D8 transfer pump

Simplest thing you can do on an old CAT with single line to fuel tank is get a piece of an inner tube from a tire shop and a hose clamp. You want a piece with the stem in the center of it, large enough to clamp over the fuel tank filler. Pump it up with a hand pump or other source of compressed air and then open each fuel bleeder in turn as you work your way through the system from filter to injectors. You only need to pump it up enough to bulge the rubber out tight, that will easily push fuel through the system unless something is clogged.

CC, does the transfer pump need to be turning or can the fuel be pushed all the way to the injectors without turning the engine?

There must be enough clearance in the transfer pump to allow fuel to flow through and bleed the system. Most of them will eventually bleed with only the static pressure of a full fuel tank, the pressure of the inner tube speeds things up dramatically.

If you can turn the engine over even a little, with the positive pressure of the air at work, that should immediately expell any air.

The other good thing about pressurizing the tank is you can find any suction leaks which may be letting air into the fuel system. Sometimes the fuel line will have loose ferrules or cracks etc that don't leak fuel very fast, but can still admit air when the pump is running. With the single pipe fuel system, there's no place for the air to excape, so even a little leak can be a problem.

Thanks CC and others. I had already tried pressurizing the tank. I tapped an 1/8 NPT thread in the vent hole of the cap and put a pressure regulator on it set to 10 psi. I got fuel to the transfer pump and over to the fuel cooler but that is all. I took the 1/8 pipe plug out right next to the fuel pressure gage and got air!(?) I then realized that the return line to the tank must be above the fuel level in the tank so I guess it would be pushing pressure the wrong way. I then plugged the return line and still no luck. I took the filter cover off and with air pressure on it won't even push fuel into the filter housing. The old girl was running great when I shut her off in the fall so I'm a bit lost. I guess something is plugged or the transfer pump is bad.

Did you check the cross over valve used to charge the torque converter. If it is left open the transfer pump just pumps in a loop by-passing the fuel filter housing.

Thanks OM, that is a very good point. I will pursue it.

is a vent tap on top of converter too

Thanks Mervyn,
This brings fond memories of New Zealand. I started three new sweet corn harvesters in Gisborn in 1978. Trained for a few days and then we did a "walk about". What a beautiful country!