Ok here we go....i have a 2000 ford f-250 7.3L diesel crew cab 2wd with 172,110 miles....when i start my truck up in the morning without plugging the heater in, the truck doesn't start up right away, you got to keep the key turned for a couple of seconds before it starts, then when it does start, it makes a kinda hissing sound from the engine and the check engine light comes and goes...truck runs fine when warmed up and the hissing stops, just like crap when cold....took it to the ford dealership and they replaced the module for the fuel injectors....truck was fine a for a couple of days but starting acting up again so i brought it back to ford, now there saying that the #8 cylinder is weak, what do you think???? When i keep my truck plugged in all night and start it in the morning, everything is fine and no hissing from the engine but the check engine light still comes and goes....so does anybody have any suggestions????

 

I would start by checking the glow plugs individually, do so by pulling each one out, starting with the #8 cylinder, and connect the wire back to it, and ground the plug to the engine and turn the key to see if it glows, if it doesnt, check for voltage at wire, if required voltage is present, replace defective plug