At what level should the fuel tank be?

• A. 2/3
• B. Full
• C. 1/2
• D. 1/3

Answer: (A)

Maintaining a sufficient fuel reserve during pump operation is essential to prevent fuel starvation and ensure the engine can sustain the run and priming when the pump is in use. Keeping the fuel tank around two-thirds full provides a comfortable margin: there’s enough fuel for the duration of the test, the suction line stays primed because the pickup remains submerged, and you have a buffer if the run lasts longer or you need to re-prime. Filling beyond two-thirds isn’t necessary for the typical test and adds extra weight and potential spill risk, while going lower than two-thirds raises the chance of running the tank dry during higher engine loads or during priming. Therefore, two-thirds is the recommended level.