A gasoline fueled engine with a new fuel filter shut down due to what appears to be fuel starvation. After a short shut down period, the engine restarts only to shut down again after a short period of operation. What component should we check first?

• A. Fuel rail
• B. Fuel pressure regulator
• C. Fuel tank cap
• D. Fuel pump

Answer: (C)

Fuel delivery depends on the tank being able to vent air as fuel is drawn toward the engine. If the fuel tank cap is faulty and won’t vent, a vacuum can form inside the tank as fuel is pumped out. That vacuum reduces the pump’s ability to pull fuel, leading to a momentary starvation and the engine shutting down. After a short rest, the pressure equalizes and the engine can restart briefly, only to starve again as the vacuum builds anew.

That’s why the first thing to check is the fuel tank cap and its venting. test by loosening or removing the cap (or replacing it with a known-good cap) to see if the problem clears. If venting isn’t the issue, then proceed to inspect the fuel pump, fuel pressure regulator, and related fuel delivery components.