Fuel System Diagnosis. Chevrolet Cavalier 1998

For 1990-2009 cars only

Makes 🢒 Chevrolet 🢒 1998 🢒 Cavalier 🢒 Engine 🢒 Engine Controls - 2.2L 🢒 Fuel System Diagnosis


(1)	Fuel Pressure Regulator
(2)	Quick Connect
(3)	Fuel Pressure Gauge Kit J 29658 D
(4)	Fuel Hose Pinch Point
(5)	Fuel Hose Pinch Point
(6)	Quick Connect Adapter
(7)	Fuel Pressure Pipe
(8)	Fuel Return Pipe
(9)	Fuel Hose Pinch Point
(10)	Flexible Hose

Circuit Description

When the ignition switch is turned ON, the Powertrain Control Module (PCM) will turn ON the in-tank fuel pump. The in-tank fuel pump will remain ON as long as the engine is cranking or running and the PCM is receiving reference pulses. If there are no reference pulses, the PCM will turn OFF the in-tank fuel pump after 2 seconds since the ignition switch is turned ON or after 2 seconds once the engine stops running. The in-tank fuel pump is an electric pump within an integral reservoir. The in-tank fuel pump supplies fuel through an in-line fuel filter to the fuel rail assembly. The fuel pump is designed to provide fuel at a pressure above the pressure that is needed by the fuel injectors. A fuel pressure regulator, attached to the fuel rail assembly, keeps the fuel available to the fuel injectors at a regulated pressure. The unused fuel is returned to the fuel tank by a separate fuel return pipe.

Test Description

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

In order to relieve the fuel pressure, refer toFuel Pressure Relief Procedure . When the ignition is ON and the fuel pump is running, the fuel pressure indicated by the fuel pressure gauge should be 284-325 kPa (41-47 psi).

A fuel system that drops more than 5 psi in 10 minutes has a leak in one or more of the following areas:

•	The fuel pump check valve

•	The fuel pump flex pipe

•	The fuel injector(s)

Fuel pressure that drops-off during acceleration, cruise or hard cornering may cause a lean condition. A lean condition can cause a loss of power, surging, or a misfire. You can use a scan tool in order to diagnose a lean condition. If an extremely lean condition occurs, the oxygen sensors will stop toggling. The oxygen sensor output voltage(s) will drop below 500 mV. Also, the fuel injector pulse width will increase.

When the engine is idling, the manifold pressure is low (high vacuum). This low pressure (high vacuum) is applied to the fuel pressure regulator diaphragm. The low pressure (high vacuum) will offset the pressure being applied to the fuel pressure regulator diaphragm by the spring inside of the fuel pressure regulator. This will cause lower fuel pressure. The fuel pressure at idle will vary slightly as the barometric pressure changes, but the fuel pressure at idle should always be less than the fuel pressure noted in Step 2 with the engine turned OFF

A rich condition may result from the fuel pressure being above 325 kPa (47 psi). A rich condition can cause a DTC P0132 or a DTC P0172 to set. Driveability conditions that are associated with rich conditions can include hard starting (followed by black smoke) and a strong sulfur smell in the exhaust.

This test determines if the high fuel pressure is due to a restricted fuel return pipe or if the high fuel pressure is due to a malfunctioning fuel pressure regulator.

Fuel pressure being below 284 kPa (41 psi) can cause a lean condition. A lean condition may cause a DTC P0131 or a DTC P0171 to set. Driveability conditions that are associated with lean conditions can include hard starting (when the engine is cold), a hesitation, poor driveability, a lack of power, surging, and misfiring.

Restricting the fuel flow causes the fuel pressure to rise above the regulated fuel pressure. Using a scan tool in order to pressurize the system, the fuel pressure should rise above 325 kPa (47 psi) as the gauge outlet hose is pinched.

Check the spark plug that is associated with a particular fuel injector for fouling or saturation in order to determine if that particular fuel injector is leaking.

Fuel System Diagnosis

Step

Action

Value(s)

Yes

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

Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check

Turn OFF the ignition.
Turn OFF the air conditioning system.
Verify fuel is in the fuel tank.
Relieve the fuel pressure. Refer toFuel Pressure Relief Procedure .
Install the fuel pressure gauge, (3 on illustration).
Turn ON the ignition.

Important: To avoid false fuel pressure readings, thoroughly bleed all air out of the fuel pressure gauge.

