I got a 6.5 2500 maybe 3 months ago 150,000 miles and this is my first diesel so please help.......

I jumped in it let the glow plugs cycle around 2:30 pm 50 degrees out. I d rove to gas station(1 mile) then shut it off went in and paid came out sat in truck while pumping and noticed my glow plug light was on with keys out and truck off. I started it after fueling and moved it bout 30 feet to parking spot( it was shaking and making i slight tapping noise never happened before). i talked to a guy on phone he said it might be injectors. another said it could be GP tip broke off sitting in cylinder. well i drove it home and it stoped tapping but glow light was on so stopped and got lucas injector cleaner and removed glow plug 10 amp fuse(light was still staying on) i drove home let it cool down a little then started up and acted fine so i put fuse back in and lights came on and stayed on again. then this morning it wouldnt start at all just cranking over, sprayed starter fluid in it and it fired up. im selling it friday and want to fix it before. ive looked over wiring diagrams and i cant figure it out so someone please help!!!!!!

 

Welcome to DB to help you we need all the Info we can get otherwise it's a shot in the dark,As for as using starting fluid in a 6.5 you should never ever ever use it in these engines or you will be picking up the peices that hit the ground starting fluid and the 6.5 =disater,OK now fill out and copy and complete the following checklist and we will do our best to help you
Diagnostic Checklist version 2.0 [10-2009] - Diesel Place : Chevrolet and GMC Diesel Truck Forums