Checking Fuel Pressure (Vehicles Without Fuel Rail Test Port)

Relieve fuel pressure. On vehicles with vacuum assisted fuel pressure regulators, disconnect vacuum hose from fuel pressure regulator before checking fuel pressure.
On all vehicles, disconnect fuel supply hose from chassis lines at engine. Connect Fuel Pressure Gauge (C-4799) to appropriate fuel pressure test adapter. Install adapter between fuel supply hose and chassis fuel line.
CAUTION: DO NOT activate fuel pump for long periods, or engine may hydrostatically (liquid) lock.
Turn ignition switch to ON position. Using Diagnostic Readout Box (DRB), select ASD FUEL SYSTEM TEST mode. In this mode, DRB energizes Auto Shutdown (ASD) relay, causing fuel pump to activate and pressurize fuel system.
Note fuel pressure, and record reading. Stop ASD FUEL SYSTEM test mode. Relieve fuel pressure. Remove fuel pressure gauge. If fuel pressure is within specification, fuel system is functioning properly and further testing is not required. See FUEL SYSTEM PRESSURE SPECIFICATIONS table.
If fuel pressure is greater than specification, go to step 8). If fuel pressure is less than specification, install Fuel Pressure Gauge(C-4799) and fuel pressure test adapter in fuel supply line between fuel tank and fuel filter.
Repeat ASD FUEL SYSTEM TEST. If fuel pressure is at least 5 psi greater than fuel pressure recorded in step 4), replace fuel filter. If no change is observed, gently squeeze fuel return hose.
If fuel pressure increases while squeezing fuel return hose, replace fuel pressure regulator. If fuel pressure does not change while squeezing fuel return hose, problem may either be a plugged fuel inlet strainer or defective fuel pump. Repair as necessary.
Disconnect fuel return hose from fuel pump at fuel tank. Connect appropriate fuel pressure test adapter to fuel return hose. Place other end of adapter into an approved 2 gallon gasoline container.
Turn ignition switch to ON position. Repeat ASD FUEL SYSTEM TEST. If pressure is now correct, replace fuel pump assembly. See FUEL SYSTEM PRESSURE SPECIFICATIONS table. If pressure is still greater than specification, deactivate fuel pump. Remove fuel pressure test adapter, and connect fuel pump return hose.
Disconnect fuel return hose from chassis fuel lines at engine. Connect fuel pressure test connector adapter to fuel return hose. Place other end of hose in an approved gasoline container. Repeat ASD FUEL SYSTEM TEST.
If pressure is now correct, check for restricted fuel return line. If no change is observed, replace fuel pressure regulator.