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Fuel Injectors

  1. Remove injectors but leave hoses connected. Place injectors in individual measuring containers. Operate fuel pump to build up pressure, then turn pump off.
  2. Lift air flow sensor plate half-way to operate injectors until one container has filled to 3.4 oz. (100 cc). Other container volume should not vary more than 10-20°.
  3. If one injector is outside specifications, swap hoses from it and one good injector at fuel distributor and retest. If same container is low, injector is faulty. If other container is low, fuel distributor must be replaced.
    FUEL INJECTION PRESSURE TESTING

    Application Line Pressure psi (kg/cm2 ) Warm Control Pressure psi (kg/cm2 ) Rest Pressure psi (kg/cm2 ) Nozzle Opening Pressure psi (kg/cm2 )
    Audi 5000 Turbo 72-81 (5.0-5.6) 49-55 (3.4-3.8)(1) 23-37 (1.6-2.6) 38-53 (2.7-3.7)
    Audi 4000, 5000 64-74 (4.5-5.2) 49-55 (3.4-3.8) 23-37 (1.6-2.6) 41-59 (2.9-4.1)
    BMW 320i 64-75 (4.5-5.2) 49-55 (3.4-3.8) 24 (1.7) 44 (3.1)
    Mercedes-Benz 72-81 (5.0-5.6) 49-55 (3.4-3.8)(1) 36-41 (2.5-2.8) 43 (3.0)
    Peugeot 505 64-75 (4.5-5.2) 49-55 (3.4-3.8) 38-39 (2.6-2.7) 43-59 (3.0-4.1)
    Porsche 911SC 64-75 (4.5-5.2) 49-55 (3.4-3.8) (2) 36-52 (2.5-3.6)
    Porsche 924 64-75 (4.5-5.2) 49-55 (3.4-3.8) 21-24 (1.5-1.7) 36-52 (2.5-3.6)
    Porsche 924 Turbo 78-87 (5.4-6.0) 49-55 (3.4-3.8)(3) 14 (1.0) 38-55 (2.7-3.8)
    Saab 64-75 (4.5-5.2) 49-55 (3.4-3.8) 24-34 (1.7-2.4) 43-55 (3.0-3.8)
    Volkswagen 68-78 (4.8-5.5) 49-55 (3.4-3.8) 35-38 (2.4-2.6) 46-55 (3.2-3.8)
    Volvo 4 Cyl. 64-75 (4.5-5.2) 50-56 (3.5-3.9) 24-34 (1.7-2.4) 37-51 (2.6-3.6)
    Volvo 6 Cyl. 64-75 (4.5-5.2) 45-49 (3.1-3.4) 24 (1.7) 37-51 (2.6-3.6)
    (1) Vacuum lines connected.
    (2) Information not available from manufacturer.
    (3) No Vacuum applied.
  4. Relieve system pressure and remove pressure testing gauge. Turn on pump to build up pressure. Injectors may leak slightly, but no drops should form in less than 15 seconds. If drops form, check air flow sensor plate height, sticking fuel distributor plunger, or injector opening pressure.
    Fig 1: Fuel Injector Tester
    G09345290Courtesy of NOT AVAILABLE
  5. Remove injectors from vehicle and use injector tester to determine opening pressure. Check specifications in "Pressure Testing" chart and replace injectors if faulty.