Series 50 – Section 6.8 Throttle Actuator for the Series 50G Engine

Section 6.8
Throttle Actuator for the Series 50G Engine

The throttle actuator is used to control the amount of the air and fuel mixture to the engine. A butterfly valve within the body is positioned by an electric actuator that is controlled by DDEC III.‪

Effective with January 1997 production, an improved throttle actuator replaced the former throttle actuator on all Series 50G engines in transit bus applications. ‪

Note: For optimum engine performance after replacement of the former actuator with the improved actuator, the engine must be re-programmed with the new calibration before being returned to service. Authorized Detroit Diesel distributors are properly equipped and have the trained personnel to perform this service. Failure to reprogram the engine after replacement of the former throttle actuator may result in the engine remaining in the maximum no-load idle mode after engine start-up.

Section 6.8.1
Reuse or Replacement of Throttle Actuator for the Series 50G Engine

The throttle actuator is non-serviceable and should be replaced as a unit. No adjustment is required.‪

Section 6.8.2
Removal of Throttle Actuator for the Series 50G Engine

Remove the throttle actuator as follows:‪

1. Vent fuel system; refer to "2.43.1 Venting an Operable Engine to Relieve Natural Gas Pressure" and refer to "2.43.2 Venting an Inoperable Engine to Relieve Natural Gas Pressure" .
2. Disconnect and remove the six wire power harness connector from the throttle actuator.
3. Remove the four bolts connecting the throttle actuator to the mounting bracket.
4. Remove 8 bolts and nuts attaching the throttle to the inlet and outlet tube assemblies.

Section 6.8.3
Disassembly of Throttle Actuator for the Series 50G Engine

Disassembly of the throttle actuator is not required.‪

Section 6.8.4
Cleaning of Throttle Actuator for the Series 50G Engine

Cleaning of the throttle actuator is not required.‪

Section 6.8.4.1
Inspection of Throttle Actuator for the Series 50G Engine

Inspection of the throttle actuator is not required.‪

Section 6.8.4.2
Test of Throttle Actuator for the Series 50G Engine

Test of the throttle actuator is not required.‪

Section 6.8.5
Installation of Throttle Actuator for the Series 50G Engine

Install the throttle actuator as follows: ‪

1. Secure the throttle actuator to the mounting bracket with the four bolts and washers and torque to 20 N·m (15 lb·ft).
2. Connect the six wire power harness.

   Note: If the engine was built prior to 1998 model year and has a 24–volt power supply, then a throttle jumper wiring harness must be installed between the engine throttle and the engine ECM sensor harness.

3. Install a new gasket and attach the outlet tube assembly using four bolts.
4. Install a new gasket and attach the inlet tube assembly using four bolts.

   EXPLOSION ‪

   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 (-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.

5. Run engine and check for air or air and fuel mixture leaks at the throttle and connecting hoses. Refer to "2.43.3 Leak Checking the Natural Gas Fuel System" .