OK, I just had a recent drop in MPG that is a bit annoying. Was getting 17-18 MPG unloaded and mixed driving. I am now getting 14-15 MPG. And forget about towing mileage.

Truck is in sig but a quick run down is 1997 2500 auto, 4x4, 3.55's, #10 plate (almost full forward), AFC full forward, star wheel turned a bit, 215s and a Dodgezilla turbo. 125,xxx miles. Truck seems to be running the same, which has been good.

In the last 6 months I changed out the overflow valve to try and stop a slight ticking noise. It was cheaper than the lift pump and was probably due to be changed anyway. Didn’t fix the tick.

In the last 3-4 weeks I put in a new lift pump, diesel rated fuel hose from the engine to the hard lines on the frame. I removed all the connections and braided line. It was definitely over due. While I was at it I cleaned up the pre-filter screen. It appeared to be in good shape so I did not change it out. I also pulled the injectors and soaked them in some cleaner to remove some of the build up they had on them.

This fixed the ticking noise I had but it also was the start of my poor fuel mileage. I might have a leak some where but I am not certain where. Is there anyway to have installed the lift pump wrong? Could it be leaking thereby causing my drop in mileage? And if so where is it leaking? I read it could be leaking down into the oil pan but upon checking the oil it doesn’t appear that is the case. Well from looking at the dipstick anyway.

I just swapped out the fuel filter yesterday so I'll need to run a tank of fuel through it to see what my mileage is like. I also do not have a fuel pressure gauge setup but that is something I plan to do in the next week or so. I also plan to pull the injectors to have them pop tested. They are used injectors but I have been running them for a while without any issues, or so I think.

Any thoughts on what might have caused this sudden drop in mileage? I am pretty sure the station I normally fill up at has been on winter fuel for a few months now. I am not sure if they recently switched to the new fuel or not. Something I'll check later today. This drop in MPG is frustrating as I daily drive this truck. Any help or thoughts would be greatly appreciated.

 

I can't tell you if the new pump is the cause of your problems (I doubt it is), but it sure sounds like your on the right track trying to figurre it out.

The fuel filter change should help, and it may well be that the fuel has been winterized recently or more. The place you get your fuel may not even know if it winterized or how much?

Hows the temps been recently in your area? Any prolonged idling for warm up?

Good luck trying to track it down. KD

 

Ive done a LP

there is no way it can go in wrong, its only one way that it is installed and thats it. Your fuel problems could be from a fuel leak as you say, Check the return and feed lines to the injection pump for one. You say you have gotten a new fuel filter. What about the prefilter? As ive said before if you have to ask, you aint done it. The fuel heater assembly has a filter, about 6 bucks from fleetgard direct. Thirdly to say, still bad problems? You might need a new OFV (over flow valve)> with a fuel pressure gauge its easy to test to see if your LP and OFV are bad.. YOu need to pinch the fuel return line to find out, get a gauge in and get back to us.. for now those are worth checkin, and if the OFV is stock, then it needs to be replaced..

Rick

 

kd460, no real long idle times to speak of. Most of the time its 5 minutes or less. The temps have been a bit cooler lately, 20s or so during the day and down to low teens to single digits at night. Which is fairly low for us. But the truck fires right up after a couple cycles of the grid heater and a touch of throttle.

TXDiesel007, I didnt think it could go in but one way, figured I would ask anyway. I cleaned the pre-filter when I replaced the lift pump. It looked to be in good shape other than being a bit dirty.

I'll see what I can do about getting a fuel pressure gauge on it. I have changed the overflow valve in the last 6 months or less. Guess it could have gone bad. I 'll also have to crawl under the truck and look for any leaks where the rubber fuel lines connect to the hard lines. Havent seen any drips but that doesnt necessarily mean its not leaking.