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HOMESERVICE MANUALSISUZU1992RODEO LS, 4WD, STANDARDREPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCETESTING & DIAGNOSISENGINE CONTROLS - BASIC TESTINGDIAGNOSTIC CHARTSCHART A-7 - FUEL SYSTEM PRESSURE TEST (3.1L)NOTES
1992 Isuzu Rodeo LS, 4WD, Standard

Chart A-7 - Fuel System Pressure Test (3.1L): Notes

1992 Isuzu Rodeo LS, 4WD, StandardSECTION Notes

If there are no RPM reference pulses, ECM will shut off fuel pump within 2 seconds after key is turned on. The fuel pump test terminal (Black/Red wire) is located on left side of engine compartment. When engine is stopped, pump can be turned on by applying battery voltage to test terminal.

NOTE: Test numbers refer to test numbers on diagnostic chart.
  1. Fuel pressure should be noted while fuel pump is running. Fuel pressure drops immediately after fuel pump stops running due to a controlled bleed in fuel system.
  2. Low fuel pressure falls into 2 categories:
    • Regulated Pressure Less Than 9 psi (.63 kg/cm2 ) Amount of fuel to injectors is okay, but pressure is too low. Fuel system will be running lean and may set Code 44. Also exhibits hard starting cold and poor overall performance.
    • Restricted Flow Causing Pressure Drop Normally, a vehicle with a fuel pressure of less than 9 psi (.63 kg/cm2 ) at idle will not be driveable. However, if pressure drop occurs only while driving, engine will normally surge, then stop, as pressure begins to drop rapidly.
  3. Restricting fuel return line allows fuel pump to develop its maximum pressure (dead head pressure). When battery voltage is applied to fuel pump test terminal, pressure should be 13-18 psi (90-124 kg/cm2 ).
  4. This test determines if high fuel pressure is due to a restricted fuel return line or a throttle body pressure regulator problem.
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