I've got a buddy with a '92 D350 ext. cab 5spd. It's very hard to start on cool not even cold mornings and any other time it sits for a while during the day. He said that even when it's plugged in over night it makes no difference in starting. We freshened up all the filters and changed the oil and that didn't help any. Could it possibly be the grid heater is out?

 

Check your Grid Heater. What you mean by cool morning? Could have a fuel leak that is allowing air to seep in overnight making it hard to start.

 

Cool morning like less than 60* i will have him check the fuel lines.

 

Hes got a fuel problem it sounds like I have a 93. when its around 20 you dont have to wait for the wait to start light to go out. turns over slow. but I would first put a fuel pressure gauge on it. then go from there

 

Yeah sounds like a fuel problem. Most lickly air in the system leaking in.