Fuel Pump Circuit Wiring Diagram (1989-1991 3.3L V6 Buick Skylark, Olds Calais)

APPLIES TO: This fuel pump circuit wiring diagram applies to the following vehicles:

• 3.3L V6 Buick Skylark: 1989, 1990, 1991.
• 3.3L V6 Oldsmobile Calais (Cutlass Calais): 1989, 1990, 1991.

Fuel Pump Basic Operating Theory

When the ignition key is first turned to the ON position (without cranking the engine), the PCM energizes the fuel pump relay for about 2 seconds. This briefly powers the fuel pump to build fuel pressure before the engine is started.

If the engine is not cranked within those 2 seconds, the PCM turns the fuel pump relay back OFF. Once the engine begins cranking and the PCM detects crankshaft reference pulses, it energizes the fuel pump relay again, allowing the fuel pump to run continuously.

As a backup, the fuel pump can also receive power through the oil pressure switch. This switch is normally open and closes when engine oil pressure reaches approximately 4 PSI (28 kPa). If the fuel pump relay fails, the closed oil pressure switch can still supply power to the fuel pump once the engine develops enough oil pressure.

Keep the following points in mind when diagnosing a fuel pump or fuel pump relay problem:

• A failed fuel pump relay can cause the engine to crank longer than normal before it starts, especially when the engine is cold. This happens because the oil pressure switch must build enough oil pressure before it can power the fuel pump.
• If the fuel pump fails completely, the engine will crank but will not start.
• A weak fuel pump that cannot produce the correct fuel pressure can cause poor engine performance, such as hard starting, hesitation, lack of power, or misfires.

FUEL PUMP PRESSURE TEST: The following tutorial explains how to test the fuel pump with a fuel pressure test gauge:

• How To Test The Fuel Pump (1989-1993 3.3L V6 Buick, Oldsmobile).

ENGINE NO-START DIAGNOSTIC TESTS: Troubleshooting an engine no-start problem, the following tutorial explains the basics behind finding out what's causing the issue:

• How To Diagnose A No-Start Problem (3.3L V6 Buick, Oldsmobile).

1992-1993 FUEL PUMP CIRCUIT WIRING DIAGRAM:

• Fuel Pump Circuit Wiring Diagram (1992-1993 3.3L V6 Buick Skylark).

More 3.3L V6 Buick Century Tutorials

You can find a complete list of 3.3L V6 Buick Century tutorials and wiring diagrams in this index:

• GM 3.3L Index of Articles.

Here's a sample of the tutorials you'll find in the index:

• How To Test The Throttle Position Sensor (1989-1993 3.3L V6 Buick, Oldsmobile).
• How To Test The MAF Sensor (1989-1993 3.3L V6 Buick, Oldsmobile).
• How To Test Engine Compression (3.3L V6 Buick, Oldsmobile).
• How To Test A Blown Head Gasket (3.3L V6 Buick, Oldsmobile).