I have a 1996 gmc 2500 with the 6.5 diesel. last weekend it shut off on me, I drifted to the side of the road, cranked it over and it restarted ( took a little longer than normal though) I got a code po251 and a code po370. hence I thought it was a fuel delivery problem. once I got home I put in a new oil pressure sender and a new lift pump. bled the system using the "t" handle on the front of the motor. tried to start it and it just kept cranking, but tried to start after 20 seconds or so. as of now I am at a loss! did I not bleed it enough?? had all but a full tank of fuel, new pmd recently, new "ops" and new lift pump. one other thing I noticed is my tank seems to hold pressure..as in when I go to remove the cap I have to bleed off some air first. any help is appreciated as ive about had the sh*its with this thing!

 

Try bleeding at injectors hold petal to the floor and crank. Although the lines should bleed them selves it could have to much air in system. Although I don't think lift pump was your problem to begin with. Check your lines before ip and after will help narrow down the issue. Also did you did you check your filter and prime the filter houseing

 

checked the boot in the tank (attached to the sending unit) looks good, steel lines on unit were so-so. bled the filter then bled the "t-handle". truck started up and had no problems! started it up several times within an hour or so. after about 2 hours I tried to start it and it was hard to start and threw the same codes! im thinking air leaking in somewhere....thought id go ahead and put another sending unit in with new hoses to the frame rail. the steel fuel lines on the frame rail were obviously replaced before and look really good!

 

after sitting for a day....I bled the fuel filter and the "t handle" and got no air out what-so-ever. also tried holding the pedal down. tried to start the truck and it was hard to start and threw the same codes.

 

installed a brand new injection pump, made sure it was timed ok, bled the entire fuel system. tried to start the truck and it does the same as before....cranks away, throws the same 2 codes and after a little cranking seems like it wants to start but it wont! anyone have any ideas????