I put 3 gallons of fuel into both main tanks and backed the aircraft down the ramp leading up to the hangar. I jacked up the front of the aircraft and achieved 18.5 degrees of fuselage up angle. I assumed 25.3 gallons per hour of fuel requirement at full throttle and sea level. As discovered by Russ Erb, I was unable to achieve the AC 90-89A-required 150% of the fuel pump off both position fuel flow of 38 gallons per hour, and in fact only obtained 17.8 gph. With the fuel pump on and in the both position, I achieved 33.0 gph, which is greater than the AC 90-89A-required 125% value of 31.6 gph. I didn't recheck the fuel pump off Left and Right only fuel selector positions, as I would expect them to not meet the AC 90-89A requirement. With the fuel pump on, however, I was able to achieve 31.6 gph on the left and right only position.