Ok, when run'n D2, coming up to a stop light/sign...etc, when downshifting or just throwing in N, the trucks' rpm will drop to 500ish, then back up to its respectable range, BUT when run'n on WVO,..(which the feed lines are plumbed to the p/s front, d/s rear ports), coming to a stop...etc, the rpms remain the same? wvo pump is a steady 75psi, where as the D2 f/p gauge seems to fluctuate between 63psi-70psi.

 

Alrighty...resurecting this, lately i noticed that the fuel psi gauge was reaching 80+psi. Messing with it, i noticed if i moved the wires for my trailer brakes, it would make the gauge fluctuate around. Given that, i quit screw'n with it and let it play its part. The gauge hovered quite persistant at 80-ish psi. So, i removed the FPR, wet-sanded the plunger and re-installed. To my surprise, it didnt do anything. So, a few days ago, i re-removed the FPR, and this time, cut 1 coil from the spring..(did this about a year ago, to the extent with using the FRx FPR housing, had to install a B.B. to bring psi back up), with cutting 1-coil, the gauge now is a steady 69psi. Here's the kicker though, the "drop" in rpms have deminished now, when bring'n to a stop/downshifting/throwing in N...

My "hypothesis" conclusion to this, is that i was seeing WAY more psi then my injectors liked and could not burn the excess fuel. Also like to point out, while with the higher psi, at WOT, i'd get a cloud of black smoke, from 3rd gear on. Also, when motor was warm, start ups took an easy 4-6sec to fire off. Now, with the new psi readings, no more drop in rpms along with no black smoke AND start ups when motor is warm, are NO MORE than 1 sec.

 

The closer to 65 psi your fuel pressure is, the more horsepower and mpg you will see. I can't speak to the specific symptoms you speak of, but I know that 80 psi is too high. It may be time to install a fuel pressure gauge in the cab. That's the only way you will know for sure if your fuel pump is keeping up.

Drake