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Home >> Isuzu >> 1994 >> Rodeo LS, RWD >> Repair and Diagnosis (Single Page) >> Engine Performance >> System >> Engine Controls - Basic Testing - 3.2L >> Fuel System >> Fuel Pressure & Fuel Pump Relay Test >> Fuel Pump Relay
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Fuel Pump Relay

  1. Relieve fuel system pressure. See FUEL SYSTEM PRESSURE RELEASE  . Attach Fuel Pressure Gauge Set (J-34730-1 ) and Adapter (J-35957-1 ) to outlet side of fuel filter. Disconnect pressure regulator vacuum hose. Turn ignition on. Allow fuel pump to run for about 2 seconds.
  2. Fuel system pressure should be about 41-46 psi (2.8-3.2 kg/cm2 ). Start engine and check for leaks. Connect pressure regulator vacuum hose. If engine will not start, fuel pump relay can be by-passed. Also see CHART A-3, ENGINE CRANKS BUT WILL NOT RUN  under TROUBLE SHOOTING CHARTS. With engine idling, fuel pressure should be 25-30 psi (1.8-2.1 kg/cm2 ).
    NOTE: To test fuel pump relay circuit, proceed to CHART A-5, FUEL PUMP RELAY CIRCUIT  under TROUBLE SHOOTING CHARTS.


  1. ECM supplies power to relay as long as ECM receives ignition reference signals or starter crank signal. To run fuel pump without starting engine, remove relay and jumper terminals No. 2 and 4. See Figure .
  2. To test relay, use jumper wires to ground terminal No. 4 of relay and apply battery voltage to terminal No. 2 of relay. Using ohmmeter, check for continuity between relay terminals No. 1 and 3. If continuity is not present, replace relay.
    FUEL PUMP PERFORMANCE

    Application Unregulated Pressure psi (kg/cm2 ) Regulated Pressure psi (kg/cm2 )
    Rodeo 3.2L (1) 41-46 (2.8-3.2) (2) 25-35 (1.7-2.4)
    (1) With ignition on and vacuum hose disconnected from pressure regulator.
    (2) With engine at idle or with 12-14 in. Hg vacuum manually applied to pressure regulator.
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