Thats the only way I can descibe this problem that has suddenly come up.
I am fluctuating approx 200 RPM when under load IE: going up an incline or accelerating with some heavy pedal pressure,Light crusing no problem,as soon as I demand a little more the Rpm's dip than come up,dip then come up at exactly 10 second intervals,seems like its starving for fuel. Fuel filter changed less than 2K mi.ago,no water in fuel light,I've no modifications to this truck, it has been ok since I bought it used last year (150,000 Miles). Could this be as simple as a fuel line sucking air? or could it be as serious as the injector pump beginning to fail?,I know this is a difficult thing to guess at,But before I start throwing tons of cash at it I thought I'd see if anyone else has had this problem and could offer some suggestions.I'm going to change the fuel filter again just to see but I have a sinking feeling its not that simple.
Thanks

 

what year of truck do you have (im assuming a 95)

my did the sorta same thing
it turned out to be the overflow valve

 

yes good guess, indeed a 95. I've read about the overflow valve and its failing to maintain pressure,That is the symtoms? I will try, that would be a cheap and easy fix. I'll let you know if it works. thanks for the input.

 

does it matter how much fuel in tank, this sounds like what my truck did when lift pump started going out. when tank was full it was fine anything under three-quarters it was sluggish.

 

no d-rod, currently tank is newly filled,just started happening,a few days ago at around half a tank,had a problem last year when I first bought it where it would die down and stall out,hard to restart,would go a mile or so and putter out again. that was the fuel filter,changed and no problem since. I changed the filter again about 6 weeks ago just to be sure I was good for the winter,this symtom is different.fades quickly about 200 rpm than comes right back,over and over again I counted about every 10 sec.as soon as I start a slight grade(as soon as the engine sees more than a light load). seems to take off from a standstill ok, shifts 1.2,3 than od,If I keep on it it starts with this little oddity,If I back off and cruise light throttle no problem,start up a grade enough to demand more input,even slight steady input and the cycling starts.If I try to get on it while on level ground same deal.does'nt matter if at 1800 rpm,2k,2250 it does it same at all rpm,fades about 200 like its gonna shutdown than come right back up,until I finally back off to light input.

 

Check the fuel pressure> http://www.cumminsforum.com/forum/94...-12-valve.html

If you don't want to do the gauge:
Service the prefilter> http://dodgeram.org/tech/dsl/filter/pre-filt_clean.htm

If that doesn't work:
Change the OF valve.
Best price> http://www.fostertruck.com/Overflow_valve.htm

If that doesn't work:
Change the lift pump.

 

Thanks,overflow valve and pre filter kit on the way,will post results asap.

 

Well I did the pre filter primary filter and overflow valve and still same issue, I guess its going to be a lift pump next. I suppose it cant hurt and is only 100 bucks. I'll post results

 

good luck!

 

Put on a new lift pump and so far so good,have not really had a chance to get out on the open road yet,but around the neighborhood all seems happy in cummins land,truck is much more peppy and I cant get the symptoms to repeat. not too bad of a job,got done just before the snow started here. was starting to go to work in the truck today,but work shutdown cause of the snow(north jersey got hammered some 20+). thanks for the advice.

 

Still no Good,Am getting a sump and all new lines.Mabey,Just Mabey.

 

man that blows keep posting.

 

Hellman Sump and New Fuel line on the way,should be here by Fri. Starting the work this weekend,took Monday the 10'th off Just in case.Don't want to leave it unfinished.

 

Sucess, previous owner was a hack. He removed the in tank filter and put a piece of 5/16 line with a 1/4 npt barbed fitting pushed into the end. That line was plugged up with what looked like clear plastic flakes,I'm amazed the truck was getting any fuel. Well sump is installed,no leaks.New 3/8 id line run for supply. Took a 10 mile romp and ,She's never in my time of ownership run better. I kept waiting for Her to bog down or stall,and,Nothing. Man am I relieved. Let this help many on their quest of low fuel delivery diagnostics.
Thanks again for all the great advice.
Jeff

 

You may need to drop the tank and flush it out or the problem will happen again.
Alternative to dropping the tank is if you have access to a small electric pump you can suck fuel from the tank, though a filter then back into the tank.
Leave it running for at least 12 hours.