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Product: GENERATOR SET

Model: G3520B GENERATOR SET CWD
Configuration: G3520 Generator Set CWD00001-UP

Troubleshooting
G3520B Engines
Media Number -RENR5927-05 Publication Date -01/05/2006 Date Updated -25/05/2006

i01912588

Fuel Metering Valve

SMCS - 1741-038

System Operation Description:

The fuel metering valve is an electronic gas valve that controls the flow of fuel to the engine. The valve
works with the master Electronic Control Module (ECM) in order to ensure the correct flow of gas in all
conditions of engine operation.

The ECM sends a command signal for the flow of fuel and information about the specific gravity of the gas
to the fuel metering valve. The valve converts the command signal and the information into a valve position
that directly corresponds to the desired gas flow. The position of the valve is compensated by these additional
factors that are internal to the valve: absolute fuel pressure, differential pressure of the valve and fuel
temperature.

The fuel metering valve sends the following information to the ECM via the CAN data link: position of the
fuel valve, absolute fuel pressure, differential pressure of the valve and fuel temperature.

During normal operation, the valve receives two command signals from the ECM. One of the signals is a
digital signal that is received via the CAN data link. The other signal is a pulse width modulated signal
(PWM) that is received via a pair of wires. The valve will use the digital signal when both signals are
available.

If the PWM signal is not available, the valve will continue to use the digital signal. The ECM will activate a
1446-05 diagnostic code. Engine performance will be affected.

If the digital signal is not available, the valve will use the PWM signal. The ECM will activate a 1446-09
diagnostic code. Engine performance will be affected.

Status Indicator for the Fuel Metering Valve

Illustration 1 g00996218

Status indicator for the fuel metering valve

The fuel metering valve contains a status indicator. The indicator flashes in order to indicate the status of the
valve. The color of the indicator indicates the severity of the problem. During operation, the status indicator
will flash one of the following colors:

Green - Normal operation

Orange - The valve has detected a problem and the valve continues to operate.

Red - The valve has detected a serious problem. The valve has shut down.

The flash code indicates the particular error that has been detected by the valve. Before performing
maintenance on the valve, observe the status indicator. Refer to Installation and Operation Manual,
SEBU7630 for additional information.
Illustration 2 g00997524

Schematic for the circuit of the fuel metering valve

Test Step 1. Inspect the Electrical Connectors and Wiring

A. Set the engine control to the OFF/RESET mode. Switch the 16 amp circuit breaker OFF.

Note: For the following steps, refer to Troubleshooting, "Inspecting Electrical Connectors".
 Illustration 3 g00996091

Terminal box for the master ECM

(1) J1/P1 connectors for the master ECM

(2) J16/P16 connectors for the fuel metering valve

(3) 16 amp circuit breaker

B. Thoroughly inspect each of the following connectors:

◦ Master ECM J1/P1 connectors

◦ J16/P16 connectors for the fuel metering valve

a. Check the torque of the Allen head screw for the ECM connectors. The proper torque is 6 ± 1
N·m (55 ± 9 lb in).
Illustration 4 g00996094

Harness side of the ECM P1 connector

(P1-34) CAN data link −

(P1-42) CAN shield

(P1-50) CAN data link +

(P1-58) PWM signal for the fuel flow

(P1-60) Return

(P1-63) −Battery

(P1-65) −Battery

(P1-67) −Battery

(P1-69) −Battery
Illustration 5 g00903246

Harness side of the P16 connector

(P16-A) Switched +battery

(P16-B) CAN data link +

(P16-C) CAN data link −

(P16-D) CAN shield

(P16-E) PWM signal for the fuel flow

(P16-F) Return

(P16-H) −Battery

(P16-J) Unswitched +battery

Illustration 6 g00903247

Harness side of the P24 connector

(P24-C) CAN data link +

(P24-F) CAN data link −

(P24-K) Unswitched +battery

(P24-L) −Battery

(P24-M) Switched +battery

(P24-P) Jumper wire for the terminating resistor for the CAN data link

(P24-R) Jumper wire for the terminating resistor for the CAN data link

(P24-S) PWM signal for the fuel flow

(P24-T) Return
 b. Perform a 45 N (10 lb) pull test on each of the wires that are associated with the fuel metering
valve.

