Engine/Transmission (1994 - 1998) fuel consumption whoes....

[MMcCallie]

My last 2 tanks yielded only 6 mpg. Most of my driving is under 40 mph, short trips, and in 4 wheel drive high and low range through snow as deep as 4'. Not a whole lot of idling though. Never thought my mileage would get this low. My neighbor told me his 7. 3 PSD in Skagway gets only 4 mpg so maybe I'm not doing that bad? Does anyone else ever get down to the single digits in miles per gallon? Maybe its because my engine temperature is too low.

 

[LVJUNIOR]

my mileage sucks but I have never gotten that bad even crawling throught the mountains at -20 on a hunting trip

 

[CNunamaker]

Dont mean to step on your post but I am having a similar Problem with my 98 24 v truck I am only getting 9. 6 MPG. I only have 133000 miles on it it is bone stock I bought it 3 mths ago and had my local Diesel Mech. Scan it and do a runability test on it and he said that it ran great New fuel and Air filter. The straing thing is that getting only 9. 6 mpg's it doesent smoke like its eating the fuel????? had dodge re flash the memory to most current settings, Mech. is boggled as well. HELP

 

[wcjp]

Have you guys checked the brakes? Dragging brakes would cause all of the listed problems. Try using an infrared thermometer. When towing with my 06' with my slidein camper, jeep and trailer my brakes are 99deg after immediately stopping. I do use an exhaust brake. Look for one or two wheels to be way different.



On my 96' I also had to replace the D80 internals. They caused an immediate mpg problem.

 

[The patriot]

Ever since I went to the UTE bumper my mileage has dropped.

Since it seems to be more than an isolated case, can it be something like fuel reformulation?

 

[SRath]

You bet! That ULSD we are all paying so much for is not good fuel in any sense. Our semis at work all get crappy mileage now and have fuel system problems. I'm sure the Big Oil execs and OPECkers love it (follow the money)! The new smog crap makes it even worse and is a maintenance nightmare. A little bit less pollution per gallon maybe, but many more gallons per ton per mile equates to more pollution (and oil sales) overall. Gotta love the enviro-whackos and bureaucrats!

Throw in the cold weather and blended fuel, and you will definitely see lower mpg. But the numbers some of you guys are talking is worse than a well-built 454 chevy gasser would get. That really stinks!

 

[The patriot]

Is there an additive that can remedy this?

 

[fest3er]

Is there an additive that can remedy this?

Try a double dose of almost any commercially available cetane boost; Stanadyne and Amsoil are good, and there may be others. If the problem is low cetane, you'll see a difference immediately. If you see no difference, the problem won't be the fuel. If you do see a difference, drop to a single dose the next tank and check the fuel economy.



With mileage slowly getting worse, it could be a seasonal change in fuel, it could be a decrease in fuel supply pressure (which *can* affect the p-pump), it could be a gradual change in injector pop-off pressure.



If your engine was well tuned before, you should've seen a greyish haze under full fueling. If that has changed to darker grey or even black (and you have more black around your tail pipe) it could be atomization has gotten poor and the fuel isn't burning as well as it should.



If you aren't sure about the fuel quality, check into the lubricity. Down around Houston, at the time of the changeover to ULSD, there were a lot of pump failures due to horribly insufficient lubricity. This is a remote possibility.



Is the fan clutch 'released' or 'seized'? IF it doesn't release, the fan'll suck down extry fuel (but not 100% more).



Do you know someone with a good working 12V? If so, put a stethoscope on the injectors and other parts and listen; get a feel for what things should sound like. Then listen to yours. If injectors, delivery valves or other things aren't working right, you should hear the difference about as fast as you can snap your fingers.

 

[JMalik]

The OEM fuel heater on the Lift pump overheats its connector contacts and develops small air leaks through the connector. I experienced this on my lift pump. I removed the fuel heater and used a Mityvac vacum pump to test the connector to find the leak. Then I took the heater a part and found the heater/connector spring contact was burned. The burned contact had melted the housing plastic around the connector contact producing the connector air leak.



Another test is to just remove the lift pump fuel heater and re-install the fuel bowl/screen Then run your truck without the heater and check your milage. I am now runing my 96 without the fuel lift pump heater.



If your pump is an OEM pump it may be coming apart. My 96 had an AC pump manufactured in England. On testing it I found it also had air leaks along with a broken check valve spring. The pump still worked and my engine performance/milage unloaded still ranged 17 to 19 mpg and loaded 12mpg. This pump produced 25 to 30psi. The new pump, from Genos Garage, produced 27 to 32psi without the fuel heater. The fuel pump tests were curb side tests without loading the engine.

 

[JMalik]

Forgot to mention the only symptom of a problem was the engine was slow to start. Rather than starting on the first crank after sitting around for a day or so it took several cranks to get it started. The bad lift pump check valve was leaking.

 

[fest3er]

Other things to check:

• Is the boost line from the manifold to the AFC intact? And is the AFC properly adjusted?
• Remove the oil filler cap and tie some decent cloth over it (keep the dust out). Maybe excess crankcase pressure is causing a problem...
• Check your fuel pressure (again?).
• Pull two or three injectors and visually inspect them.
• Make sure the turbo spins freely hot or cold.
• Make sure valves are properly adjusted.
• If it has EGR, is it working?
• Is the wastegate working properly?
• Are any brakes dragging? Wheel bearings getting tight?
• Did an earthquake change your once-level road into an 8% grade? Is it now uphill to all your destinations?