Fuel System Diagnosis
Diagnostic Instructions
Circuit/System Description
The engine control module (ECM) supplies a high voltage signal
to the fuel pump flow control module when the ECM detects that the
ignition is ON. The high voltage signal from the ECM to the fuel
pump flow control module remains active for 2 s, unless the engine
is in Crank or Run. While this signal is being received, the fuel
pump flow control module closes the ground switch of the fuel pump
and also supplies a varying voltage to the fuel tank fuel pump
module in order to maintain the desired fuel rail pressure. The
fuel system is an electronic returnless on-demand design. A
returnless fuel system reduces the internal temperature of the fuel
tank by not returning hot fuel from the engine to the fuel tank.
Reducing the internal temperature of the fuel tank results in lower
evaporative emissions. The fuel tank stores the fuel supply. An
electric turbine style fuel pump attaches to the fuel tank module
inside the fuel tank. The fuel pump supplies high pressure fuel
through the fuel filter, contained in the fuel tank module, and the
fuel feed pipe to the fuel injection system. The fuel pump provides
fuel at a higher rate of flow than is needed by the fuel injection
system. The fuel pump also supplies fuel to a venturi pump located
on the bottom of the fuel tank module. The function of the venturi
pump is to fill the fuel tank module reservoir. The fuel tank
module contains a reverse flow check valve. The check valve
maintains fuel pressure in the fuel feed pipe and the fuel rail in
order to prevent long cranking times.
Reference Information
Description and Operation
Fuel System Description
Electrical Information Reference
Scan Tool Reference
Control Module References for scan tool information
Special Tools
| • |
CH 48027
Digital Pressure Gauge |
| • |
EN 37287 Fuel
Line Shut-Off Adapters |
For equivalent regional tools, refer to
Special Tools .
Circuit/System Verification
Note:
| • |
Repair all fuel
system related DTCs before performing this diagnostic, unless
instructed here from a DTC diagnostic. |
| • |
Inspect the fuel
system for damage or external leaks before proceeding. |
| • |
Verify that an
adequate amount of fuel is in the fuel tank before
proceeding. |
| • |
Before proceeding
with this test review the User Manual of the CH 48027
Digital Pressure Gauge chapter 5 for Safety Information and
Instructions. |
| • |
Do not perform the
Fuel System Diagnosis if the engine coolant temperature (ECT) is
above 60°C (150°F). High fuel pressure readings may result
due to hot soak fuel boiling. With the engine OFF, the fuel
pressure may increase to the setting of the pressure relief
regulator valve, 580 kPa (84 PSI). |
| 2. |
Ignition ON, engine OFF,
command the fuel pump ON with a scan tool. Verify the fuel pressure
is between 345-414 kPa (50-60 PSI) and does not decrease greater
than 34 kPa (5 PSI) in 1 min. |
Circuit/System Testing
|
Note:
| • |
The fuel pump may
need to be commanded ON a few times in order to obtain the highest
possible fuel pressure. |
| • |
Do not start the
engine. |
|
| 1. |
Ignition ON, engine OFF,
command the fuel pump ON with a scan tool and observe the fuel
pressure gauge while the G12 Fuel Pump is operating. Verify the
fuel pressure is between 345-414 kPa (50-60 PSI). |
| ⇒ |
If the fuel pressure is less than the specified
range, test, inspect, and repair the items listed below. If all
items test normal, replace the G12 Fuel Pump. |
| |
• |
Restricted fuel feed
pipe |
| |
• |
Restricted or clogged
strainer |
| |
• |
Restricted or plugged fuel
filter |
| |
• |
Inspect the G12 Fuel Pump
harness connectors and the ground circuits of the fuel pump for
poor connections. |
|
Note: The fuel
pressure may vary slightly when the G12 Fuel Pump stops operating.
After the G12 Fuel Pump stops operating, the fuel pressure should
stabilize and remain constant.
|
| 2. |
Verify the fuel pressure does
not decrease greater than 34 kPa (5 PSI) in 1 min. |
| ⇒ |
If the fuel pressure decreases more than the
specified value, perform the following procedure: |
| |
2.1 |
Ignition OFF, relieve fuel
pressure. |
| |
2.2 |
Install the EN 37287
Fuel Line Shut-Off Adaptors between the fuel feed pipe and
the fuel rail. |
| |
2.3 |
Open the valve on the EN
37287 Fuel Line Shut-Off Adaptors . |
| |
2.4 |
Ignition ON, command the fuel
pump ON with a scan tool and bleed the air from the digital
pressure gauge. |
| |
2.5 |
Close the valve on the EN
37287 Fuel Line Shut-Off Adaptors . |
| |
2.6 |
Command the fuel pump ON with
a scan tool. |
| |
2.7 |
Verify the fuel pressure does
not decrease greater than 34 kPa (5 PSI) in 1 min. |
| ⇒ |
If the fuel pressure decreases more than 34 kPa (5 PSI) within
the specified time, locate and replace the leaking fuel
injector(s). If the fuel pressure does not decrease more than 34
kPa (5 PSI) within the specified time, replace the G12 Fuel
Pump. |
| 3. |
Relieve the fuel pressure to
69 kPa (10 PSI). Verify that the fuel pressure does not decrease
more than 14 kPa (2 PSI) in 5 min. |
| ⇒ |
If the fuel pressure decreases more than the
specified value, replace the G12 Fuel Pump. |
| 4. |
Remove the EN 37287
Fuel Line Shut-Off Adaptors and CH 48027
Digital Pressure Gauge . |
| 5. |
Operate the vehicle within the
conditions of the customers concern while monitoring fuel related
parameters with a scan tool. The scan tool parameters should not
indicate a lean condition. |
| ⇒ |
If the scan tool parameters indicate a lean
condition, test for a restricted fuel feed pipe, restricted fuel
filter, or poor connections at the harness connectors and ground
circuits of the fuel pump. If all test normal, replace the fuel
pump. |
Repair Instructions
Perform the
Diagnostic Repair Verification after completing the diagnostic
procedure.
Fuel Tank Fuel Pump Module Replacement
|
