It sounds to me like the engine has a mixture of old and new type glow plug system fitted. That will not work properly, so either put it all back to original or convert it properly to the parallel glowplug system.
Undo one of the unions onto an injector and crank the engine over. Fuel should come out. If not, then check that fuel is going to the fuel injection pump by removing the fuel inlet pipe to the injection pump. Crank it over. Loads of fuel should come out. If fuel comes out, then it looks like there is a problem with the fuel injection pump. Check to make sure that the engine cut out lever is not jammed. If that is good, then the injection pump needs to be overhauled. If no fuel comes out then, the fuel lift pump could be broken or the pipes blocked or damaged, or even no fuel in the tank:doh: