Fuel - Normal Pump Run-On
Number 87-6(Gasoline)-63 Date 9/87Subject: FUEL PUMP RUN-ON
1982-87 VEHICLES EQUIPPED WITH FUEL INJECTION
Some vehicles with engines equipped with Throttle-Body-Injection (TBI) or Multi-Port Fuel Injection (MPFI) fuel systems may exhibit a condition where the fuel pump continues to run for 3 to 4 seconds after the ignition is shut off.
This condition will most likely occur when a cold engine has been started, run for a very short time (oil still cold), and shut off.
This condition occurs because some engine fuel systems are wired so that when the engine oil pressure is above 4 psi, the fuel pump will continue to run via a switch in the oil pressure sensor.
Customers whose cars exhibit this condition should be assured that their vehicles are operating properly, and that the fuel control system insures that all fuel pumped to the engine after shut-off is returned to the fuel tank. NO REPAIR SHOULD BE ATTEMPTED.
If the fuel pump continues to run for significantly longer than 3 to 4 seconds after the ignition is shut off, refer to Service Manual Vacuum and Wiring Diagrams/Electronic Fuel Injection/Fuel and Idle Speed Control Wiring Circuit for wiring information and to section 8A of the chassis service manual for information on diagnosis and repair/ replacement of the oil pressure sensor switch.