Fuel Injector Balance Test
CAUTION:
To reduce risk of fire and personal injury, wrap a shop towel around fuel pressure connection. Towel will absorb any fuel leakage that occurs during connection of fuel pressure gauge. Place towel in an approved container when connection of fuel pressure gauge is complete.
NOTE:
Fuel injector Tester (J 39021) and Injector Switch Box (J 39021-90) are required for testing on all models.
NOTE:
Fuel Injector Balance Test checks the mechanical (fuel delivery) portion of the fuel injector. An engine cool-down period of 10 minutes is necessary to avoid irregular fuel pressure readings due to "Hot Soak" fuel boiling.
- Perform On-Board Diagnostics II (OBD-II) System Check. See ON-BOARD DIAGNOSTICS II (OBD-II) SYSTEM CHECK under SELF-DIAGNOSTICS in appropriate SELF-DIAGNOSTICS article. After performing OBD-II system check, go to next step.
- Turn ignition off. Release fuel system pressure. See FUEL SYSTEM PRESSURE RELEASE . Connect Fuel Pressure Gauge (J 34730-1) or equivalent to test port on injector rail. Turn ignition on. Using scan tool, command fuel pump ON. Place bleed hose of fuel pressure gauge in an appropriate container. Bleed air from hose. With fuel pump running observe fuel pressure gauge until highest pressure is observed. Fuel pressure should be 43-55 psi (296-376 kPa). If fuel pressure is within specifications, go to next step. If fuel pressure is not within specifications, see FUEL SYSTEM DIAGNOSIS procedure in BASIC DIAGNOSTIC PROCEDURES article.
- Turn fuel pump off. Observe fuel pressure for several minutes. If fuel pressure drops a little and then remains constant, go to next step. If fuel pressure does not perform as specified, see FUEL SYSTEM DIAGNOSIS procedure in BASIC DIAGNOSTIC PROCEDURES article.
- Turn engine off. Disconnect fuel injector tester 5 or 7-pin in-line harness connector. In-line harness connector is located near front of valve cover and is identified by Blue locking plate. Connect Fuel Injector Tester (J 39021-5V) and Injector Switch Box (J 39021-90) to fuel injector harness. See Fig 1. Set amperage supply selector switch of Fuel Injector Tester to 0.5-2.5 amp position, and go to next step.
- Using scan tool, command fuel pump ON until fuel pressure is fully pressurized. Turn fuel pump Off. Record fuel pressure. Energize first fuel injector by depressing PUSH TO START TEST button on fuel injector tester. Record fuel pressure after fuel pressure gauge needle stops moving. See Fig 1.
- Repeat previous step for remaining fuel injectors. Subtract second pressure reading from first reading for each injector. The difference in readings is pressure drop value. Record pressure drop value for each fuel injector.
Add all pressure drop values to obtain total pressure drop. Divide total pressure drop by number of fuel injectors. If any individual injectors pressure drop is more or less than 1.5 psi (10 kPa) when compared against average pressure drop, go to next step. If all individual injector pressure drops are within specification, go to FUEL INJECTOR COIL TEST .
- Retest any fuel injector that does not perform as specified. If faulty fuel injector pressure drop value is still not as specified, replace fuel injector. See FUEL RAIL & FUEL INJECTORS in REMOVAL, OVERHAUL & INSTALLATION article.
NOTE:
DO NOT repeat any portion of test before running engine to prevent flooding.