Fuel Pressure Test

NOTE: Check fuel system pressure only when fuel cylinders are at least half full.

Remove engine cover. Remove air filter. Remove service port cap from fuel rail. Attach 0-300 psi pressure gauge to service port. Start engine and allow to reach operating temperature. Pressure should be 110-125 psi. Factors affecting pressure are:

Fuel Pressure Regulator
Engine Temperature
Ambient Temperature
Low Pressure Fuel Shut-Off Solenoid Condition
Fuel Injector Condition
High Pressure Fuel Shut-Off Solenoid Condition
Engine Load Requirements

If pressure is more than 125 psi with fuel cylinders more than half full and engine at operating temperature, replace fuel pressure regulator. If pressure is less than 110 psi, check; fuel level, all 4 fuel control valves are fully open, manual fuel shutoff valve is open and fuel lines for kinks or bends. See Figure . Check low pressure shutoff solenoid, high pressure shutoff solenoid and fuel injectors. See LOW PRESSURE SHUTOFF SOLENOID or HIGH PRESSURE SHUTOFF SOLENOID under MOTORS, RELAYS & SOLENOIDS and FUEL INJECTORS under FUEL SYSTEMS in SYSTEM & COMPONENT TESTING - RAM VAN - CNG article. After test is complete, remove test gauge. Install service port cap and check system for leaks. See LEAK CHECK . Install air filter and engine cover.