Series 50G & 60G Troubleshooting

Section 2.6 Psv Assembly

Section 2.6
Psv Assembly

The Pulse Width Modulated Stepper Motor Valve (PSV) biases gas flow to the venturi mixer to control the air fuel ratio. See Figure "Pulse Width Modulated Stepper Motor Valve and Fuel Mixer" . The following PSV component procedures are used to diagnose a natural gas Series 50G or Series 60G DDEC Engine which stalls.‪

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 1. PSV‪

 5. Fuel Mixer‪

 2. Bolt‪

 6. Connector O-rings‪

 3. Washer‪

 7. Fuel Transfer Tube‪

 4. PSV O-ring‪

Figure 1. Pulse Width Modulated Stepper Motor Valve and Fuel Mixer

Section 2.6.1
PSV Operation Check

Check for proper PSV operation during cranking as follows:‪

  1. Connect the DDR or DDDL and display PWM No. 3 position and Gas Valve position.
  2. Crank the engine and read PWM No. 3 position and Gas Valve position.
  3. If PWM No. 3 position indicates 26–50 % andGas Valve position indicates 50–80 % but the engine still stalls, then replace the low pressure regulator. Refer to "2.6.3.2 Throttle Assembly Procedure" .
  4. If PWM No. 3 position indicates 26–50 % and Gas Valve position is not moving, then check the PSV power and PWM No. 3 output as follows:
    1. Measure the voltage at the PSV connector, see Figure "PSV Connector" with a voltmeter. Connect positive lead to wire 446 (red, pin A) and negative lead to wire 150A (black, pin B).
      Click to see this graphic in a separate window

      Figure 2. PSV Connector

    2. If there is no voltage, check the Engine Sensor Harness (ESH) and PSV connector. Refer to DDEC III/IV Single ECM Troubleshooting Guide 6SE497. Repair or replace the ESH as necessary.
    3. If there is a voltage, check the PWM No. 3 output. Connect the voltmeter positive lead to wire 910 (orange, pin H) and negative lead to wire 150A (black, pin B) in PSV connector, see Figure "PSV Connector" . With the DDR or DDDL, slew the PWM No. 3 output from 10 % to 50 % and then to 90 %.
    4. If there is a change in voltage, then troubleshoot the PSV assembly, refer to "2.6.2 PSV Assembly Troubleshooting" .
    5. If there is no change in voltage, then troubleshoot the ESH and PSV connector. Refer to DDEC III/IV Single ECM Troubleshooting Guide 6SE497. Repair or replace the ESH as necessary.
  5. If PWM No. 3 does not move, check for voltage using a voltmeter. Connect the positive lead to wire 446 (red, pin A) and negative lead to 910 (orange, pin H), see Figure "PSV Connector" .
    1. If there is no voltage, replace the ECM and then follow the Fuel System Learn Procedure. Refer to "2.7 Fuel System Learn Procedure" .
    2. If there is a voltage, then troubleshoot the PSV assembly, refer to "2.6.2 PSV Assembly Troubleshooting" .
  6. If the gas valve does not move from 0 %, check the voltage using a voltmeter. Connect positive lead to wire 446 (red, pin A) and negative lead to wire 150A (black, pin B) of the PSV connector, see Figure "PSV Connector" .
    1. If there is a voltage at the PSV connector, then troubleshoot the PSV assembly, refer to "2.6.2 PSV Assembly Troubleshooting" .
    2. If there is no voltage, then troubleshoot the ESH, PSV connector, and. the OEM power harness. Refer to DDEC III/IV Single ECM Troubleshooting Guide 6SE497. Repair or replace the ESH and the OEM power harness as necessary.
  7. If the Gas Valve position moves but appears to have sluggish or erratic movement, check voltage at the PSV connector with a voltmeter. Connect positive lead to wire 446 (red, pin A) and negative lead to wire 150A (black, pin B), see Figure "PSV Connector" .
    1. If there is less than 10 volts, charge the batteries.
    2. If 10-12 volts are present during cranking, then troubleshoot the PSV assembly, refer to "2.6.2 PSV Assembly Troubleshooting" .

Section 2.6.2
PSV Assembly Troubleshooting

Troubleshoot the PSV assembly as follows:‪

  1. Remove PSV from engine. Do not unplug electronic connector.
  2. Remove 13 mm plug and install digital dial indicator (Mitutoyo® Digimatic Indicator, part No. 575-123 or equivalent).

    Mitutoyo® is a registered trademark of Mitutoyo Manufacturing Co., LTD.‪

  3. Plug in DDR or DDDL and go to activate outputs. Input 0 % PWM to PWM No. 3.
  4. Set digital indicator to 0 mm (0 in.).
  5. Input values listed in Table "PWM No. 3 Input and Acceptable Travel" from column 1 to PWM No. 3 with the DDR or DDDL.

    PWM No. 3 Reading‪

    Programmed Travel‪

    Travel Limits‪

    0 %‪

    0 mm (0 in.)‪

    10 %‪

    1 mm (0.04 in.)‪

    0.9–1.1 mm (0.035–0.043 in.)‪

    50 %‪

    5 mm (0.20 in.)‪

    4.9–5.1 mm (0.193–0.201 in.)‪

    100 %‪

    10 mm (0.39 in.)‪

    9.9–10.1 mm (0.390–0.398 in.)‪

    Table 2. PWM No. 3 Input and Acceptable Travel

    Note: Column 2 shows the programmed travel and column 3 shows the limits of acceptable travel.

