Ok I have a 2000 7.3. Recently installed new batteries, glow plugs, and GPR. Ever since when I go to start my truck after it has been sitting overnight the battery gauge when the ignition is turned on waiting to start it jumps to about 10volts. Then slowly creeps up to about 12. If I dont wait forr it to get up to 12 even though wait to start light goes out prior to that , it will not start. I will wear battery down if I dont wait. ANy ideas.

 

Just a shot in the dark but sounds like the alternator is on its way out.

 

Take the batteries back to where you purchased them and have them checked and also have the alternator checked, but it sounds like battery problems. Could also be the battery connections, make sure the are clean and tight! Use some dielectric grease on the terminals.