We have a 2001 3500 diesel, 5 speed. It runs fine until we take a trip over 100 miles at a time. After 100 miles, it will hesitate on acceleration, randomly. The lift pump was replaced and it runs better than ever but it still hestitates on long trips (it will hesitate wheter or not we are towing a horse trailer). Any suggestion? Thank you!

 

Is it a stock lift pump?How long has this been happening ?Did it just start doing it after you had work done on it ? Have you got a stock fuel cap or a locking one? when was the fuel filter last done?

 

It is not a stock lift pump. The "100 mile" hesitation has been going on for about a year, before that there was no "major" work done on it besides regular maintenance. It has a stock fuel cap and the fuel filter was replaced just before the lift pump. Also, the check engine light has not come on at all.

 

i would start by checking the fuel pressure at the IP ,as well make sure the fuel filter is seal properly as well as change the fuel cap,,this pretty much eliminates any making sure everything before the lift pump is working properly and cheap to do ,,then i would be checking for air in the lines in other words bleed the fuel system to the injectors..i don't know everything just trying to help with what i would check others might have a better idea...but i am thinking you are getting some kind of lack of feed of fuel over time due to backpressure in the fuel system or air ,,this is just a guess