Engine/Transmission (1994 - 1998) fuel milage

[ALehman]

I have a 94 dodge 2500 4X4 auto. when i purchased the truck in march of 03 it had 75,900 miles and i got 17. 5 mpg. now i have about 93,500 straight 3'' pipe and 315x75xr16 tires and fuel turned up 20% and valves adjusted. my fuel milage has dropped from 150 miles to a 1/4 tank to 100 or less to 1/4 tank. whats the deal. i know the cold does it a little but that much. i was still getting 150 when i put the tires on but not now. i even changed my air and fuel filter but no change

 

[DSiemens]

Welcome to the site. Don't know if you are experiencing winter at your location, but if you are then the mileage decreases. There are lots of good posts here and great people. Welcome.



Dan

 

[DRAG DIESEL]

don't go by your fuel gauge... . go by how many gallons it takes to fillup from empty...



The fuel sending units are inharently bad... if it's doing what mine was doing, it's on its way out.



Best of luck.



~DD

 

[krs]

Hi there!



What do you mean by "fuel turned up 20%"?

Your engine doesn't have adjustments for "turning up" the fuel, really, without making internal changes to the injection pump.



Also, you said that your milage stayed good after you put on your new tires but are you sure of that? Bigger tires change drive ratios. The ones you have will make a difference of about 10% and it means that when you figure your milage you should add 10% more miles than your odometer tells you.

Then when you divide miles by gallons you'll get a bigger result.

 

[ALehman]

what i meant by turned up 20% is that i had my pump adjusted with the adjustment screws on the pump. also i am experiencing winter, williamsport, pa where we have been in the 20 degrees and lower.

 

[mainer]

Also, I believe that your fuel efficiency is reduced with "winter mixed" fuel. Add that factor, with colder air that's harder to push, and with the 10% odometer error caused by your tires and there's the reason. Hey, as long as the heater works... .

 

[krs]

ALehman,



"what i meant by turned up 20% is that i had my pump adjusted with the adjustment screws on the pump"



Not to belabor the point, and I don't mean to be critical of you or your experiences, but if someone charged you money to do this" "turn up" they may have ripped you off. It's that the phrase has a wrong ring to it for a 1994 truck.



The earlier diesel Dodge trucks, from 1989 thru 1993 do have adjustment screws on their injection pump and can be turned up somewhat and that's probaly where your mechanic learned to say such a thing, but there are no power adjustment screws on your 1994 -1998 P7100 injection pump, per se. While it is possible to realize some improvement by relocating certain parts of the pump (sliding the AFC housing/camplate forward) it's not a part of the usual mechanic's bag of tricks to do that. It is , unfortunately, a big part of the usual mechanic's bag of tricks to say that they've done some unverifiable thing, doing absolutely nothing, and charging some amount of money for doing it.



It's water under the bridge now and you've come to the right place. I think that it's safe to say that no member of this site will deliberately steer you wrong.



ps ed: by the way, the pump you have is MUCH more modifiable than the earlier one and you can use it to make so much HP that you'd barely be able to drive the truck (!) - just not by adjusting screws. Here's a good place to get a short course in power and the differences between the Dodge diesel models:

http://www.tstproducts.com/

 

[ALehman]

Let me explain what i mean by "turned up. " I mean that my fuel pressure was turned up. There are adjustents for fuel pressure.

As far as my mechanic he is one of the best pump guys i have ever seen. If you would see his 96 cummins you would know why. I will just plug this in. If you live in southern pennsylvania, go to antrim diesel in greencastle pa. Thats anything from a N14 cummins and up or clear down to our 5. 9. Trust me, they know what they are doing.

 

[krs]

"There are adjustents for fuel pressure"



Hmm, maybe you could let the forum know about those?... ... . it could save some people the cost of new overflow valves.



In any case, changing the fuel pressure shouldn't effect your milage or your performance unless it was very low. Did your guy tell you about winter fuel? Without changes to your fueling rate that's got to be the reason for your lower milage figures.

 

[LeeNH]

Well, I know cold up here (New Hampshire)... it was below zero all last week, I can tell you that REALLY does kill the ol MPG!



Winter fuel has additives that help the cold weather pour factor, but hurt MPG.



Another factor is you probably let it idle longer each time you start it to warm it up (not much fuel used there, but it adds up)



You can gain a little MPG (at least I did) by putting cardboard between the intercooler and the radiator to keep it within a good temp. operating range.



The last thing that is directly related to MPG is your right foot. Like all the rest of use, after the truck is bombed... ... . well, you have to make sure you got more power out of it, so your foot is into more, thats the whole idea right?



PS, I just filled up tonight... . $1. 76 a GALLON!!! Ughhhh.



Lee

 

[JLehman]

NO COMMENT ON FUEL JUST LIKE UR NAME LOL

 

[JoshPeters]

My milage here in MN drops considerably when they start running winter fuel. I'm talking 18 or so in the summer and about 15 in the winter. I try not to let it idle to much due to cylinder washing concerns, but when it's -10(day time high expected next week) and you can't plug in... you gotta do what you gotta do.....



Josh

I really should talk work into putting in an outlet at my parking spot... .

 

[midwestdually]

letting the truck sit and idle/warm up is another big killer like previously mentioned.

 

[JLEONARD]

22 to 24 summer

Take off 2 for winter.

Sorry... . got an old efficient truck.

And it's got balls too!!!!

CTDs rule!!!

Jay

 

[dpuckett]

Rub it in, why dontcha? I challenge you to do that with the local crap they call diesel here. From CO to here, I drop a minimum of 2 mpg, regardless of weather. I'm up to about 18 now; basically ALL town driving. 4 mi gravel, 2mi balcktop to STOP sign, 3 more miles to work. Cold start, then reverse. SO I may top 20 on a hwy trip, just have to go somewhere. Timing does have a great effect on MPGs.



Daniel

 

[ALehman]

my buddy's got a 92 D250, stacks, different turbo. He gets about 24 but he says it's cause of the old rotary pump

who knows