Illustration 7 g00904218

(4) P24/J24 connectors for the fuel metering valve

(5) Fuel metering valve

c. Check the wiring for abrasion and for pinch points from the fuel metering valve to the master
ECM.

Expected Result:

All of the connectors, pins, and sockets are connected properly. The connectors and the wiring do not have
corrosion, abrasion, or pinch points.

Results:

• OK - The components are in good condition with proper connections. Proceed to Test Step 2.

• Not OK - The components are not in good condition and/or at least one connection is improper.

Repair: Perform the necessary repairs and/or replace parts, if necessary. Ensure that all of the seals are
properly installed. Ensure that the connectors are properly engaged. Verify that the repair has
eliminated the original problem.

STOP

Test Step 2. Check for Diagnostic Codes

 A. Connect the Caterpillar Electronic Technician (ET) to service tool connector J23.

B. Switch the 16 amp circuit breaker ON. Set the engine control to the STOP mode.

C. Use Cat ET to determine if any of the following diagnostic codes are active:

◦ 1446-05 "Fuel Metering Module open circuit"

◦ 1446-09 "Unable to communicate with Fuel Metering Module"

◦ 1446-12 "Fuel Metering Module malfunction"

◦ 1446-13 "Fuel Metering Module calibration required"

◦ 1447-12 "Fuel Metering Sensor Module malfunction"

Expected Result:

There are no active diagnostic codes.

Results:

• OK - There are no active diagnostic codes. The signal and the communication between the master
ECM and the fuel metering valve appear to be OK at this time. However, diagnostic codes may be
logged.

Repair: If you are troubleshooting an intermittent problem, refer to Troubleshooting, "Inspecting

Electrical Connectors".

STOP

• Not OK (Active 1446-05) - The master ECM has detected an open circuit or a short circuit for the
circuit for the PWM signal between the ECM and the fuel metering valve. Proceed to Test Step 3.

• Not OK (Active 1446-09) - The master ECM has detected an open circuit or a short circuit for the
CAN data link between the ECM and the fuel metering valve. Proceed to Test Step 6.

• Not OK (Active 1446-12) - The fuel metering valve has detected an internal malfunction.

Repair: Observe the status indicator on the fuel metering valve. Refer to Installation and Operation
Manual, SEBU7630, "Raptor Gas Regulation and Metering Valve/Actuator System for Caterpillar".

STOP

• Not OK (Active 1446-13) - The fuel metering valve requires calibration.

Repair: Observe the status indicator on the fuel metering valve. Refer to Installation and Operation
Manual, SEBU7630, "Raptor Gas Regulation and Metering Valve/Actuator System for Caterpillar".

STOP

• Not OK (Active 1447-12) - There is a malfunction of the sensor module in the fuel metering valve.

Repair: Observe the status indicator on the fuel metering valve. Refer to Installation and Operation
Manual, SEBU7630, "Raptor Gas Regulation and Metering Valve/Actuator System for Caterpillar".

STOP

Test Step 3. Check the PWM Signal for the Fuel Flow
 A. Set the engine control to the OFF/RESET mode. Switch the 16 amp circuit breaker OFF.

Illustration 8 g00997043

Harness side of the ECM P1 connector

(P1-58) PWM signal for the fuel flow

(P1-60) −Battery

B. Insert two 7X-1710 Multimeter Probes into the harness side of the P1 connector. Insert the first probe
into terminal 58. Insert the second probe into terminal 60. Use a multimeter that is capable of
measuring the frequency and the duty cycle. Connect the multimeter to the probes.

C. Switch the 16 amp circuit breaker ON. Set the engine control to the STOP mode.

D. Measure the DC voltage, the duty cycle, and the frequency of the signal for the fuel flow.

Expected Result:

The DC voltage is between 13.7 and 15.7.

The duty cycle is between 92 and 98 percent.

The frequency is between 175 and 185 hertz.

Results:

• OK - The voltage, the duty cycle, and the frequency of the PWM signal for the fuel flow is correct at
the P1 connector. There is a problem with the fuel metering valve.

Repair: Replace the fuel metering valve. Verify that the repair has eliminated the original problem.

STOP

• Not OK - The voltage, the duty cycle, and/or the frequency of the signal for the fuel flow is not correct
at the P1 connector. Proceed to Test Step 4.

