Diesel Doctor

ok so i just bought a 94 2500 6.5, 18k on the motor, id will start fine cold but not when hot i have to wait till it cools completely down, pmd is still on the ip and will be replaced later this week, the ip looks new,lift pump dont work that will also be fixed later this week, even tried pourin water over the ip to cool it down, works sometimes but not all the time check engine light is on codes are 88,67,68,87. which also brings up the other problem it doent like to shift into O/D dont know why that is either,im sure im forgeting a couple things any thoughts? just hopin its not the ip,

Fix the lift pump first. then make sure there are no leaks in the fuel lines to allow air in. Make sure the fuel cap is correct, holds a slight pressure but almost no (< 2") vacuum.

The trans codes could be due to a bad speed sensor. More info is needed. Look up the troubleshooting procedures for those codes. Start with the lowest number first.