C175 Tier 4 Final Engines for Off-Highway Trucks Caterpillar

Fuel Priming Pump - Test

Usage:

793F D3T

Use this procedure to troubleshoot the electrical system if a problem is suspected with the fuel pump relay or if one of the diagnostic codes in Table 1 is active or easily repeated.

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Table 1
J1939 Codes and Description	CDL Codes and Description	Comments
931-5 Engine Fuel Supply Pump Actuator : Current Below Normal	1627-5 Fuel Pump Relay : Current Below Normal	This code indicates that there is a problem with the engine fuel priming pump relay and /or electrical circuit.
931-6 Engine Fuel Supply Pump Actuator : Current Above Normal	1627-6 Fuel Pump Relay : Current Above Normal	This code indicates that there is a problem with the engine fuel priming pump relay and /or electrical circuit.
7102-5 Engine Fuel Filter Circulating Pump : Current Below Normal	4550-5 Electric Fuel Transfer Pump Relay : Current Below Normal	The code indicates that there is a problem with the clean fuel module (CFM) fuel priming pump relay and/or electrical circuit.
7102–6 Engine Fuel Filter Circulating Pump : Current Above Normal	4550-6 Electric Fuel Transfer Pump Relay : Current Above Normal	The code indicates that there is a problem with the clean fuel module (CFM) fuel priming pump relay and/or electrical circuit.

The engine is equipped with a Clean Fuel Module (CFM) which provides extra fuel filtration along with an extra fuel lift pump to pull fuel from the fuel tank. If equipped with the CFM module, the fuel will flow from the fuel tank, to the CFM priming pump, then through the CFM filters. Once the fuel leaves the CFM primary filters, the fuel flows into the engine fuel priming pump then flows into the fuel transfer pump. The fuel is pressurized and flows through the last fuel filter block secondary filter block before entering the high-pressure pump. The fuel is sent from the high-pressure pump, to the fuel rail, then flows through the injectors into the cylinders. Refer to Systems Operation, "Fuel System Operation" for more detail.

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Illustration 1	g03812829
Schematic of the low-pressure fuel system with Clean Fuel Module. (1) CFM (2) Fuel Transfer Pump (3) High-Pressure Fuel Pump (4) Tank

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Table 2
Component	Electrical Checkout
Engine Fuel Supply Pump Actuator	Fuel Pump Relay Command Override
Engine Fuel Filter Circulating Pump (CFM)	Electric Fuel Transfer Pump Relay Override

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Illustration 2	g06101624
Typical schematic for the fuel priming pump. All the connectors may not be shown. Refer to the electrical schematic for details.

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).

Probable Causes

Codes
Open circuit
Short circuit

Recommended Actions

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Table 3
Troubleshooting Test Steps	Values	Results
1. Check for Codes A. Connect Cat^® Electronic Technician (ET) to the service tool connector. B. Download the "Warranty Report" from the engine ECM before troubleshooting or clearing any diagnostic trouble codes. C. Wait at least 30 seconds for the diagnostic codes to become active. Note: Look for an active -5 or a logged -6 code.	Codes	Result: A 931-5or 1627-5code is active or logged. Proceed to Test Step 2. Result: A 931-6or 1627-6 code is active or logged. Proceed to Test Step 3. Result: A 7102-5 or 4550-5 code is active or logged. Proceed to Test Step 4. Result: A 7102-6 or 4550-6 code is active or logged. Proceed to Test Step 5.
2. Check the Wiring for an Open Circuit A. Verify that the harness connector is free of debris, free of corrosion and securely connected. B. Disconnect the solenoid from the engine harness. C. Connect a jumper wire between the terminals of the harness connector for the suspect coil. The coil is replaced with a short circuit. D. Perform the appropriate electrical checkout. Refer to Table 2.	Open Circuit	Results: A -5 code became active during the electrical checkout. The ECM did not detect the jumper wire. There is an open circuit in the wiring between the coil and the ECM connector. There may be a problem with a connector. Repair: Repair the appropriate harness wiring or replace the appropriate harness. Results: A -6 code is activated during the electrical checkout. The ECM detected the jumper wire. There is a problem with the solenoid. Repair: Replace the solenoid. If the problem is not resolved, proceed to Test Step 3.
3. Check the Wiring for a Short Circuit A. Verify that the harness connector is free of debris, free of corrosion, and securely connected. B. Disconnect the clean fuel module (CFM) resistor from the engine harness connector. C. Perform the appropriate electrical checkout. Refer to Table 2.	Short Circuit	Results: A -6 code became active during the electrical checkout. The ECM did not detect the open circuit. There is a short circuit in the wiring between the coil and the ECM connector. There may be a problem with a connector. Repair: Repair the appropriate harness wiring or replace the appropriate harness. Results: A -5 code became active during the electrical checkout. The ECM detected the open circuit. The wiring is OK. The coil has a short circuit. Repair: Replace the solenoid. If the problem is not resolved, proceed to Test Step 4.
4. Check the Wiring Harness for an Open Circuit A. Verify that the harness connector is free of debris, free of corrosion, and securely connected. B. Disconnect the clean fuel module (CFM) resistor from the engine harness connector. C. Connect a jumper wire between terminal 1 and terminal 2 on the clean fuel module (CFM) relay wiring harness connector. D. Perform the appropriate electrical checkout. Refer to Table 2.	Open Circuit	Result: A - 5 code came active during the electrical checkout. The ECM did not detect the jumper wire. There is an open circuit in the wiring between the coil and the ECM connector. There may be a problem with the connector. Repair: Repair the appropriate harness wiring or replace the appropriate wiring harness. Result: A - 6 code came active during the electrical checkout. The ECM detected the jumper wire. There is a problem with the clean fuel module (CFM) relay. Repair: Replace the clean fuel module (CFM) relay. If the problem is not resolved, proceed to Test Step 5.
5. Check the Wiring Harness for a Short Circuit A. Verify that the harness connector is free of debris, free of corrosion, and securely connected. B. Disconnect the Clean Fuel Module (CFM) resistor from the engine harness connector. C. Perform the appropriate electrical checkout. Refer to Table 2.	Short circuit	Result: A - 6 code came active during the electrical checkout. The ECM did not detect the jumper wire. There is an open circuit in the wiring between the coil and the ECM connector. There may be a problem with the connector. Repair: Repair the appropriate harness wiring or replace the appropriate wiring harness. Verify that the problem is resolved. Result: A - 5 code came active during the electrical checkout. The ECM detected the jumper wire. There is a problem with the clean fuel module (CFM) resistor. Repair: Replace the clean fuel module (CFM) resistor. Verify that the problem is resolved.