Skip to main content


The following criteria apply to all fuel hoses used on a Series 50G engine: ‪

  • All fuel supply hoses must be properly specified per the operating pressure and temperature requirements. Typically, pressure at fuel tanks is 3600 PSIG, pressure into the GFI regulator is 500 PSIG, and pressure out of regulator is 129-144 PSIA.
  • All fuel hoses must be Teflon with stainless steel braid. The hoses must have a sufficient amount of the homogenous material carbon black added to the Teflon inner core to bleed off static electricity.

Removal of Hose, Fitting and Filter for the Series 50G Engine

Prior to removal or replacement of fuel system hoses, fittings or filter, the fuel system must be vented. Refer to Section and refer to Section . ‪


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.

Refer to OEM for removal procedure for the hose, fitting and filter. ‪

Inspection of Hose, Fitting and Filter for the Series 50G Engine

Refer to OEM for inspection procedure for the hose, fitting and filter. ‪

Installation of Hose for the Series 50G Engine

DDC gives the following recommendations for hose routing as follows: ‪


To avoid injury from penetrating fluids, do not put your hands in front of fluid under pressure. Fluids under pressure can penetrate skin and clothing.

  1. Optimize for the shortest and simplest routing without conflicting with other criteria.
  2. Use routing that will not cause hoses to kink.
  3. Route hoses at least 12 in. away from all exhaust components (e.g. exhaust manifold, exhaust piping, catalytic converter, and turbocharger).
  4. Route hoses at least 6 in. away from high energy spark ignition wires to avoid electrical noise following hoses into wire harnesses or computer.
  5. Route hoses at least 3 in. away from moving vehicle parts (e.g. fan belts).
  6. Do not route hose against sharp edges or in an area where hose may rub or vibrate against vehicle parts.
  7. Route hoses such that there is a minimum 2 in. clearance when the cab or rear engine compartment door is closed.
  8. Secure all hoses with clips.

Install the fuel hoses as follows: ‪


Do not cut hoses so that installation and/or vehicle operation creates hose strain that may cause hoses to pull from fittings or otherwise rupture. ‪

  1. Determine the proper routing as described previously.
  2. Remove protective caps and covers from fittings and ports.
  3. Thoroughly clean any dirt and debris from threads of fittings and sealing surfaces.


    Do not scratch or mar sealing surfaces. Scratches can cause poor seals and subsequent gas leaks. ‪

  4. Connect the fitting nut into port threads and position hose as desired. Hand tighten nut.

    Note: When tightening the nut, fitting and hose may "travel" clockwise. Position hose and fitting a few degrees counter clockwise from desired position.

  5. Torque nut. Do not over tighten. Torque specifications are listed in Table .


    Always use wrench flats to tighten. Never use barbed fitting end to torque or tighten or prevent fitting rotation during tightening. Always use proper tools. Do not use pliers. Do not clamp or apply leverage to regulator parts (i.e. high pressure solenoid). Do not clamp or apply leverage to compuvalve solenoids and injectors. Do not clamp or apply leverage to filter.


    Swivel Torque, lbft

    Swivel Torque, Nm

    Lock Nut Torque, lbft

    Lock Nut Torque, Nm

    2 ‪

    6 ‪

    8 ‪

    6 ‪

    8 ‪

    3 ‪

    6 ‪

    8 ‪

    6 ‪

    8 ‪

    4 ‪

    10 ‪

    14 ‪

    8 ‪

    11 ‪

    5 ‪

    15 ‪

    20 ‪

    10 ‪

    14 ‪

    6 ‪

    20 ‪

    27 ‪

    13 ‪

    18 ‪

    8 ‪

    30 ‪

    41 ‪

    21 ‪

    28 ‪

    10 ‪

    40 ‪

    54 ‪

    33 ‪

    45 ‪

    12 ‪

    70 ‪

    95 ‪

    48 ‪

    65 ‪

    14 ‪

    80 ‪

    108 ‪

    56 ‪

    76 ‪

    16 ‪

    90 ‪

    122 ‪

    63 ‪

    85 ‪

    20 ‪

    120 ‪

    163 ‪

    80 ‪

    108 ‪

    24 ‪

    131 ‪

    178 ‪

    110 ‪

    149 ‪

    32 ‪

    300 ‪

    407 ‪

    230 ‪

    312 ‪

    Torque Values for Tube and Pipe Fittings


    To avoid injury from an explosion of natural gas, the following precautions must be taken:

    • Do not smoke when installing or servicing the engine or fuel system.
    • Installation or servicing of natural gas equipment must only be conducted in well ventilated, natural gas-compatible areas. Do not install or service equipment in an enclosed area where ignition sources are present without first ensuring that an undetected gas leak may be safely vented without being ignited.
    • Bleed natural gas lines before installing or servicing any component connected to the fuel lines.
    • Natural gas fuel systems are pressurized. Relieve pressure from any fuel system component prior to installation or service of that component.
    • 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 (-260 F [-162 C]) 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.
  6. Check for and eliminate external leaks, refer to Section . DO NOT tighten fittings to stop leaks; proper torque is sufficient with clean threads and using a new copper washer.