I have a 93 f450 with a 7.3 non turbo and it will not start up.
it takes cranking on it for too long to start and I can kill it right away and it restarts fine
Things i have replaced...the lift pump and all orings,the return lines and all orings,all check valves on the fuel return side and even pulled the tanks and re oringed all the lines there but now I,m stumped,the gps is working great...HELP

 

if you have more than 1 or 2 glow plugs not working it will start very hard. you can check with a test light by hooking to the positive side of battery and touching the light end to the glow plug terminal once you unplug it. if it lights it is good if no it is bad. then check to see if you are getting power to the glow plug connector by hooking to ground with test light and have someone cycle the key if you get light circuit is good.