2008 chevy k5500 4x4 cc

OKAY I AM NEW TO THE FORUM. I work for an electric company that beats the piss out of their trucks fyi. I currently have a 08 top-kick 5500 4x4 with issues. So it had a P0087 code for low rail press., so it went to the dealer and they changed the fuel filter,fprv,fuel tank lines. The truck was d-rating itself and having low power issues. So the dealer said it needed a CP3 because they were commanding 26106.7 psi and only getting 23931.2PSI which to me is with in spec. so they claim it idles just fine and you can drive it short trips and its fine but once it warms up and/or goes under a load the truck looses power and on goes the MIL lamp.. I don't believe it is a pump issue......if any one has any input i would appreciate it greatly as the dealer has us over 6 grand in this damn thing. Bal. rates are +-1.2, fuel tested at 37 API

Run with the fuel tank cap slightly loose, so it can't hold vacuum. See if that helps. A problem with the cap's vent can cause excessive vacuum. A diesel fuel cap should vent at pressures above 2-psi and vaccum at 1". Caps are cheap. Don't use a gas cap.

If that's not it, have someone measure the vacuum at the fuel test port on the engine to determine whether there is a restriction in the fuel supply.

What's the history of the fuel injectors? Worn fuel injectors can bypass enough fuel that the CP3 can't keep up with it.

Hot fuel becomes thinner, and makes these problems worse.

Let us know.

Jim

Truck has 80k on it with stock injectors, i believe it has a non-vented cap on the steel tank.

If the previous suggestions don't help, spending some time in the following P0087 thread should help.

http://www.thedieselpageforums.com/t...ad.php?t=35292