Engine/Transmission (1994 - 1998) Change in fuel economy

[McLaughlin]

In the last four or five weeks, my fuel economy has dropped from 17+ to around 12 mpg (last tank of fuel). I've also noticed white smoke on start up which seems continuous. The smoke isn't real noticeable unless you are following the truck and seems more like a grayish haze then anything else. I haven't noticed it after a couple of miles or so but noticed the truck them seems to produce black smoke some on light acceleration when pulling away from a stop light. Before the mileage drop, I only noticed some white smoke when first starting the truck.



I'm wondering if I got a tank of bad fuel or if I could have introduced an air leak when I installed my boost gauge. I did a quick check for obvious air leaks but didn't notice anything that seemed wrong.



I'm thinking that I should change out the fuel filter and put in some diesel additive/injector cleaner. The fuel filter air filters were changed about 1300 mi ago.



I would appreciate any suggestions regarding what to try to figure out why my mileage dropped off so quickly.



Nearly forgot. I have a stock fuel plate, a DTT transmission with about 1100 mi on it, 4 in exhaust, and 3K gov springs and a BHAF. The check engine light is not on and I haven't tried to pull any codes.

 

[Cooker]

If you picked up a bad tank of fuel your fuel filter could be plugged. To start I would fill up with fresh fuel and change your fuel filter. A plugged fuel filter will decrease fuel pressure which will have a negative impact on fuel economy.

 

[Centeno1]

hmmm

check your turbo make sure its spooling well and hasn't warped check the housings for rub marks at intake and exhaust.



had a turbo bgo bad on me cause i shut it doen too hot and within 2 days i was down to 10 mpg from 18... ... . ouch

 

[bmoeller]

If the filters don't fix it, check the fuel pressure. Could have a bad overflow valve.



http://dodgeram.org/tech/dsl/troubleshooting/injector_pump.htm#Overflow



Also have the pump timing checked next. Sometimes the timing will slip.



http://dodgeram.info/tsb/1994/18-10-94a.htm

 

[Cooker]

I didn't suggest a bad OF valve because it is not likely that it failed all of a sudden. The decrease in FP resulting in lower MPG's is a bit more gradual with a failing OF valve than what the original posted suggested. Nonetheless, I would agree checking the FP may be a good place to start also.

 

[dodge cummins]

white smoke especially when truck is warm is usually a timing issue.

 

[McLaughlin]

Thanks for the suggestions. Unfortunately, my troubleshooting suffered a setback when some yahoo decided to make a right turn from the left lane in front of my wife.



Truck came through in pretty good shape, driver side front bumper pushed back about 6 in, driver side fender abit crumpled, grille broken, alignment hosed and some other minor damage. The other car was a rental and passanger rear corner panel was moved about 3 ft closer to the back seat and the front bumper moved back about 6 in from impacting the car ahead. Wife said she saw it comming in slow motion but could avoid it. Also, said that she wasn't jolted around much at all. Wasn't even sore afterwards. People in car that caused it, and were ticketed, were OK also but the guy in the front car broke something or another (don't know what).



So right now, I'm trying to get the damage fixed and am not driving the truck anymore then I can avoid.