Over the past few weeks I’ve noticed the occasional hiccup under load or higher up in the RPM range but I’ve always passed it off as a speed bump or my imagination.

Today on the other hand was not my imagination at all.

What you are about to read makes me look like a total idiot, but the truck will give up driving home before I will.

I took on 31 gallons of fuel before heading to work. I drove 37 miles to work on a curvy hilly scenic sort of road and noticed on the last “big hill” that my truck was having major issues over 2000RPM or 15# boost.

I got to the location and decided to go ahead and pick up all the signs for the event I was working. I drove 20 more miles on the same hilly roads. The final leg of sign collection is flat and fairly straight. The truck began having problems getting above 1700RPM and 12# boost.

Initially, it wouldn’t free rev over 2200RPM, the engine just wouldn’t spin any faster. At the point where it was having problems over 1700RPM it was missing and would sometimes spin up to 2200 but usually was missing bad enough to keep it around 1800.

I was an idiot and drained the fuel filter housing in the parking lot without having any tools around. It took me roughly 10 minutes of bumping the starter, letting the LP (my 6th on this truck in 3 years) pump fuel in and then cranking it to see if it would fire. It hit once or twice and about the third cycle of bumping and cranking it started but had an awful idle.

10 minutes of running yielded a reasonably smooth idle. I figured it probably still had air in the lines but it seemed to be running worst when the grid heaters cycled on (which I don’t think they should at nearly 50 ambient on a truck that is still nearly at operating temp)

Anything over about 25% throttle caused heavy missing.

The drive home was the most miserable experience of my entire vehicle owning life. The only way I could get it up to speed was to give it maybe 10% throttle and wait (beg) for it to switch into 4th and lock the TC at 42 so I could get above 50. Hills were a nightmare. If the truck down shifted on the hill it was game over and a 10MPH hill climb was the end result. I had to give it enough throttle so it wouldn’t loose speed but not too much to start it missing which would end up losing speed and thus causing a downshift.

By the time I got back into town the truck wouldn’t go over 1400RPM or 5# boost.

When I turned into my neighborhood I couldn’t go over 1200RPM or ~2# boost without very heavy missing.

The truck stalled while making the second to last turn before my house but the truck fired back up without issue and made it up the second to last hill barely above idle. I thought the truck missed heavily at the top but I’d actually just hit a deer that came out of no where and couldn’t get out of the way of what sounded like a diesel jackhammer crawling through my neighborhood at 3mph.

Idle in 4WL conquered the final hill before my driveway.

10 minutes later I had to move my truck to let my roommate out and it started fine and would free rev to 3000 without a problem. My roommate, who heard me coming up the hill with my Cummins jackhammer and I had a laugh…

Truck history:
Factory LP as far as I know
6 lift pumps in roughly 3 years (I’ve gotten pretty efficient at it)
Stainless fuel lines from that company in Canada that used to post on this website whose name I can’t remember
No chip, no power adders
Oil changed regularly with fleetguard filters

Fuel filter is a little (ok a lot) over due (I think its been 14 months) but I cant imagine it causing this big of a problem… To take this even more out of the picture, when I got frustrated and floored it through the stuttering, white smoke poured from the exhaust leading me to believe it had plenty of fuel.

Please ye masters of the 24v, give me what advice you can.

I’m changing the fuel filter first thing in the morning.

 

up until your last statement I would have bet on a fuel filter, but that 10min wait then ran fine, made me think of a bad fuel cap, I've seen a 6.5 chev diesel collapse the tank until it would only hold 1/2 of its orginal capacity... or it could be a filter or a LP or a VP your pick

 

Hmm interesting...

I've never had an LP cause my truck to run funny and ive gone through my fair share...

The filter I know needs to be replaced but I have my doubts on that being the problem.

The fuel cap on the other hand is an interesting idea though. I remember being told that the fuel tank is vented and should not hold any pressure or vacuum. I now remember that as of about a year ago, my tank started holding vacuum and would suck in a rush of air when I took off the fuel cap.

 

It does sound like the engine is starving for fuel, some diesels when the filter plugs, can't draw enough fuel so the engine slowly looses power.
I just read your post again and from what I've read about the 5.9 white smoke is one of two things coolant or a bad VP (white smoke is unburnt fuel, likely the VP injecting it at the wrong time).
You should have the truck scanned for codes, if the problem is still there after doing a filter

 

Yeah its not coolant smoke, it's absolutely unburnt fuel smoke which is why I was thinking that a fuel filter wont save me.

Unless of course its not getting enough fuel to light off and that unburnt fuel had built up enough to dump a little smoke when I gave it full throttle

 

Update:

Started it before I changed the filter and it seemed to run fine.

The filter was uber nasty and weighed like 5 pounds. The canister had a quarter inch of what looked like fine brown sand around the bottom… It was pretty sweet.

Anyway, I got it fired up and it seems to be running like normal. It might just be my imagination but it seems down on power between 1400RPM and about 1700RPM but pulls like normal from 1800 to 3000.

*shrug*

I’m still not convinced that my fuel filter was to blame but at least now I’m fully armed with other possible tests and solutions that I can try should this problem ever return.

Thanks for the help.