3512C Engines for 785C Off-Highway Trucks with Dynamic Gas Blending Caterpillar

Fuel Rail Pressure Problem - Gas

Usage:

3512 8BR

Use this procedure to troubleshoot a problem with a fuel rail pressure. Also, use this procedure if one of the following event codes is active or logged.

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Table 1
J1939 Code and Description	CDL Code and Description	Comments
7021-10 Engine Fuel #2 Injector Metering Rail #1 Pressure : Abnormal Rate of Change	E1467 (1) Fuel Rail #2 Pressure Not Responding	Fuel rail pressure has been detected as abnormal. Gas blending will not be enabled until the condition is resolved.
7021-15 Engine Fuel #2 Injector Metering Rail #1 Pressure : High - least severe (1)	E1640 (1) High Engine Fuel #2 Injector Metering Rail Pressure	Fuel rail pressure has been detected at pressures greater than system requirements.
7021-16 Engine Fuel #2 Injector Metering Rail #1 Pressure : High - moderate severity (2)	E1640 (2) High Engine Fuel #2 Injector Metering Rail Pressure	Fuel rail pressure has been detected at pressures greater than system requirements.
7021-18 Engine Fuel #2 Injector Metering Rail #1 Pressure : Low - moderate severity (2)	E1639 (2) Low Engine Fuel #2 Injector Metering Rail Pressure	Fuel rail pressure has fallen below the minimum required pressure threshold.

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Table 2
Associated Codes
J1939	CDL	Troubleshooting Procedure
6646-15	E221 (1)	Troubleshooting, "Fuel Pressure Is High (Gas Supply)"
6646-17	E222 (1)	Troubleshooting, "Fuel Pressure Is Low (Gas Supply)"

Electrical Checkouts on the Cat^® Electronic Technician (ET)

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Table 3
Component	Electrical Checkout
Gas Shutoff Valve	Engine Fuel Shutoff Valve #1 Control Override⁽¹⁾

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⁽¹⁾	The gas supply pressure must be 150 kPa (22 psi) or less to allow activation of the override.

Gas rail pressure is constantly being monitored by the engine monitoring system. Prior to enabling gas blending, the system will initiate a system health check on the integrity of the gas fuel rail and associated components. During this time, the Gas Shutoff Valve (GSOV) is cycled ON then OFF to provide gas pressure to the rail. Observation in the rise and fall of system pressure is measured at this time. If conditions are detected which indicate there is a problem with the integrity of the gas fuel train, a 7021-10 Engine Fuel #2 Injector Metering Rail #1 Pressure : Abnormal Rate of Change is activated.

Probable Causes

Codes
Supply pressure
Pressure regulator

Recommended Actions

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Table 4
Troubleshooting Test Steps	Values	Results
1. Check for Codes A. Connect Cat^® Electronic Technician (ET) to the service tool connector. B. Look for active codes that are associated with the system for the event code.	Codes	Result: An associated code is active. Repair: Troubleshoot any associated codes before continuing with this test. Result: A -10 or -18 code is active or logged. Proceed to Test Step 2. Result: A -15 or -16 code is active or logged. Proceed to Test Step 3.
2. Check the Gas Pressure A. Turn the keyswitch to the OFF position. B. Close the Liquid Natural Gas (LNG) tank isolation valve. C. Utilize chassis vent valve and safely purge gas from the gas supply line. Note: It is not recommended to use compressed air which may introduce moisture into the gas supply system. D. Connect Cat ET. E. Use Cat ET to perform the following override: - Engine Fuel Shutoff Valve #1 Control override F. Use Cat ET to monitor the status of the "Gas Supply Pressure" and "Gas Rail Pressure". Note: The pressure values should be equal.	Supply Pressure	Result: The gas supply pressure equal to the gas rail pressure. The GSOV is operating properly. Proceed to Test Step 3. Result: The gas supply pressure did not equal to the gas rail pressure and remained at 0 +/- 0.2 PSI. Repair: The GSOV is not opening properly. Repair or replace the GSOV. If the problem is not resolved, proceed to Test Step 3.
3. Check the Gas Pressure Regulator A. Connect Cat ET. B. Use Cat ET to perform the following override: - Engine Fuel Shutoff Valve #1 Control override C. Use Cat ET to monitor the status of the "Gas Rail Pressure".	Pressure Regulator	Result: The gas rail pressure is observed as higher or lower than specification. Repair: Adjust the gas pressure regulator. Refer to Testing and Adjusting, Fuel Pressure - Test (Gas System) for additional information. After adjusting the gas pressure regulator, the gas rail pressure now is within specification. The gas rail pressure is not within specifications after adjusting the gas pressure regulator. Repair or replace the gas pressure regulator. Result: The gas rail pressure is within specification. A leak in the gas fuel train after the regulator has been detected by the "Rail Integrity Check" function. Repair: Repair or replace damaged gas fuel train components.

If the procedure did not correct the issue, contact your Cat dealer Technical Communicator (TC). For further assistance, your TC can confer with the Dealer Solutions Network (DSN).