Series 50 – Section 2.32 High Pressure Fuel Regulator for the Series 50G Engine Prior to 1998

Section 2.32
High Pressure Fuel Regulator for the Series 50G Engine Prior to 1998

The GFI system uses a high pressure single stage regulator to control gas pressure. See Figure "High Pressure Fuel Regulator for the Series 50G Engine Prior to 1998" . Natural gas enters the regulator at the inlet port and goes through an integral 40 micron filter. Filtered gas flows to the high pressure solenoid activated valve that, when activated, allows natural gas to flow to the pressure regulator section and high pressure transducer.‪

Note: In some installations, a Tescom 500 PSI step down regulator is installed upstream of the GFI pressure regulators.

1. Relief Port‪	7. Coolant Outlet‪
2. High Pressure Sensor‪	8. Alternate Relief Port‪
3. Gas Outlet‪	9. Relief Valve‪
4. Solenoid‪	10. Gas Inlet‪
5. Coolant Inlet‪	11. Filter‪
6. Alternate‪	‪

Figure 1. High Pressure Fuel Regulator for the Series 50G Engine Prior to 1998

The regulator section uses a conventional spring-diaphragm-pintle mechanism to regulate pressure in the outlet chamber. From the outlet chamber, regulated gas is passed to the outlet port. The outlet chamber is also connected to a 175 PSIG pressure relief valve. If the outlet chamber pressure exceeds 175 PSI, the valve opens and vents to relief port or alternate relief port. The pressure regulator relief valve must be incorporated into the vehicle vent system in accordance with N.F.P.A. 52 "Compressed Natural Gas (CNG) Vehicular Fuel Systems."‪

This regulator uses a counterflow coolant circuit. Two standard ports and one alternate port are provided. Engine coolant is circulated through hoses to one port then returned through one of the other ports. The coolant must have 35°F (37°C) capability.‪

Section 2.32.1
Replacement of the High Pressure Fuel Regulator for the Series 50G Engine Prior to 1998

Prior to removal of the high pressure fuel system regulator, the fuel system must be vented. Refer to "2.36.1 Venting an Operable Engine to Relieve Natural Gas Pressure" and refer to "2.36.2 Venting an Inoperable Engine to Relieve Natural Gas Pressure" .‪

The GFI regulator is non-serviceable and should be replaced as a unit. No adjustment is required. Several different type GFI regulations are used depending on the installation type and all are very similar in appearance. When replacing a GFI regulator be certain to replace with the same part number or the correct service replacement part number regulator.‪

Section 2.32.2
Removal of the High Pressure Fuel Regulator for the Series 50G Engine Prior to 1998

Prior to removal or replacement of the high pressure fuel regulator, the fuel system must be vented. Refer to "2.36.1 Venting an Operable Engine to Relieve Natural Gas Pressure" and refer to "2.36.2 Venting an Inoperable Engine to Relieve Natural Gas Pressure" .‪

EXPLOSION ‪
To avoid injury from the explosion of natural gas, the engine must be kept in a well ventilated area away from open flames, sparks, and electrical resistance (heating) coils.‪

After the fuel system has been properly vented, remove the regulator as follows:‪

1. Disconnect the wire harness.
2. Drain cooling system.
3. Disconnect supply and return hoses at regulator.
4. Disconnect gas outlet hose at regulator gas outlet.
5. Disconnect gas inlet hose at regulator gas inlet.
6. Disconnect vent hose at regulator relief port.
7. Remove two attaching bolts to loosen the regulator from its bracket.

Section 2.32.2.1
Inspection of the High Pressure Fuel Regulator for the Series 50G Engine Prior to 1998

Inspection of the regulator is not required.‪

Section 2.32.3
Installation of the High Pressure Fuel Regulator for the Series 50G Engine Prior to 1998

Install the High Pressure Fuel Regulator as follows:‪

NOTICE:
During all operations, ensure no dirt or debris is allowed to enter unit. Tightly cap or cover all open ports and openings. Do not remove the factory caps until it is time to install the hoses.‪

1. Mount the regulator on its bracket and install 2 attaching bolts.

   NOTICE:
   The regulator must be located such that it is protected from road hazards, accidents, or any other external items that could damage the pressure regulator or adjoining fuel lines.‪

2. Connect vent hose at regulator relief port.
3. Connect gas inlet host at regulator gas inlet.
4. Connect gas outlet hose at regulator gas outlet.
5. Connect coolant supply and return hoses at regulator.
6. Refill cooling system.
7. Connect the wire harness.
8. Open manual gas shutoff valve and start engine.

   EXPLOSION ‪

   To avoid injury from an explosion of natural gas, the following precautions must be taken:‪ Use a combustible-gas detector. Liquefied natural gas (LNG) is odorless and cannot be detected by smell. Compressed Natural gas (CNG) may be odorless and may not be detected by smell. Equipment fuel systems are the responsibility of the Original Equipment Manufacturer (OEM). Equipment fuel system guidelines must be closely adhered to when installing or servicing equipment. Refer to OEM guidelines specifying which maintenance procedures require venting of fuel lines and fuel tanks. LNG systems are pressurized and contain extremely cold (-162° C [-260° F]) fluids. Contact the fuel supplier or OEM for LNG safety requirements. Contact with LNG may cause personal injury (freezing). Vent systems on the equipment should be ducted to a safe area whenever equipment is in an enclosed area.

   1. Refer to "2.36.3 Leak Checking the Natural Gas Fuel System" for leak checking procedure.