Jerry Stewart from AVI explains a formula to calculate gallons per minute (GPM) from engine horsepower.

Formula: (Horsepower * 0.5) / 6 / 60 = GPM

Example: A 350 HP motor:

(350 * 0.5) = 175

175 / 6 (fuel weight) = 29.16 gallons per hour (GPH)

29.16 / 60 = 0.49 GPM

This formula, combined with a volume tester, allows for accurate fuel volume determination. Stewart gives an example of a Ford Focus that surged at high speeds (120-140 mph). Instead of dangerous road tests, he used a volume tester in the bay, which revealed the fuel pump’s volume fluctuated when warm, making diagnosis easy.