I have a 98.5 Dually 3500 5spd. It has 165000 on it. I used to get 18 mpg now it has dropped to 9-11mpg. When going down the interstate it acts like i shut off all power and then it will come back on. The electrical things all stay on but the motor kills out. Sometimes for only a second, sometimes it take me down to 40 mph and comes back on. My buddies '02 is doing the same thing. I drained the fuel filter several times to see if it was water but I dont think it is. Any ideas would be appreciated.

 

you may have a clogged fuel filter,
or is the fuel gelling on you.
Inspect your fuel lines for small air holes in case she is sucking in air with the fuel, that would make it have poor milege.
Does it start easy?
Last,
WELCOME TO DTR!!!!!!!!!!!!!!!

 

If you have a 98.5, 24v, you might try the APPS reset here. If this helps, do a search on "APPS" and you'll get a lot of info on repair/replacement.

 

have the codes checked and could be vp-44 or L/P. Hope it isn't.

 

Havent checked any codes but nothing is just poping up. I should also add, when my friend and I are both driving our trucks, sometimes there is a noise that sounds like a noisy lifter and then it goes away. Could it be an injector? I will try the grounds and reseting the other tonight. The trouble is it may take a week before it happens again so it may take awhile to know if I have solved the problem. Thanks for the help and suggestions, Lin

 

I have a cummins parts store near and wonder if it would be worth it to get new injectors. Is there a better one to put in it than another? Its a 98.5 24Valve, thanks again, Lin

 

The symptoms you are explaining sound very much like a dying injection pump. Get the codes read! The lifter sound is part of the surging sound you're hearing from the dying pump. Sorry to be the bearer of bad news ... I'm in the same boat!

 

will a dying injection pump throw any codes without tripping the check engine light??

 

It is possible that a code may be stored withou the CEL. VP's are notorious for dying without throwing a code. Mine has tripped the CEL a few times. She will run for weeks without a CEL and still show the symptoms, then, out of the blue, I get the dead pedal or a stumble and the CEL is there for a couple of days. I noticed the surging sound long before I ever tripped the CEL.

 

I have noticed the dead pedal ever since I have owned it, 15,000 miles. Once in a great while. Bought a Superchips 3705 today and will see about the codes thing when it gets here. Will keep you informed. Thanks again, Lin

 

Found shavings in the fuel filter, not many but they look to be aluminum. Anything to be worried about?

 

Na, that's been there each time I've replaced mine. I've read posts where others are reporting the same.

 

I figured it could be coming from the gas stations pumps or something.

 

Probably from the lift pump these trucks have on them stock. The housing is die cast.