Alright guys I have a 88 7.3 idi I bought recently from a co worker they had the truck for almost its entire life so far and never had any major issues with it. It will not cold start but will start everytime after the block heater has been plugged in for a while. I have replaced the glow plugs and have also replaced the glow plug relay. I have done the cycling the glow plugs to allow them to get warmer to attempt to start it and it fails everytime the motor is cold. If you plug the block heater in for a half hour it will start kinda rough but its been about 18 degrees the past two weeks. I want to have confidence that I can take it to work and let it sit and know it will start. So can you guys please help me out?

 

check your battery terminals and cables, make sure your batteries are pumping enough juice to the starter. if the starter is turning slow then the motor wont turn over fast enough to build the friction in the cylinders to start it. if thats not the problem then its probably a fuel issue. if it isnt the batteries/cables/terminals then start with the return lines, bleed the fuel system, if that doesnt help then could be IP.