Test Step 4. Check the Continuity of the Circuit for the PWM Signal

A. Set the engine control to the OFF/RESET mode. Switch the 16 amp circuit breaker OFF.

B. Disconnect the J1/P1 connector.

C. Disconnect the fuel metering valve J24/P24 connector.

Illustration 9 g00997092

(P1) Connector for the ECM

(P24) Connector for the fuel metering valve

(P1-58) PWM signal for the fuel flow

(P1-60) Return

(P24-S) PWM signal for the fuel flow

(P24-T) Return

D. Use a multimeter to check the continuity of the following circuits:

 ◦ P1-58 to P24-S

◦ P1-58 to the ground strap

◦ P1-60 to P24-T

Expected Result:

The continuity of the circuits between the terminals is good.

The continuity between the terminal and the ground strap is open.

Results:

• OK - The continuity of the circuit for the PWM signal between the master ECM and the fuel metering
valve is good. The continuity of the circuit between the master ECM and the ground strap is open.
Proceed to Test Step 5.

• Not OK - One or both of the following conditions is found: There is an open circuit in the wiring for
the PWM signal between the master ECM and the fuel metering valve. There is a short circuit between
the master ECM and a component that is at ground potential.

Repair: Repair the wiring and/or connectors. Replace parts, if necessary. Ensure that all of the seals
are properly installed. Ensure that the connectors are properly engaged. Verify that the repair has
eliminated the original problem.

STOP

Test Step 5. Check the Resistance of the Internal Circuit of the Fuel Metering Valve

A. Ensure the following conditions:

◦ The engine control switch is in the OFF/RESET position.

◦ The 16 amp circuit breaker in the terminal box is OFF.

◦ The fuel metering valve J24/P24 connectors are disconnected.

 Illustration 10 g00952241

J24 connector on the fuel metering valve

(J24-S) PWM signal for the fuel flow

(J24-T) Return

B. Measure the resistance between terminals J24-S and J24-T.

Expected Result:

The resistance is between 315,000 ohms and 325,000 ohms.

Results:

• OK - The resistance is between 315,000 ohms and 325,000 ohms. Proceed to Test Step 8.

• Not OK - The resistance is not between 315,000 ohms and 325,000 ohms.

Repair: Replace the fuel metering valve. Verify that the repair has eliminated the original problem.

STOP

Test Step 6. Check the Continuity of the Wiring Harness for the Circuit of the CAN Data Link

A. Set the engine control to the OFF/RESET mode. Switch the 16 amp circuit breaker OFF.

B. Disconnect the J1/P1 and J24/P24 connectors.

Illustration 11 g00997065

(P1) Connector for the ECM

(P24) Connector for the fuel metering valve

(P1-34) Can data link −

(P1-50) Can data link +

 (P24-F) Can data link −

(P24-C) Can data link +

(P24-P) Jumper wire for the terminating resistor for the CAN data link

(P24-R) Jumper wire for the terminating resistor for the CAN data link

C. Use a multimeter to check for continuity between the points that are listed in Table 1.

Table 1
Points to Check for Continuity
Connector and Terminal Connector and Terminal
P1-34 P24-F
P1-50 P24-C
P1-34 Ground strap
P1-50 Ground strap
P24-P P24-R

Expected Result:

The continuity of the circuits between the terminals is good.

The continuity between the terminals and the ground strap is open.

The continuity between terminals P24-P and P24-R is good.

Results:

• OK - The continuity of the circuits is good. The continuity of the circuit between the master ECM and
the ground strap is open. The continuity between terminals P24-P and P24-R is good. Proceed to Test
Step 7.

• Not OK - At least one of the following conditions is found: There is an open circuit between the plug
for the master ECM and the plug for the fuel metering valve. There is a short circuit between the plug
for the master ECM and a component that is at ground potential. The continuity between terminals P24
-P and P24-R is open.

Repair: Perform the necessary repairs to the wiring and/or connectors. Replace parts, if necessary.
Ensure that all of the seals are properly installed. Ensure that the connectors are properly engaged.
Verify that the repair has eliminated the original problem.

