trying to find fuel milage problem. 7mpg light towing 10-12mpg empty and easy. i really do drive like a granny. installed fuel pres. and boost gauges. boost in normal cruising 55mph reads 1-2. wot reads 17 max
bone stock 98.5 24v 3500 75k mi. auto 3.55s . fuel pres. good. new air filter.

 

What type of fuel pressure are you getting? There are lots of things that can affect fuel mileage.



Luke

 

new fuel filter??? that alone will drop your mileage. also, check your tranny fluid, make sure your tires are fully inflated, basicly check the basic maintance stuff. 17 psi at WOt, stock, i dont think thats too bad, but only 12 mpg, is that highway??? how much city driving do you do???

i know i can get 20lpus mpg highway and 15 city with my setup making over 450 hp and even on my stock 98, i see 16 average

 

Something is bad wrong!
I'd try changing the AIT sensor,if you are going to throw parts at it,did you peel the sticker off the air filter?
I've NEVER gotten as bad as 7mpg out of mine,I got 9mpg once hauling a 38'toyhauler.

 

11 psi idle 6-7 wot new fuel filter

 

the other question is, try reseting your APPS sensor, that can affect it as well

 

how do you reset ?

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ait clean and ohm. tests ok meets cummins readings

 

bad injector?

 

how much black smoke are you putting out. more than normal? also, are you sure it is the enginesfault for the low fuel milage. you might have a fuel leak somewhere

 

ill talk to my friend that works at cummins test cell and see if he can provide anylight