Dan,
These Chinese tractors are notorious for having a handful of hidden filter screens throughout the fuel delivery system.. the first is in the fuel tank, part of the outlet from the fuel tank. You need to drain the tank and then remove the output plumbing to get to it. Of course, clean the tank while you're at it.
The next one is at the inlet of the sediment bowl, as I recall. It is inside the fitting where the line from the tank attaches to the sediment bowl. There may, on some tractors, be another one at the outlet of the sediment bowl, again, inside the fitting.
Some tractors have a spin-on canister filter after the sediment bowl, and there is often one incorporated into that assembly somewhere, though not always.
Next, there is usually one at the banjo fitting where the fuel line enters the lift pump portion of the injector pump assembly. The banjo fitting is at the point where the fuel line connects to the lift pump - it is shaped like a banjo, thus the name. You pull the bolt that goes through it and you should see the screen under the banjo fitting.
Chinese tractors are also notorious for having rubber that deteriorates quickly in the presence of ozone, ultraviolet light and maybe even bad karma. Anyway, the inside of the rubber fuel lines can become weakened and/or deteriorated to the point where the line collapses internally under suction and shuts off fuel flow, (like sucking on a soggy paper straw) or bits of the lining clog up one or more of those pesky aforementioned screens.
Have you opened the injector lines at the top of the injector pump to see if there is fuel there? Did you open one of those lines when you were trying the priming pump? Did the priming pump develop resistance to being pumped, indicating that it had filled the lift pump to capacity?
As I've already said, these injector pumps are really fairly robust and rarely die. Far more often the problem lies in fuel delivery to the high pressure side of the injector pump assembly, caused by dirty fuel or lines, clogged screens, collapsing rubber lines or diesel bugs clogging everything up. If you have ever had any brown or black sludge in the bottom of your fuel tank, suspect diesel bugs and take all the drastic measures necessary to deal with them. Those little suckers will not only plug things up, they will actually corrode the metal parts of the system, necessitating replacement of more expensive parts.
Well, there's a run-down on what is involved int he fuel delivery system and the sequence to use in checking it all out. Be sue you've ruled out all the simple possibilities before ordering a new injector pump, unless you just have money to burn.
