GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 1999 🢒 Regal (China) (CNG) 🢒 Body and Accessories 🢒 Wiring Systems 🢒 Fuel Pump Electrical Circuit Diagnosis

Object Number: 516952 Size: MF
Engine Controls Components
Fuel Level Sensors
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice

Circuit Description

When the ignition switch is first turned on , the PCM energizes the fuel pump relay which applies power to the in-tank fuel pump. The fuel pump relay will remain on as long as the engine is running or cranking and the PCM is receiving reference pulses. If no reference pulses are present, the PCM de-energizes the fuel pump relay within 2 seconds after the ignition is turned on or the engine is stopped.

The fuel pump delivers fuel to the fuel rail and injectors, then to the fuel pressure regulator. The fuel pressure regulator controls fuel pressure by allowing excess fuel to be returned to the fuel tank.

Diagnostic Aids

An intermittent may be caused by a poor connection, rubbed through wire insulation or a wire broken inside the insulation. Check for a poor connection or damaged harness. Inspect the PCM harness and connectors for the following items:

    •  Improper mating
    •  Broken locks
    •  Improperly formed or damaged terminals
    •  Poor terminal to wire connections
    •  Damaged harnesses

Test Description

The numbers below refer to the step numbers on the Diagnostic Table:

  1. Checks the ignition feed circuit to the fuel pump relay.

    2.

  2. Verifies that the fuel pump feed circuit is OK between the fuel pump relay and the fuel pump, and that the fuel pump can deliver adequate pressure to the fuel rail.

    3.

  3. Checks the fuel pump feed circuit for a short to battery positive voltage.

    4.

  4. Checks whether the problem is being caused by an open in the fuel pump feed circuit or the fuel pump ground circuit.

Step

Action

Value(s)

Yes

No

1

Did you Perform the Powertrain On-Board Diagnostic (OBD) System Check?

--

Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check

2

  1. Replace the fuel pump fuse, if necessary.
  2. Disconnect the fuel pump relay.
  3. Connect a test lamp between the relay switch feed circuit at the fuel pump relay connector and a known good ground.
  4. Turn ON the ignition, with the engine OFF.

Does the test lamp illuminate?

--

Go to Step 3

Go to Step 7

3

  1. Turn OFF the ignition.
  2. Connect a 10 amp fused jumper wire between the fuel pump feed circuit and the relay switch feed circuit at the fuel pump relay connector.

    3. Caution: Wrap a shop towel around the fuel pressure connection in order to reduce the risk of fire and personal injury. The towel will absorb any fuel leakage that occurs during the connection of the fuel pressure gage. Place the towel in an approved container when the connection of the fuel pressure gage is complete.

  3. Install a J 34730-1A Fuel Pressure Gauge.
  4. Turn ON the ignition, with the engine OFF.
  5. Observe the fuel pressure gauge.

Does the pressure measure between the specified values.

338-380 kPa (49-55  psi)

Go to Step 4

Go to Step 8

4

Connect a test lamp between the fuel pump feed circuit at the fuel pump relay connector and a known good ground.

Does the test lamp illuminate?

--

Go to Step 5

Go to Step 6

5

Test the fuel pump feed circuit for a short to voltage. Refer to Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 14

--

6
  1. Inspect for a poor terminal connection at the fuel pump relay.
  2. If a problem is found, replace terminal(s) as necessary. Refer to Intermittents and Poor Connections Diagnosis and Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 14

Go to Step 11

7

Repair the open or short to ground in the fuel pump relay switch feed circuit. Refer to Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 14

--

8

  1. Leave the fused jumper wire connected.
  2. Disconnect the fuel pump.
  3. Connect a test lamp between the fuel pump feed circuit at the fuel sender harness connector and a known good ground.

Does the test lamp illuminate?

--

Go to Step 10

Go to Step 9

9
  1. Repair the open or short to ground in the fuel pump feed circuit. Refer to Wiring Repairs .
  2. Replace the fuse if necessary.

Did you find and correct the condition?

--

Go to Step 14

Go to Step 12

10

Repair the open in the fuel pump ground circuit. Refer to Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 14

Go to Step 12

11

Replace the fuel pump relay.

Did you complete the replacement?

--

Go to Step 14

--

12

Repair the fuel pump harness for an external open or short between the fuel pump connector and the fuel pump. Refer to Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 14

Go to Step 13

13

Replace the fuel pump. Refer to Fuel Sender Assembly Replacement .

Did you complete the replacement?

--

Go to Step 14

--

14
  1. Turn ON the ignition, with the engine OFF.
  2. Observe the fuel pressure gauge.

Does the fuel pressure measure between the specified values?

284-325 kPa (41-47 psi)

System OK

Go to Step 2