If you think that you may have a clogged tank filter, before messing with the tank screen, try some Startron enzyme with breaks up the diesel slime into burnable sizes.
I have a ready flow from the fuel tank. While primer pump leaks while in operation, it fills the filter with a few strokes and the clear filter gushes nicely. I thread it back down and no more leak. I found a small leak at the rear injector. I cut off the return hose and reinstalled it and now that is dry.
Yesterday, I continued my quest for fuel restrictions downstream from the pre-pump. I dismantled the filter housing and cleaned all of the banjo fittings. The only thing that was at all awry was the tiny bleed hole from the top of the filter area to the return was partially blocked and I cleaned it with a piece of copper wire. The insides of everything is black. I added another bottle of cleaner.
I put it back together and with a little extra cranking and wobbling around, the engine picked up all four cylinders and idled nicely.
I was very disappointed when I tried to drive it. It had less power than ever. I could barely get it up to 40 mph on a level. The strange thing about this lack of power is that the next time I run it, it will be normal, with beaucoup pep. I have never had it lose power once it is running right, but once in a while it will gradually give me my power back. I wonder if the fuel flow governor is sticking.
The hard starting is very predictable. The glow plug relay seems to be working fine now as the light comes on every time. Perhaps the ignition switch was intermittent from lack of use. But I crank for 10 seconds, 10 seconds, then the third time, it stumble starts. It's as if the injection pump has trouble reestablishing flow to the injectors.
I think this car had years of neglect or it sat for a VERY long time. A shame, because the body and interior are in such good condition. Once I get past this problem, it will be a great car.
-- Mark L. Bardenwerper, Sr. Technology...responsibly, thoughtfully