Have you replaced the nozzle and fuel filter? Check for kinked fuel line? Did you use diesel rated fuel line? What is the voltage at the unit when running? Did you replace all of the wiring? Is the exhaust clear? Any errors?
Replace the fuel line with good quaity diesel rated. Run the filter input and return line to a can of fresh clean diesel and if you still have the problem then it's not the fuel. Get input from a good AH person like Roger Burke. It's certainly possibe that you controller has gone south.
