Fuel Pump - Run-On Explanation
87chevy25Number: 87-210
Section: 6C
Date: SEPT., 1987
Subject: FUEL PUMP RUN-ON
Model and Year: 1982-87 VEHICLES EQUIPPED
WITH FUEL INJECTION
TO: ALL CHEVROLET DEALERS
Some vehicles 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, (see chart).
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 Section 8A of the Chassis Service Manual for information on diagnosis and repair/replacement of the oil pressure sensor switch.
Engine Year VIN Code
2.0L Pushrod (OHV) 1983-86 P
2.0L Pushrod (OHV) 1987 1
2.5L 1982-87 R
2.5L 1982-86 2
2.8L 1985-87 S,W