Good morning,
Thanks for responces concerning my previous problems,now I've got a new one.Ever since I changed the glow plug relay I get a surge like I'm stepping on and off the pedal.Also when I start out from dead stop,the engine speeds up and I haven't given it any more pedal.If I tramp down on it,it takes off like nothing was wrong,then when I'm going 45 to
55 mph,it starts to surge again.We were careful not to disturb any wire connections and the fuel filter has been changed recently.Any suggestions would be appreciated.
Thank you

 

Replace the IP fuel return line with clear diesel rated tubing and with the truck parked safely idling watch that line for bubbles.
Bubbles indicate air getting in the fuel system.