2012 Isx 2350 475 with codes 4726 and 0559

[ahrenbenjudah]

Ok. Removed the fuel pump head. The barrel springs and retainers look great. The tappets and rollers are perfect. The camshaft is great too.

It has the asymmetric steel plungers and those look good too. The only thing I noticed was that the front plunger remained pushed out of the barrel retainers. Like I could push it in and it would push back out. However, the rear one I had to pull out by hand and if I let go it would slowly drop back all the way in to the barrel.

Following the Cummins test of blowing air in to the inlet of the head, the plungers both extend. But as soon as I remove air, the rear one sinks back in to the barrel.

Not sure if any of that is an issue but it seems that maybe it is. I’ve only ever had issues with the ceramic plungers getting chewed up and being the obvious culprit.

What do you think?