I am fairly familiar with this engine and what not. I have a 1993 3500. I rebuilt this engine and rebuilt the trans and put a new injection pump in it not to long ago.




So here is my problem. The truck runs and drives really well in town but when i get it on the high way it does not want to go over 65. I know my lift pump is working correctly. I have the upgraded relay wire harness to bypass the OPS Lift pump problem. I am getting what seems to be good Volume to the IP, I checked all the lines the best I could for loose hose clamps and what not being loose and sucking air. I have a boost gauge and im getting a healthy 5 psi on my gauge going down the highway. I don't know how accurate this is but it has always read 5 when it ran just fine. I got this injection pump from Pensacola Diesel probably 5 months ago. I did notice today that one of the injectors is seeping a bit but that should be due to the fact that its a defect because the injectors in this truck are not but a year old and don't have 15k miles on them. The pick up screens in the tank have also been replaced recently as well along with a new fuel filter. I also made sure the air filter is clean and it is.. Im going to replace this leaky injector and see what happens but I have a feeling it will not resolve the issue. I have a bad feeling its sucking air... Do you have any advise for me? I appreciate anything you can tell me. This truck helps me earn a living and i need to get it fixed.

 

from everything i am ready 5 lbs is a sure indicator that the lift pump is garbage. and you know you can buy faulty electronics at any time.
hell it could be junk right off the shelf.
but then again. im learning the diesel life myself.