  6. If the PSV assembly shows any of the following failure modes, then replace the PSV assembly (refer to "2.6.3 Replacing the Throttle" ), and perform the Fuel System Learn Procedure (refer to "2.7 Fuel System Learn Procedure" ).
    1. PSV remains at or below approximately 50 % of travel.
    2. PSV piston does not move (indicator reads zero throughout).
    3. PSV moves slowly or does not move to the value listed in Table "PWM No. 3 Input and Acceptable Travel" , Column 3.
    4. PSV exhibits erratic operation.
  7. If engine no longer stalls, troubleshooting is complete.

Section 2.6.3
Replacing the Throttle

Use the bolt loosening and tightening sequences and the throttle assembly procedure in the following sections when replacing the throttle. Refer to "2.6.3.1 Bolt Tightening Sequence" for the bolt loosening and tightening sequences and refer to "2.6.3.2 Throttle Assembly Procedure" for the throttle assembly procedure.‪

Section 2.6.3.1
Bolt Tightening Sequence

Loosen the bolts using the following sequence.‪

  1. Loosen the four bolts that attach the intake elbow to the rear of the throttle.
  2. Loosen the four bolts that attach the Mixer/PSV assembly to the front of the throttle.
  3. Loosen the two bolts that attach the low pressure regulator to the intake elbow.
  4. Loosen the four bolts that attach the throttle to the throttle bracket.

Tighten all the bolts using the following sequence:‪

Note: Torque for all bolts is 34 N·m (25 ft·lb).

  1. Tighten the two bolts from the throttle bracket to the gear case.
  2. Tighten the one bolt from the throttle bracket to the cylinder head.
  3. Tighten the four bolts from the Mixer/PSV assembly to the throttle.
  4. Tighten the four bolts from the throttle to the inlet elbow.
  5. Tighten the two bolts from the low pressure regulator.
  6. Tighten the two bolts from the throttle bracket to the inlet elbow.
  7. Tighten the four bolts from the bottom of the throttle bracket to the throttle.
Section 2.6.3.2
Throttle Assembly Procedure

Replace the throttle assembly as follows:‪

  1. Install the inlet elbow to the throttle body flange with the flow arrow on the throttle body pointing towards the inlet elbow. Attach with four bolts but do not tighten. See Figure "Assembling the Throttle — Series 50G" .
    Click to see this graphic in a separate window

     1. Fuel Pressure Sensor‪

     9. Washer‪

     2. Low Pressure Regulator‪

    10. PSV O-ring‪

     3. Elbow‪

    11. Bolt‪

     4. Balance Line‪

    12. Mixer Assembly‪

     5. Fuel Transfer Tube‪

    13. Gasket‪

     6. O-rings‪

    14. Throttle Body‪

     7. PSV‪

    15. Inlet Elbow‪

     8. Bolt‪

    16. Air Temperature Sensor‪

    Figure 3. Assembling the Throttle — Series 50G

  2. Install mixer assembly and gasket to opposite flange with four bolts but do not tighten.
  3. Attach the PSV and O-ring to the mixer with four Allen head screws but do not tighten.
  4. Lubricate O-rings used with fuel transfer tube with Lubriplate® prior to assembly.

    Lubriplate® is a registered trademark of Fiske Brothers Refining Company.‪

  5. Install O-rings to fuel transfer tube. Apply Teflon® liquid pipe sealant to threads.

  6. Thread fuel transfer tube into regulator and tighten.

    Note: The fuel transfer tube must thread into the regulator just far enough so the O-ring seal does not bottom out in the PSV valve and cut the seal when the regulator is bolted to the inlet elbow.

  7. Install the low pressure regulator and fuel transfer tube into the PSV. Bolt regulator to inlet elbow with two bolts but do not tighten.
  8. Install throttle, PSV, mixer and inlet elbow to engine positioning inlet hose over inlet elbow and inlet manifold. Rest the throttle on the throttle bracket. See Figure "Throttle, Bracket, and Inlet Elbow Assembly — Series 50G" .
    Click to see this graphic in a separate window

     1. Bolt‪

     7. Air Temperature Sensor‪

     2. Throttle Bracket‪

     8. Inlet Elbow‪

     3. Gear Case Cover-to-Bracket Bolts‪

     9. Clamp‪

     4. Throttle Actuator‪

    10. Hose‪

     5. Bushing‪

    11. Inlet Manifold‪

     6. Gasket‪

    Figure 4. Throttle, Bracket, and Inlet Elbow Assembly — Series 50G

  9. Install four bolts through the throttle bracket into the bottom of the throttle and two bolts through the side of the throttle bracket into the inlet elbow but do not tighten.
  10. Tighten the four mixer to throttle bolts at 34 N·m (25 ft·lb) torque.
  11. Tighten the four throttle to inlet elbow bolts at 34 N·m (25 ft·lb) torque.
  12. Tighten the two bolts that hold the regulator to the inlet elbow and tighten the four screws that hold the PSV to the mixer.
  13. Adjust the two bolts through the throttle bracket to the inlet elbow and the four bolts through the bottom of the throttle bracket to the throttle alternatively to ensure that there is no bind in the throttle. Torque the two brackets to the inlet elbow bolts at 34 N·m (25 ft·lb) and the four throttle mounting bolts at 34 N·m (25 ft·lb).


Series 50G and 60G Troubleshooting Guide - 6SE482
Generated on 10-13-2008

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