks up is the "housing pressure regulator." Likely it is plugged. It is
supposed to keep internal housing pressure at less then 10 PSI. When it plugs and internal pressure gets up to 60 PSI, high pressure fuel-
charge creation stops. I have driven many a tractor home with that fitting removed and fuel dribbling on the ground.

I already tried removed that top fitting, as well as where the other end of that line connects to a rubber hose that returns the excess fuel to the tank, and blew them out with compressed air. unless the clog is inside the pump, then that doesn't seem to be the issue. My first thought was clogged return line....Wait, okay my brain just started working. I'll be right back.

Okay so I only pulled the line off and blew it out, not the pressure valve. Just did that an viola, I find the glass ball I've read so much about. I was looking in the wrong place. Theres a bunch of crud in this valve and the spring doesn't seem to be working. Just cleaned it out and it's good to go back on now. Thank you good sir! I believe this will solve my problems. At least temporarily until it gets clogged again. I just got all the crud out of the tank so perhaps I should replace the filter. Hopefully none of the seals are deteriorating in the pump, we shall see. Thanks again!!

(quoted from post at 08:29:45 04/05/18) It sounds like the internal housing pressure is exceeding charge-fuel pressure that causes high-pressure fuel to stop. Common problem in
that pump. Return fuel circuit it likely plugged.

The steel fitting on top of your pump where the return line hooks up is the "housing pressure regulator." Likely it is plugged. It is
supposed to keep internal housing pressure at less then 10 PSI. When it plugs and internal pressure gets up to 60 PSI, high pressure fuel-
charge creation stops. I have driven many a tractor home with that fitting removed and fuel dribbling on the ground.

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The weight retainer ring inside the pump is failing, that's what is plugging the return check valve fitting with what looks like coffee grounds. You can confirm that's what is happening by running the engine with the two screw timing cover loose on the pump side. Should run fine while the fuel leaks from the cover. Keep cleaning the fitting, and it will run awhile, UNTIL the weight retainer pins shear off, seizing the head rotor, and breaking the drive shaft. Get really expensive when that happens. Best get the pump serviced soon before that happens. Had an IH 806 pump it happened to last summer, luckily I had a good used hydraulic head on the shelf.