Wagoneer L6-242 4.0L VIN M FI (1988)
Fuel Injector: Testing and Inspection
Fuel Injector Balance Test
NOTE: Make sure injectors have been cleaned with an approved cleaner prior to testing. The injector balance test is done to verify a balanced
distribution of fuel to all cylinders.
1.
Start by hooking up a fuel presure gauge at the schrader valve or inline before the fuel pressure regulator (refer to gauge manufacturer
instructions).
2.
Pressurize the fuel rail by turning ignition to the ON position, and energizing the fuel pump. Fuel pressure should rise to maximum working
pressure. Refer to SPECIFICATIONS.
3.
Remove injector harness connector and connect an injector pulse tester.
4.
Pulse one injector at a time. Allow pressure to rise and stabilize in between each injector tested.
NOTE: The time each injector is pulsed is very important. Each injector should be pulsed at the same time interval (example 1 ms each).
5.
The rate of drop should be even across all the injectors. All pressure drops should be within 3% of each other, if not replace the injector.
6.
If there is no pressure drop when the injector is pulsed, verify there is a good connection between the injector and pulse tester. If connection is
good, a check of the injector circuit is required.
7.
First, check the resistance of the injector, if resistance is OK verify there is power to injector by reconnecting the injector harness connector and
START engine.
8.
Use a "NOID" light to check for pulses (light off and on). If it does not light this is an indication of a problem in the injector to ECU circuit.
Refer to COMPUTERIZED ENGINE CONTROLS for further testing. If light pulses, recheck pressure drop to verify malfunction.
NOTE: It may not be possible to connect a noid light to the harness while connected to the injector. If this is the case disconnect the harness and
connect the noid light to the harness and check pulses.
