CM2250 Poor fuel mileage

[Rawze]

There are a thousand + factors that contribute to fuel mileage problems.

If it were carbon packing causing it, then someone with experience could feel it when they turn the engine by hand.

An issue like that could be anything.. including the fact that maybe you have more average power or are driving it differently, etc. than other people.. and the truck and rear end specs make a huge difference too.

Could even be the head worn out and loosing compression.

Can also be a lot of non engine related factors .. even a bleeding Doser injector or fuel line somewhere dripping. .. or maybe even you filling the tanks to the very brim and it bleeds the fuel back out the bleeder-tubes as it warms up later. This is ion fact a big problem with drivers when they fuel. They try to put every drop of fuel into the tanks that they can.. and 10+ gallons sometimes.. bleeds back out as the truck sees its first hill, or as the fuel heats up and expands. -== NEVER EVER TOP IT OFF!.

When you fuel the truck... shove that pump nozzle as deep into the tank as you can.... when it 'Clicks' off on its own ... .. DON'T RE-START IT. -= IT IS DONE!. Adding more fuel is only going to end up on the highway somewhere as that tank and fuel heats up.

I know that certain model pete's and KW's are notorious fort developing a fuel leak right in a cross-member on the return lines.. and then drip fuel right down onto the damn driveshaft itself. -=-= Takes an expert eye to even see this, as there is almost zero evidence of this happening, and most truck owners will never find an issue like this on their own.. all wondering why their fuel mileage is total s#it.


HAVE YOU pressurized the fuel tanks with up to a max of 10-psi and let the truck sit for a few hours?.

-- You can pressurize the fuel tanks to 10 PSI by pinching off the bleeder tube on one fuel tank, and putting a bit of shop air on the other tank, to check for leaks or if air is getting into the fuel as a last resort.
WARNING::: - DO NOT ATTEMPT TO REMOVE THE FUEL FILL CAP WITH THE FUEL TANKS PRESSURIZED!, not even if there is only a few psi!.. That cap can hurt a person badly or break bones if it blows off there with only 10 psi of pressure on its backside!.


Pressurizing the whole engine will find a lot of fuel mileage issues.. and checking the head for compression losses.. and there are a whole host of things that can be checked.

Does the fuel mileage in the ECM match, fairly closely to what you can calculate to the pump on a receipt?. -=-- I.E.> does the ecm know where the extra fuel is going and is accounting for it?.