Series 50G/60G Troubleshooting – Section 3.5 Fuel System

Section 3.5
Fuel System

The Series 50G or Series 60G DDEC Engine Fuel System consist of the Low Pressure Fuel Shut-Off Valve, the fuel line, and primary and secondary Fuel Filters. ‪

Section 3.5.1
Low Pressure Fuel Shut-Off Valve Check

Check the Low Pressure Fuel Shut-Off Valve power during cranking as follows:‪

1. Turn on the ignition.
2. Crank the engine over.
3. During cranking, check the T3 output using the DDR or DDDL.
   1. If DDR or DDDL indicates T3 output is “ON”, go to step .
   2. If DDR or DDDL indicates T3 output is “OFF”, then verify with a voltmeter that wire 562 (orange) voltage is 12 or 24 V (as electrical system requires) at the ECM.
   3. If wire 562 (orange, T3 output) voltage is below 12 or 24 V (as electrical system requires), the replace the ECM.
4. During cranking, check voltage at solenoid with a voltmeter.
   1. If voltage is below 12 or 24 V (as electrical system requires), then check the vehicle wiring. Refer to OEM Vehicle Manual.
   2. If voltage is 12 or 24 V (as electrical system requires), then check the solenoid for clicking during cranking.
   3. If there is no clicking, then depressurize Fuel System (refer to "3.5.2 Depressurization of the Fuel System" ), replace the Low Pressure Fuel Shut-Off Valve, and leak check the Fuel System (refer to "3.5.4 Leak Check of the Fuel System" ).
   4. If there is clicking, then depressurize Fuel System (refer to "3.5.2 Depressurization of the Fuel System" ) and check the Fuel Filters (refer to "3.5.3 Inspection of the Fuel System" ).

Section 3.5.2
Depressurization of the Fuel System

Vent the natural gas pressure downstream of the shutoff valve as follows:‪

1. Shut off the manual valves on the natural gas supply tanks and main shutoff valve on natural gas fuel supply line.
2. Disconnect vehicle batteries using switch(es) in battery compartment or by disconnecting the battery ground cable.
3. Ensure gage pressure at point on the natural gas fuel line to be vented has been reduced to zero. If gage pressure not zero, repeat steps 1 and 2 .
4. Slightly loosen the CNG or LNG fuel line fitting to be serviced in a well-ventilated area to allow any remaining gas to vent.
5. Completely open the fitting that was slightly opened and allow to vent in a well-ventilated area.

Section 3.5.3
Inspection of the Fuel System

Inspect the Fuel System as follows:‪

1. Remove the primary and secondary Fuel Filters. Inspect for contamination or residue plugging the inside of the filter.
   1. If the primary or secondary Fuel Filter is contaminated or plugged with residue, replace with a new filter element.
   2. If not contaminated, reinstall the filter element.
2. Remove the Low Pressure Fuel Shut-Off Valve and inspect for a blocked passageway.
   1. If the valve is plugged with residue, replace with a new Low Pressure Fuel Shut-Off Valve.
   2. If not plugged, reinstall the Low Pressure Fuel Shut-Off Valve.
3. Disconnect the fuel line and inspect for a blocked passageway.
   1. If the fuel line is plugged with residue, clear fuel line or replace with a new fuel line.
   2. If not plugged, reconnect the fuel line.

Section 3.5.4
Leak Check of the Fuel System

Leak check the Fuel System as follows:‪

1. Spray soapy water or commercially available leak checking solutions on connections which are pressurized to working pressure. Look for bubbles indicating there is a leak.
2. Repair any leak found by:
   1. Tightening connection using the fitting manufacture's recommended technique.
   2. Replacing leaking component.
   3. Replace the pipe threaded connector with a new one. If the leak is a pipe thread connection, use anaerobic sealant with Teflon® (such as SWAK®) applied to the threads.
3. Recheck connections with the procedures in steps 1 and 2 .
4. Use a combustible gas detector to check for the presence of natural gas. If natural gas is detected, continue looking for leaks until the locations of all the leaks are determined.
5. If the engine still has low power, misfiring, or rough running, check the PSV assembly, refer to "3.6 Psv Assembly" .
6. If the engine operates normally, troubleshooting is done.