Ok we have an trivia oddity for folks.
The last two winter road trips we’ve driven west from Denver through Utah to get to Southern Baja and this last trip, Nevada.

We get fuel at two major locations in Utah as we pass through. Which after this last trip, we think has caused a strange temporary effect to our running.

Our truck, no load no trailer, at high speed, 75-78 mph, maintains fuel pressure of 10-11psi consistently with no fluctuation, our RPM a steady 1800-2000. Yet you can hear very plainly with your ear the engine surging, as though revving up and backing off revving up and backing off. If you push down semi quickly on the accelerator you got heavy white smoke. Not quiet the same as low gear accelerating getting on a highway ramp.(3000 miles truck consumed not one drop of oil) Then when climbing a semi steep grade the power dwindled off though the peddle is pushed to the floor, and again still maintains the same steady FP and RPM’s. Then when we let off on the accelerator, drop back to 40 or 50 miles per hour, then suddenly it feels as if a blockage coughs through, and full easy power, at slight peddle, returns, for a while….This then repeated....

This holds for about 1-12 tanks of fuel, after Utah. Was only a suspicion. Then this last trip we only took on slighter amount fuel as only going to Las Vegas, Started to hear a bit of the revving not too heavy. Then on the return, Topped off a low tank soon as hit the truck stop (Cheaper than Vegas) and the serious effects started up like the November trip. We always fill in Beaver and Green River, (2 different brands major truck stops.) This time we skipped Green River held off to Grand Junction. Quickly started cleaning up, Added one more tank Denver and almost normal already!

We thought at first, November trip, it was all in our minds. Now with this last trip we know something’s weird, what that is, the fuel?, the truck?, us?, is the real question!!
Maybe they use a different winter additive and / or maybe if they do we might have a senor that’s not working up to par? All the while steady rpm’s, FP never below 10, and of course when back down below 40mph or idle holds about 15psi Also never lost fuel economy. Held still 19mpg average even with 500+ miles acting up.

Anyone else have similar effects? This truck has made this trekk over a dozen times and only this last 6 months this new gremlin appeared. Not like when we’ve lost fuel pumps or VP. Going to probable take into Cummins for a check up, Though seriously hate to spend the money when already again running so well. A catch 22.

2001 5 spd 190k
Current lift pump is at 80k miles
Current VP44 is at 70K

 

Over the past few months I have noticed the same thing at around 70 mph. Now I am in Palatka, Fl with my 5th wheel enjoying the warm weather, and it threw the dreaded 0216 code. I have had sporatic 0122 APPS codes but have been fixing it with the reset procedure. Now it seems I may have pump problems and have an appt. with the local dodge dealer tomorrow. I am a long way from home in VA. Luckily I have only 60k on my truck and it should be covered under warranty - the pump at least, I will probably go ahead and bite the bullet and replace the apps too. Long story short, you may be headed toward replacing the pump(s) again.