1997 Geo Prizm Base, AutomaticFACTORY OEM SERVICE PROCEDURE

Fuel Pressure

  1. Release fuel pressure. See FUEL SYSTEM PRESSURE RELEASE  . Disconnect negative battery cable. Remove bolt and fuel inlet hose from fuel rail.
  2. Install Adapter (J-39802-A) with gaskets and fuel inlet hose to fuel rail. See Fig 1 . Tighten adapter retaining bolt to 22 ft. lbs. (29 N.m). Install Fuel Pressure Gauge (J-34730-1A) to adapter. Reconnect negative battery cable. Connect a fused jumper wire between terminal Fp and terminal +B on underhood DLC. Turn ignition switch to ON position and allow fuel pressure to increase.
  3. Check fuel pressure. See FUEL PUMP PERFORMANCE  table. If fuel pressure is more than specified, ensure fuel return line is not plugged. If fuel return line is okay, replace fuel pressure regulator. If fuel pressure is less than specified, check for leaks in fuel line, fuel pump or fuel pressure regulator. Repair as necessary. If no leaks are found, go to next step.
  4. Start engine. Disconnect and plug fuel pressure regulator vacuum hose. Check fuel pressure. Reconnect fuel pressure regulator vacuum hose. Check fuel pressure. See FUEL PUMP PERFORMANCE  table. If fuel pressure is not as specified, repair or replace fuel pressure regulator and/or vacuum hose as necessary. Turn engine OFF and go to next step.
  5. Check fuel pressure with ignition off. Pressure should hold at more than specification for at least 5 minutes after engine is turned off. See FUEL PUMP PERFORMANCE  table. If pressure is less than specified, check for a leaking fuel pump, pressure regulator and/or fuel injectors. Replace or repair as necessary.
Fig 1: Installing Fuel Pressure Gauge
G93E78471Courtesy of GENERAL MOTORS CORP.
FUEL PUMP PERFORMANCE

KOEO (1) psi (kg/cm2 ) Engine @ Idlepsi (kg/cm2 ) (2) Hold Pressure psi (kg/cm2 )
38-44 (2.7-3.1) (3) 38-44 (2.7-3.1) (4) 21 (1.5)
(1) KOEO is ignition ON and engine OFF.
(2) Measured within one minute of engine OFF, and with ignition ON.
(3) With fuel pressure regulator vacuum hose disconnected and plugged. With pressure regulator vacuum hosed connected pressure is 31-37 psi (2.2-2.6 kg/cm2 ).
(4) Pressure should hold at more than specification for at least 5 minutes after engine is turned 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.