Engine/Transmission (1994 - 1998) Really poor MPG

[Ghost Rider]

I'm really getting bad mileage. I know winter fuel gives bad MPG, but it was bad in summer too. About 16mpg last summer, today 10mpg. This is horrible for any time of year. I drive average most of the time, but I do stomp it from time to time, Can someone give me some advice on where my problem might be?

Note: Until 2 weeks ago, I was running 33's, now I have 35's.

 

[SBashaw]

Have you had your speedo recalibrated for the larger tires?

 

[Ghost Rider]

Well, no. I wouldn't have thought it would make that big a difference.

 

[CTD12V]

Definitely will make a difference. On my truck, just changing from the stock 245/75s to 235/85s made me read 5 miles low every 100 miles. So your odo and speedo functions are very likely reading low. The larger tires are probably also taking a little more fuel to get moving when you are accelerating.

 

[RDHamill]

I'd think it would be worth it to have the timing and injectors checked, along with the turbo and air intake.

OR you could try my 6. 7L, then you'll be happy with what you have.

Sorry, had to say it.

 

[Vaughn MacKenzie]

Ghost Rider have you done any basics like check your fuel pressure, service your prefilter, make sure the fuel heater isn't leaking or changed your fuel filter lately? Also have you ever checked to see if you have any boost leaks. . . do you tighten you clamps a couple times a year?

Also do you get much smoke at startup, does it stink or haze? Still have the stock injectors?

Is your 10mpg mostly city driving or cruising up I-24?

I see you're in Clarksville, we have a guy at my job here from Clarksville for a few weeks, returning next month. I think he said he lives in Briarwood (?)

 

[Ghost Rider]

Haven't checked pressure, prefilter?, fuel heater, i have changed fuel filter lately. What's a easy way to check for the boost leaks, and no I don't tighten boots routinely. Stock injectors, and city driving, not lots of heavy traffic though.

 

[BPowers]

Get a direct pressure reading gauge to see if you are losing any pressure. This way you can drive around and check it out

 

[Vaughn MacKenzie]

Haven't checked pressure, prefilter?, fuel heater, i have changed fuel filter lately. What's a easy way to check for the boost leaks, and no I don't tighten boots routinely. Stock injectors, and city driving, not lots of heavy traffic though.

• Prefilter: There's a little bowl-looking thing by the lift pump. Remove w/17mm socket and clean sediment out, but before doing that buy the service kit to have on hand (about $8 from Cummins). Read more here: Fuel Pre-Filter Cleaning on Ram/Cummins
• Heater: When you have the prefilter off, unplug the heater then take an allen wrench and remove the bolt holding the heater puck in place (it's a flat disk thing). Inspect electrical contacts, clean it up good, then try blowing on the electrical connector with your mouth. . . if it leaks air throw it away. You don't need to have the heater, go ahead & put the bowl back on without it, or you can run that way until you buy a new one.
• Boost leaks: Just make a close inspection of your boots. The first one where the turbo feeds the intercooler often gets cut on the inner fender. Take a 5/16" deep socket and snug them all down. . . don't reef on them, don't need to go real tight.
• To check fuel pressure you'll need to come up with a banjo bolt with a schrader valve, I used one off my 2001. . . replace the outlet side banjo bolt atop your fuel filter (toward front of engine) then you'll need a pressure gauge like they use for testing fuel injection pressure on gassers. Pressure should be a good 12-15 at idle I think & 25+ at higher RPM (someone help me on those numbers though).


Vaughn

 

[vaicase]

blame it on big oil. they are using a way to make fuel so they get more profit and the truck will still run get worse mileage. they make more money. we lose. just like gasoline. i mean look at ethonal. it will mess your engine up. if you dont believe me. take a little diesel out,and look and smell. is not nothing like it was a couple of years ago. remember the guy from kansas said this. ive been around diesel trucks since my army days in the 70'sthanks

 

[Ahopper]

not meaning to steal the thread but i didnt want to make another one for the same problem. yesterday i filled my truck up to the neck of the fill tube installed a bhaf and drove to mexico. i was pulling maby 1500lbs. i have gotten 21 mpg with the same setup going the same distance. i had the cruse set at 66mph. the only thing i have changes is put a shell on with a roof rack but i dont think it should contribute to a 6mpg decrease in milage. someone help me out.



p. s. diesel is $2. 25 a gallon down here. i just paid 3. 84 in the states. i dont understand it!#@$%!

 

[JPittinger]

At least check all your rubber boots to make sure none of them have slipped out from under the clamps. I've lost 5 mpg from this before. -JJ