An engine that "coughs" or hesitates is starving for either air or fuel. We diagnose common causes, including clogged water separators, failing lift pumps, and blocked DPF filters.

If your tractor sputters specifically when pulling a heavy load up a hill, the primary suspect is fuel delivery. A weak electrical transfer pump (lift pump) may provide enough volume for idling, but it fails to keep the high-pressure injection pump primed under maximum demand. Another common culprit is a collapsing inner liner on an aging rubber fuel line; the suction from the pump pulls the soft rubber shut, restricting flow. Mechanics use clear sight-glasses installed inline to check for air bubbles being sucked into the system, a condition that will make any diesel run terribly.