Chart A-7 Poppet Nozzle Diagnosis

Chart A-7 Poppet Nozzle Diagnosis Central MFI:

Central MFI- View Of Engine Components:

CIRCUIT DESCRIPTION
The injector tester is used to turn "ON" the injector and open the poppet nozzles for a precise amount of time, thus spraying a measured amount of fuel into the manifold. This causes a drop in fuel pressure that we can record and compare to the pressure drop specification.
A injector/poppet nozzle, that drops to less than or equal to 275 kPa (39 psi) is considered faulty.

NOTE: Poppet nozzles CANNOT be cleaned.

CHART TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart:

1. Engine "cool down" period (10 minutes) is necessary to avoid irregular readings due to "Hot Soak" fuel boiling. With ignition "OFF," connect fuel gauge J 34730-1 to fuel pressure connection. Wrap a shop towel around fitting while connecting gage to avoid fuel spillage. Disconnect harness connector at intake plenum and connect injector tester J 39021, or equivalent to injector harness. Ignition must be "OFF" at least 10 seconds to complete Powertrain Control Module (PCM) shutdown cycle. Fuel pump should run about 2 seconds after ignition is turned "ON." At this point, insert clear tubing attached to vent valve into a suitable container and bleed air from gauge and hose to insure accurate gauge operation. Repeat this step until all air is bled from the gauge.

2. Turn ignition "OFF" for 10 seconds and then "ON" again to get fuel pressure to its maximum. Record this initial pressure reading. Set tool to balance test, 4 amp. Energize injector by depressing button on injector tester one time and note pressure drop at its lowest point (disregard any slight pressure increase after drop hits low point). This will determine the pressure drop, and check for a poppet nozzle stuck open.

3. Remove upper manifold assembly (with throttle body). Remove the poppet nozzles and install poppet nozzle testers J 34730-230 to poppet nozzles. Connect nozzle testers to lower manifold assembly.
Apply battery voltage to fuel pump "test" connector, using a 10 amp fused jumper wire to energize fuel pump. Pressure should be 380-420kPa (55-61 psi).
Energize injector, this will verify if the poppet nozzle opens by checking for presence of fuel spray in each tester. This will determine if you have a faulty nozzle or a basic engine problem.