What was found
DURING A FUEL INJECTION SYSTEM CHECK WITH PRESSURE GAUGES IT WAS NOTED THAT FUEL WAS LEAKING FROM A VENT ON THE BACK SIDE OF THE ENGINE DRIVEN FUEL PUMP JUST BELOW THE LOW PRESSURE RELIEF VALVE ADJUSTMENT SCREW (THIS ADJUSTS THE LOW UNMETERED FUEL PRESSURE). THE LEAKAGE ONLY OCCURRED WHEN THE FUEL SYSTEM WAS PRESSURIZED AND WOULD NOT BE NOTICED ON A PREFLIGHT INSPECTION. THE LEAKAGE WAS STRONG ENOUGH TO SPRAY UP AGAINST THE FIREWALL. THE FUEL SYSTEM WAS LAST PRESSURE CHECKED DURING THE LAST 100HR, 80.5HR PRIOR TO THIS INCIDENT.