I was going back through everything just for giggles, and found this little head scratcher and think I have a plausible explanation for the lower ICP while hooked direct to battery. Battery voltage, on a long crank between the glow plugs and the starter pulling hard on the batteries I often see voltage drop down as low as 10.7-11.3. Loosing 2v in a 12v system will definitely make a difference in out put from any and all of the electronics. Of course no way to know if it's true but sounds good anyhow. So I can sleep easier now at least.

 

That makes sense. That was a head scratcher for me as well but then again, the whole ordeal kinda has been. What really makes me scratch my head is what would make a pump able to build great pressure but not volume? I mean its just a bunch of little pistons or plungers moving up and down on a swash plate. It was obviously capable of building 3000#+ of pressure based on my posted live data graphing but what component or set of components inside would make it drop off so bad under high IPR command? Even the gentleman from Mississippi Diesel Products was a little surprised by that and kinda questioned if maybe I had something else going on other than the pump. I basically told him everything that I've told yall as far as what I've done and what I've checked & replaced and he agreed that it's gotta be the pump at that point or possibly something gone haywire with the PCM. Said that it's a very unusual way for a pump to fail. As much as it doesn't make sense in my head, I'm just glad it fixed my problem. The truck is now the fastest 7.3 I've ever owned and one of the faster ones I've driven! Unbelievable how much of a difference it made. Must have been weak for a while and didn't notice it until it started getting real bad about a month ago.

 

Another head scratcher is how it was able to start so easily and quickly with such a sluggish and under performing fuel delivery system with a major aeration problem. Not only that but not even skip a beat at idle whatsoever. Ill loose sleep over this one for a while trying to make sense of it in my head.

 

Are you sure the 3000psi was accurate? Is it possible the ICP sensor was lying to you?

 

You have a point. While I'm not 100% certain as I don't have a physical gauge to tap into the oil rails with nor did I try a different sensor but I gotta assume it's reading pretty accurate because with the new pump it's giving me perfect readings for a healthy HPO system. I suppose it could be glitchy and that might also be an explanation for why it was reading 2300 psi with the IPR plugged into the trucks harness and 1700 psi with it hot wired straight to the battery

 

My completely nonexpert guess would be broken springs. They keep the shoe in contact w/ the swash plate and are basically responsible for the intake part of pump operation. So if the spring is broken you'll loose efficiency coming and going, as well as allowing the piston to float. So basically the pump wasn't worn out in the sense like you think of an engine . Rings are down to nothing and oil just blows by. The broken springs would be the equivalent of destroking an engine, took a 7.3 and made it a 5.0.

 

Forget my comment. I got lost somewhere along the way and thought you had changed the ICP sensor out.