1990 Geo Metro Base, 4D Hatchback, AutomaticFACTORY OEM SERVICE PROCEDURE

Fuel Pressure Test

  1. Relieve fuel system pressure. See FUEL PRESSURE RELEASE. Remove air cleaner assembly. Remove fuel inlet hose from throttle body and install Fuel Pressure Gauge (J-34730-1) with "T" Fitting Adapter (J-34730-75). See Fig 1 .
  2. Start engine. Check for leaks and repair if necessary. Allow engine to warm to normal operating temperature. Turn engine off.
    NOTE: If engine does not start, disengage fuel pump relay from main fuse box and attach jumper wire between Pink wire of connector and ground. See Fig 1 . Fuel pump should operate when ignition switch is turned to ON position.
  3. With ignition switch on and engine off, measure and record fuel pressure with pump operating. Fuel pressure should be 23-30 psi (1.6-2.1 kg/cm2 ). Start engine. Measure and record fuel pressure with engine idling. See FUEL PUMP REGULATED PRESSURE table. Fuel pressure should be 13.0-20.0 psi (0.9-1.4 kg/cm2 ). Turn ignition off.
  4. Fuel pressure should maintain 13.0 psi (0.9 kg/cm2 ) for one minute and slowly drop after fuel pump operation stops. If pressure is not within specification, check for defective fuel pump, pressure regulator or restriction in fuel system. Repair as necessary. Start engine and ensure no fuel leaks exist.
Fig 1: Checking Fuel System Pressure
G121590Courtesy of GENERAL MOTORS CORP.
REGULATED FUEL PRESSURE

Application (1) Pressure psi (kg/cm2 )
Metro 13-20 (0.9-1.4)
(1) With ignition on, engine idling and fuel pressure regulator vacuum hose connected.
UNREGULATED FUEL PRESSURE

Application (1) Pressure psi (kg/cm2 )
Metro 23-30.5 (1.6-2.1)
(1) Check with engine idling. Disconnect and plug fuel pressure regulator vacuum hose.
MAXIMUM FUEL PRESSURE

Application (1) Pressure psi (kg/cm2 )
Metro More Than 30.5 (2.1)
(1) Fuel line pinched before inlet to TBI or fuel rail.
REST FUEL PRESSURE

Application (1) Pressure psi (kg/cm2 )
Metro Less Than 13 (1.9)
(1) Ignition switch and engine off.
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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.