Ok, I have a 2001 3500 24V diesel cummins 2wd. Not sure what other information about the truck you need and I hope I am posting in the right place.

Gradual loss of power over a period of 3 weeks or so. MPG dropping also. Yesterday my milage dropped down to 12/13 mpg.

Now I've heard/read that if it was the lift pump it should be blowing white smoke and have a rough start. It is currently 37F (degrees) and it started like a dream with no smoke (of any color) coming out of it. The lift pump has never been replaced (that we are aware of and does not visually look new. it does look old) and we are at 225,000 miles.

The only other thing that has happened to this truck was a superchip issue. While reprogramming for towing the superchip went into recover mode. While trying to get through that the programmer became stuck. Called Superchips, the guy said unplug it and then you can try to start it. It turned right over and started fine. The guy told me it "Should be in stock mode." didn't say it was just said it should be. I'm wondering if this could be the issue?

 

First things first is get a fuel psi gauge and see what your fuel pressures are.....there is a test port on the side of the injection pump should be no less than 5psi on it hard and that's exactly even pushing the lower limits. At a idle you should be around 8-10psi...

 

Pull and clean, or replace your IAT sensor also. This can rob power with false readings.

You will need a can of electrical parts cleaner to do it right, IIRC you can ruin it with carb.brake cleaner etc.

More serious: Auto trans? could be slipping and goin south....I hope its the IAT for your sake....

 

Also, check/replace fuel filter. I you have run it low recently you may have sucked up sediment, causing a clogged up filter.

 

Most likely your lift pump is done and your injection pump is pulling the fuel which can effect your power/mileage, check fuel pressure! I have 232k on mine and have been thru 6 lift pumps, they don't last long unless you spend the money on a quality pump such as airdog or fass which is my next purchase.

 

SIX,were is the ait sensor? on an 01.

 

it's on the block right below the number 6 injector, a deep socket will be needed, 1 1/8 i think

 

Where Johnh said, but mine is a 13/16" deep socket.

 

ive heard from alot of people, that when you start loosing power, and MPG its a good sign that your IP is going out or starting to go out....

 

http://dodgeram.org/tech/dsl/mt_2_fe...l_sys_comp.htm