Injector solenoid test: system operation description:
Use this procedure to troubleshoot the electrical system if a problem is suspected with the injectors or if any one of the diagnostic codes in Table 1 is active or easily repeated.
Perform this procedure under conditions that are identical to the conditions that exist when the problem occurs. Typically, problems with the injector solenoid occur when the engine is warmed up and/or when the engine is under vibration (heavy loads).
These engines have Electronic Unit Injectors (EUI) that are mechanically actuated and electronically controlled. The ECM sends a 105 volt pulse to each injector solenoid. The pulse is sent at the proper time and at the correct duration for a given engine load and speed. The solenoid is mounted on top of the fuel injector body.
If an open is detected in the solenoid circuit, a diagnostic code is generated. The ECM continues to try to fire the injector. If a short is detected, a diagnostic code is generated. The ECM will disable the solenoid circuit. The ECM will periodically try to fire the injector. If the short circuit remains, this sequence of events will be repeated until the problem is corrected.
Note: Refer to Illustration 2. Two injector solenoids share a supply wire. For this reason, an open circuit or a short circuit in a supply wire or a connector could cause diagnostic codes for two injector solenoids. Note that a diagnostic code for a single injector indicates that the problem is most likely in the return wire or a connector in the return circuit.
Caterpillar Electronic Technician (ET) includes the following tests that aid in troubleshooting the injector solenoids:
"Cylinder Cutout Test"
The "Cylinder Cutout Test" is used on an engine in order to determine the individual cylinder performance while the engine is running. As one or more cylinders are cut out during the test, the "Cylinder Cutout Test" uses the "Fuel Position" of each injector in order to evaluate the performance of the remaining cylinders that are firing. As the different cylinders are cut out, a comparison of the change in "Fuel Position" is used to identify cylinders that are weak or misfiring. One reason for a cylinder that is weak or misfiring is an injector that is malfunctioning mechanically.
During the test, when a good injector is cut out, the "Fuel Position" of the remaining injectors will show a consistent change. This consistent change in the "Fuel Position" is caused by the remaining injectors that are compensating for the cut out injector. If a malfunctioning injector is cut out, the "Fuel Position" will not show a proportional change. This unbalanced change is the result of the smaller quantity of fuel that is needed to compensate for the power loss from the malfunctioning injector. The "Cylinder Cutout Test" is used to isolate a malfunctioning injector in order to avoid replacement of injectors that are in good repair.
Note: Prior to running the "Cylinder Cutout Test", all active diagnostic codes must be repaired.
"Injector Solenoid Test"
Use the "Injector Solenoid Test" to diagnose an open circuit or a short circuit in the wiring for the injector solenoids. While the engine is off, the "Injector Solenoid Test" briefly activates each injector solenoid. A good solenoid will create an audible click when the solenoid is activated. After performing the test, Cat ET will indicate the status of the solenoid as "OK", "Open", or "Short".
Electronic unit injector
Typical schematic for the injector solenoids
Test Step 1. Inspect the Electrical Connectors and the Wiring
Electrical shock hazard. The electronic unit injector system uses 90-120 volts.
ECM
(1) J1/P1 connectors
(2) J2/P2 connectors
Terminal locations at the P2 ECM connector
(P2-5) Injector 1 & 2 return
(P2-6) Injector 1 supply
(P2-12) Injector 2 supply
(P2-17) Injector 3 & 4 return
(P2-18) Injector 3 supply
(P2-22) Injector 4 supply
(P2-27) Injector 5 & 6 return
(P2-28) Injector 5 supply
(P2-34) Injector 6 supply
Terminal locations at the valve cover connector
(Terminal 1) Injector 1 supply
(Terminal 2) Injector 2 supply
(Terminal 3) Injector 3 supply
(Terminal 4) Injector 4 supply
(Terminal 5) Injector 5 supply
(Terminal 6) Injector 6 supply
(Terminal 8) Injector 5 & 6 return
(Terminal 10) Injector 3 & 4 return
(Terminal 12) Injector 1 & 2 return
Expected Result:
All connectors, pins, and sockets are completely coupled and/or inserted. The harness and wiring are free of corrosion, of abrasion, and of pinch points.
Results:
Repair: Repair the connectors or wiring and/or replace the connectors or wiring. Ensure that all of the seals are properly in place and ensure that the connectors are completely coupled. Verify that the repair eliminates the problem.
STOP
Test Step 2. Check for Logged Diagnostic Codes for the Injector Solenoids
There are no logged diagnostic codes for the injector solenoids.
Test Step 3. Perform the "Cylinder Cutout Test"
The variation of the fuel rate for all cylinders is within specifications.
Repair: If a problem with the fuel system is suspected and diagnostic codes are not active or logged, refer to Systems Operation/Testing and Adjusting for information that is related to the low pressure fuel system.
If a diagnostic code results from running the "Cylinder Cutout Test", proceed to Test Step 4.
Repair: Verify that the engine valve lash for that injector is set correctly. Rerun the "Cylinder Cutout Test". If the problem is still present, replace the injector.
Test Step 4. Perform the "Injector Solenoid Test"
All cylinders indicate "OK" on Cat ET.
Repair: The problem appears to be resolved. The problem was probably caused by a poor electrical connection in a connector.If the codes continue to be logged, refer to Troubleshooting, "Electrical Connectors - Inspect".If the engine is misfiring or if the engine has low power, refer to Troubleshooting, "Engine Misfires, Runs Rough or Is Unstable" or Troubleshooting, "Power Is Intermittently Low or Power Cutout Is Intermittent".
Test Step 5. Check the Harness between the ECM and the Valve Cover Base for an Open Circuit
Cat ET displays "Short" for each of the circuits that were jumpered.
Test Step 6. Check the Harness between the ECM and the Valve Cover Base for a Short Circuit
All of the cylinders indicate "Open" on Cat ET.
Test Step 7. Check the Injector Harness Under the Valve Cover for an Open Circuit or for a Short Circuit
Connector terminals for the injector solenoid
Note: The injector solenoid that shares the supply wire of the injector that is short circuited may indicate a false test result. Disregard this test result.
Cat ET displays "Short" for the cylinder with the jumper wire that is inserted into the harness connector. Cat ET displays "Open" when the jumper wire is removed from the harness connector.
Repair: Use a multimeter to check the resistance of the suspect injector solenoid.The correct resistance of each injector solenoid is 1.06 ± 0.05 Ohms.If the resistance of the solenoid is not within specifications, replace the faulty injector. If the four digit code that is stamped on the new injector is different from the four digit code that is stamped on the original injector, enter the new code into the ECM. Verify that the problem is resolved.If the resistance of the solenoid is within specifications the problem may be intermittent. If the problem is intermittent, refer to Troubleshooting, "Electrical Connectors - Inspect". Verify that the repair eliminates the problem.
Repair: Repair the wiring and/or the connector, when possible. Replace parts, if necessary. Verify that the problem is resolved.
Test Step 8. Check the ECM for Proper Operation
Cat ET displays "Open" for the two injectors that share the supply wire.
Cat ET displays "Short" for the two injectors that share the supply wire.
Cat ET displays the correct status for each test circuit.
Repair: Inspect the connectors for moisture and for corrosion. Repair the wiring and/or the connector, when possible. Replace parts, if necessary. Clear all diagnostic codes after you complete this test step.Verify that the problem is resolved.
Repair: There is a problem with the ECM. Replace the ECM. Refer to Troubleshooting, "ECM - Replace". Verify that the problem is resolved.