Bleed the air out of the fuel pressure gauge into an approved gasoline container.
Turn OFF the ignition for 10 seconds.
Turn ON the ignition.

Important: The fuel pump will run for approximately 2 seconds. Cycle the ignition switch as necessary in order to achieve the highest possible fuel pressure.

Observe the fuel pressure indicated by the fuel pressure gauge with the fuel pump running.

Is the fuel pressure within the specified limits?

284-325 kPa (41-47 psi)

Go to Step 3

Go to Step 12

Important: The fuel pressure may vary slightly when the fuel pump stops running. Then, the fuel pressure should stabilize and then remain constant.

Observe the fuel pressure after the fuel pump stops running.

Does the fuel pressure drop more than the specified value in 10 minutes?

34 (5 psi)

Go to Step 10

Go to Step 4

Relieve the fuel pressure to the first specified value.
Monitor the fuel pressure.

Does the fuel pressure drop more than the second specified value in 10 minutes?

69 kPa (10 psi) 14 kPa (2 psi)

Go to Step 21

Go to Step 5

Is the fuel pressure suspected of dropping-off during acceleration, during cruise, or during hard cornering?

Go to Step 6

Go to Step 8

Visually and physically inspect the following items for a restriction:

•	The in-line fuel filter

•	The fuel feed pipe

Did you find a restriction?

Go to Step 24

Go to Step 7

Remove the modular sender assembly. Refer to Fuel Sender Assembly Replacement .
Visually and physically inspect the following items:

•	The fuel pump strainer for a restriction

•	The fuel pump flex pipe for leaks

•	Verify that the fuel pump is the correct fuel pump for this vehicle.

•	Broken baffles in the fuel tank.

•	Check the fuel pump electrical wiring for high resistance

Was a problem present in any of these areas?

Go to Step 24

Go to Step 21

Start the engine.
Observe the fuel pressure indicated by the fuel pressure gauge.

Is the fuel pressure within the specified limits?

214-303 kPa (31-44 psi)

System OK,

Go to Symptoms

Go to Step 9

Disconnect the vacuum hose from the fuel pressure regulator.
With the engine idling, apply 41-47 kPa (12-14 in. Hg) of vacuum to the fuel pressure regulator.

Is the fuel pressure within the specified limits and remain constant?

214-303 kPa (31-44 psi)

Go to Step 19

Go to Step 20

Turn OFF the ignition.
Place the bleed hose of the fuel pressure gauge into an approved gasoline container.
Turn ON the ignition.
Bleed the air out of the fuel pressure gauge.
Pressurize the fuel system with the scan tool.

Important:: Repeat pressurizing the fuel system with the scan tool as necessary to achieve the highest possible fuel pressure.

Pinch the gauge inlet hose (5).

Does the fuel pressure remain constant?

Go to Step 21

Go to Step 11

Pressurize the fuel system with the scan tool.
Wait for the fuel pressure to build.
Pinch the fuel return hose (9).

Does the fuel pressure indicated by the fuel pressure gauge remain constant?

Go to Step 20

Go to Step 22

Is the fuel pressure above the specified limit?

325 kPa (47 psi)

Go to Step 13

Go to Step 15

Relieve the fuel pressure by placing the bleed hose of the fuel pressure gauge into an approved gasoline container and by opening the relief valve.
Disconnect the fuel return hose quick-connect fitting. Refer to Quick Connect Fitting(s) Service (Metal Collar) .
Place the open end of the flexible hose into an approved gasoline container.
Turn OFF the ignition for approximately 10 seconds.
Turn ON the ignition.
Observe the fuel pressure gauge with the fuel pump running.

Is the fuel pressure within the specified limits?

284-325 kPa (41-47 psi)

Go to Step 23

Go to Step 14

Visually and physically inspect the fuel rail outlet passages for a restriction.

Was a restriction found?

Go to Step 24

Go to Step 20

Is the fuel pressure above the specified value?

0 kPa (0 psi)

Go to Step 16

Go to Step 17

Relieve the fuel pressure by placing the bleed hose of the fuel pressure gauge into an approved gasoline container and by opening the relief valve.
Pressurize the fuel system with the scan tool.
Wait for the fuel pressure to build.

Notice: Do not allow the fuel pressure to exceed the specified value because damage to the fuel pressure regulator or the fuel pressure gage may result.