What would cause fuel pumps to run constantly when the key is turned on? You can hear them come on with key on and stay running full tilt entire time key is on. Car previously had a return style setup on it but I Have swapped pumps, check wiring on fpdm, back to stock lines, tune is basic email tune for pulley only. On the computer it shows fuel rail pressure at 74. Fuel pump voltage from table shows 15.00. Fuel pump duty cycle is at .50