Most people using a game pad are having this problem. I have the solution.
What you need to do is run as you normally would by holding forward on the joystick / mini stick and at the same time holding the left 'shift' button on your keyboard. The left shift when held on will bring your gun to your body (sprint mode) instead of running and pointing. When you get to the end of the ramp press the jump button once and let go of the sprint (left shift on keyboard).
I spent hours trying to to jump across before i realized that i needed to engage the sprint. This really does work. Good luck.