my cummins shoots up to 2500rpms then spit and spudders down to 2000 rpms and i let off and cruise, then step on it and it does it again. it stopped for a day, then i went to the store and it did it again? i cant even get up to high way speeds. idk why. any ideas?

 

It may be not getting enough fuel bud, i know my conversion cummins the airdog kicked off one day and it'd run good until you got to the top end and needed the fuel and it couldn't get enough?? just a thought. filter or lift pump

 

i dont know where the stock lift pump is in it. and ill put a new filter in it tomorrow

 

Stock lift pump is on the drivers side of the block below the fuel filter bud. You can check the pump when you screw the old filter off s little ways and have someone crank the motor and see if it push's any fuel out. poor boys way

 

someone said something about the fuel shut off soleniod acting up also?

 

Well i won't argue with you on that.... but i've never seen one that just half way goes out. if its opening up all the way then its right. but i've not seen everything. mine had a short one night and i had to wire it open but it killed the pick up dead like up turned the key off.

 

start the engine and reach under the injection pump towards the back and lift up on the shutoff solenoid. if it moves up at all then the magnet on the inside has went bad and will need to be replaced.

 

iv e heard of one not opening all the way and it making a turned up run like a stock one. so a stock one like a sick one maybe? just go out there after it cranks and push it and see if it will go any farther than the solenoid will push it