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HOMESERVICE MANUALSVOLVO1991740 BASE, 4D WAGON, AUTOMATIC, AW70LREPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCESYSTEMENGINE CONTROLS - BASIC TESTINGFUEL SYSTEMFUEL PRESSURE
1991 Volvo 740 Base, 4D Wagon, Automatic, AW70L

Fuel Pressure

1991 Volvo 740 Base, 4D Wagon, Automatic, AW70LSECTION Fuel Pressure
WARNING: ALWAYS relieve fuel pressure before disconnecting any fuel injection-related component. DO NOT allow fuel to contact engine or electrical components.

Fuel Pump Pressure

  1. Remove panel under right side of dash. Remove fuel injection system relay. See Fig 1 . Crank engine for at least 5 seconds. If engine starts, let it run until it dies. Before disconnecting, cover fuel line connector with shop towel to absorb any fuel spray.
    Fig 1: Locating Fuel Injection System Relay
    G91D16645Courtesy of VOLVO CARS OF NORTH AMERICA.
  2. Connect a fuel pressure gauge between fuel line and injection manifold. Connect jumper wire between terminals No. 30 and 87/2 of fuel injection system relay connector. See Fig 2 . Fuel pressure should be 42 psi (3.0 kg/cm2 ).
    Fig 2: Identifying Fuel Injection System Relay Terminals
    G121539Courtesy of VOLVO CARS OF NORTH AMERICA.
  3. If pressure is too low, pinch off fuel return line and recheck pressure (DO NOT allow pressure to exceed 86 psi (6.0 kg/cm2 ). If pressure rises quickly, pump and lines are functioning correctly. Replace pressure regulator and recheck pressure.
  4. If pressure rises slowly, fuel filters or lines are blocked. If pressure does not rise, pump is defective.
  5. If fuel pressure is high, disconnect fuel return line from pressure regulator and blow into line. If line is open, pressure regulator is defective and should be replaced.
  6. Pressure may also be checked with engine off and fuel gauge connected. Attach a hand-held vacuum pump to pressure regulator. Line pressure should decrease as vacuum is applied to regulator.
  7. With 12 volts applied, pump volume should be 1.1 qt (.52L) in 30 seconds.
RENDER: 1.0x

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.