B5.9G, B5.9LPG – Troubleshooting and Repair Manual – 005-047   Low Pressure Regulator

NOTE: The low pressure regulator on the B5.9LPG and B LPG Plus is located in the evaporator and is not serviceable.

With the ignition switch in the ON position (do not engage the starting motor), check for combustible gas with a gas detector, Part Number 3823984, from the rear cover vent hole. A soap solution may also be used.

If a leak is detected, replace the low-pressure regulator.

Check for fuel supply pressure to the inlet of the fuel control housing. Refer to Procedure 005-061.

Before removing any component, turn off the fuel supply at the vehicle main fuel shutoff valve.

Start the engine and allow it to run at idle until it dies.

WARNING  Fuel is flammable. Keep all cigarettes, flames, pilot lights, arcing equipment, and switches out of the work area and areas sharing ventilation to reduce the possibility of severe personal injury or death when working on the fuel system.

Remove the fuel supply line from the fuel control housing inlet.

Remove the four capscrews and rear fuel control housing cover.

Remove and discard the rear cover gasket.

Remove the low-pressure regulator.

Remove the two coverplate capscrews.

Remove the coverplate and low-pressure regulator.

Replace all o-rings.

Inspect the sealing surface for nicks or damage.

The low-pressure regulator o-rings and the rear cover gasket must be discarded and replaced with new o-rings and a gasket.

Apply a light coat of Lubriplate™, Part Number 3163086, on the low-pressure regulator o-rings.

NOTE: The B5.9G low-pressure regulator is green in color. The B Gas Plus low-pressure regulator is blue in color.

Install the low-pressure regulator and rear cover (with new gasket) using four capscrews.

The low-pressure regulator o-rings must be discarded and replaced with new o-rings.

Apply a light coat of Lubriplate™, Part Number 3163086, on the low-pressure regulator o-rings.

NOTE: The B5.9G low-pressure regulator is green in color. The B Gas Plus low-pressure regulator is blue in color.

Install the low-pressure regulator and coverplate.

Install the two coverplate capscrews.

WARNING  Fuel is flammable. Keep all cigarettes, flames, pilot lights, arcing equipment, and switches out of the work area and areas sharing ventilation to reduce the possibility of severe personal injury or death when working on the fuel system.

Install the fuel supply line to the rear cover fuel inlet.

Turn on the vehicle main fuel shutoff valve.

Use a gas detector, Part Number 3823984, or soap solution to check all fittings for leaks.

If leaks are found, close the vehicle main fuel shutoff valve, turn the key to the OFF position, and repair leaks immediately.

WARNING  Fuel is flammable. Keep all cigarettes, flames, pilot lights, arcing equipment, and switches out of the work area and areas sharing ventilation to reduce the possibility of severe personal injury or death when working on the fuel system.

WARNING  To reduce the possibility of severe personal injury or death when working on the fuel system, turn off the fuel supply at the vehicle main fuel shutoff valve before removing any component.

Before removing any component, turn off the fuel supply at the vehicle main fuel shutoff valve.

Start the engine and allow it to run at idle until it dies.

Remove one elbow fitting from the jumper hose. Drill and tap the fitting for a Compuchek® pressure fitting. Clean debris from the fitting.

Install the elbow.

Connect a pressure gauge with a 0- to 689-kPa [0- to 100-psi] range to the elbow pressure fitting.

WARNING  Fuel is flammable. Keep all cigarettes, flames, pilot lights, arcing equipment, and switches out of the work area and areas sharing ventilation to reduce the possibility of severe personal injury or death when working on the fuel system.

Turn on the fuel supply at the vehicle main shutoff valve.

WARNING  To reduce the possibility of personal injury, keep hands, long hair, jewelry, and loose-fitting or torn clothing away from fans and other moving parts.

WARNING  The cooling fan will engage when the engine is started. To reduce the possibility of personal injury, do not put your hands in the path of a rotating fan.

WARNING  If natural gas leaks are present, do not store the vehicle inside or in any area that is covered. Severe personal injury can result from asphyxiation or explosion.

Operate the engine at idle and check for leaks using a gas detector, Part Number 3823984, or soap solution.

If leaks are found, close the vehicle main fuel shutoff valve, turn the key to the OFF position, and repair leaks immediately.

Operate the engine at full load and rated rpm conditions and idle.

Measure the fuel pressure. Refer to Procedure 014-002.

If the pressure is below minimum specifications, verify the fuel supply pressure from the high-pressure regulator or evaporator.

Fuel pressure should hold after the engine is shut off. If the fuel pressure drops off immediately, the fuel control valve is leaking.

Check for a restricted filter or hose. Refer to Procedure 005-061.

Pressure should not drop more than 68.94 kPa [10 psi] under load.

Connect a pressure gauge with a 0- to 689-kPa [0- to 100-psi] range to the Compuchek® fitting.

The fuel pressure can also be checked using INSITE™. Primary and secondary pressures are available.

Operate the engine at full load and rated rpm conditions and idle.

Measure the fuel pressure. Refer to Procedure 014-002.

If the pressure is below minimum specifications, verify the fuel supply pressure from the high-pressure regulator or evaporator.

Check for a restricted filter or hose. Refer to Procedure 005-061.

Pressure should not drop more than 68.94 kPa [10 psi] under load.

Fuel pressure should hold after the engine is shut off. If the fuel pressure drops off immediately, the fuel control valve is leaking.