STOP

Test Step 7. Check the Shield for the CAN Data Link

A. Disconnect the following connectors:

◦ P3

◦ P9

◦ P16
 B. Disconnect the 168-2028 Wiring Harness from the J19 connector.

C. Disconnect the Caterpillar Electronic Technician (ET) from the J23 connector.

D. Use a multimeter to check the continuity of the circuits that are listed in Table 2:

Table 2
Points to Check for Continuity
Connector and Terminal Connector and Terminal
P1-42 P3-42
P1-42 P9-a
P1-42 J16-D
P1-42 J19-G
P1-42 J23-C
P1-42 Ground strap

Expected Result:

The continuity of the circuits between the terminals is good.

The continuity between P1-42 and the ground strap is open.

Results:

• OK - The continuity of the circuits of the wire shield for the CAN Data Link is good. The continuity of
the circuit between P1-42 and the ground strap is open.

Repair: Perform the following steps:

1. Reconnect the following connectors:

◾ P3

◾ P9

◾ P16

2. Reconnect the 168-2028 Wiring Harness to the J19 connector.

3. Connect the Caterpillar Electronic Technician (ET) to the J23 connector.

Proceed to Test Step 8.

• Not OK - One or both of the following conditions is found: At least one of the circuits of the wire
shield for the CAN data link is open. There is a short circuit between the P1-42 terminal and the
ground strap.

Repair: Repair the wiring and/or connectors. Replace parts, if necessary. Ensure that all of the seals
are properly installed. Ensure that the connectors are properly engaged. Verify that the repair has
eliminated the original problem.

STOP
Test Step 8. Check the Supply Voltage to the Fuel Metering Valve

A. Switch the 16 amp circuit breaker ON. Set the engine control to the STOP mode.

Note: The "1446-05 Fuel Metering Module open circuit" and "1446-09 Unable to communicate with
Fuel Metering Module" diagnostic codes will be activated.

Illustration 12 g00952242

P24 connector on the harness for the fuel metering valve

(P24-K) Unswitched +battery

(P24-L) −Battery

(P24-M) Switched +battery

B. Use a multimeter to measure the voltage between the following terminals of the harness connector for
the fuel metering valve:

◦ P24-M and P24-L

◦ P24-K and P24-L

Expected Result:

The voltage between terminals P24-M and P24-L is between 22.0 VDC and 24.0 VDC.

The voltage between terminals P24-K and P24-L terminals is 22.0 VDC and 24.0 VDC.

Results:

• OK - The voltage is correct at the P24 connector. Reconnect the P24 connector. Proceed to Test Step
9.

• Not OK - The voltage is not correct at the P24 connector. There is an open circuit or a short circuit in
the harness to the fuel metering valve.
 Repair: Perform the necessary repairs for the wiring and/or the connectors. Replace parts, if
necessary. Ensure that all of the seals are properly installed. Ensure that the connectors are properly
engaged. Verify that the repair has eliminated the original problem.

STOP

Test Step 9. Check for a Fault Code

A. Switch the 16 amp circuit breaker ON. Set the engine control to the STOP mode.

B. Observe the "Active Diagnostic Codes" screen of Cat ET. Look for these codes:

◦ 1446-05

◦ 1446-09

Expected Result:

Neither code is active.

Results:

• OK - There is no active 1446-05 or 1446-09 diagnostic code.

Repair: Start the engine and run the engine. If the codes do not recur, the problem is resolved. The
original diagnostic code was probably caused by a poor electrical connection. If either code recurs,
refer to Troubleshooting, "Inspecting Electrical Connectors".

STOP

• Not OK - There is an active 1446-05 or 1446-09 diagnostic code.

Repair: The diagnostic code could be caused by the master ECM or by the fuel metering valve. It is
unlikely that the master ECM or the fuel metering valve has failed. Exit this procedure and perform
this procedure again. If the problem is not resolved, perform the following steps:

1. Temporarily install a new master ECM. Refer to Troubleshooting, "Replacing the ECM".

If the problem is resolved with the new ECM, install the original ECM and verify that the
problem returns. If the new ECM operates correctly and the original ECM does not operate
correctly, replace the original ECM. Refer to Troubleshooting, "Replacing the ECM". If the new
ECM does not solve the problem, reinstall the original ECM. Replace the fuel metering valve.

STOP

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