System Diagnosis

1994 PCED OBDI-A

SECTION 9A: Fuel Delivery Systems

FDS: System Diagnosis

FDS1 SYSTEM INTEGRITY CHECK

Flex Fuel, DTC 141 indicates the engine ran lean an excessive period of time. Follow this procedure.

For 3.0L Taurus

Visually inspect the complete fuel delivery system, including fuel tank lines, reservoir, filter, pumps, injectors, pressure regulator, battery, electrical lines and connectors for leakage, looseness, cracks, pinching, kinking, corrosion, grounding, abrasion, or other damage caused by accident, collision, assembly or usage.
Verify vehicle has followed maintenance scheduling.
Run self-test to verify pass code. If fuel related DTCs are present, repair them first. For DTC 141, continue with this procedure.
Verify IFS switch set.
Verify that the battery is fully charged.
Check for sufficient fuel in the fuel tank.
For Type 2 fuel delivery system, repeat diagnostic procedures for both tanks.

Is system free of any evidence of leakage, damage, or any other cause for concern?

Yes	No
GO to FDS2.	SERVICE or REPLACE as required. VERIFY service.

FDS2 FUEL PRESSURE TEST

WARNING: BEFORE SERVICING OR REPLACING ANY COMPONENTS IN THE FUEL SYSTEM, REDUCE THE POSSIBILITY OF INJURY OR FIRE, AS OUTLINED UNDER "NOTES, CAUTIONS AND WARNINGS."

Key off.
Before releasing fuel system pressure at the Schrader fitting, observe the Warning Instructions to avoid fuel spillage and injury.
Install the fuel pressure tester.
Ground the fuel pump lead of the Data Link Connector (DLC) (Figure 15) with a jumper at the FP lead.
Key On, Engine Off, to operate the fuel pump(s).
Verify that the observed fuel pressure is within specified limits for the engine being checked.
Specification: Fuel System Pressure (Key On, Engine Off) Refer to "Fuel Pressure Specification Table."
On Type 2 system, perform test for both pumps.

Is fuel pressure within specification?

Yes	No
GO to FDS3.	If low:GO to FDS10. If high:GO to FDS11.

FDS3 CHECK FUEL PRESSURE LEAKDOWN

Observe the "Notes, Cautions and Warnings" to avoid fuel spillage and injury.
Connect the Fuel Pressure Test Kit at the fuel pressure test point.
Connect a jumper to the FP lead of the DLC.
Key on, engine off.
Ground the test lead using the jumper wire to run the fuel pump.
Run the fuel pump for 30 seconds minimum.
Remove the test lead ground and note fuel pressure on the gauge.
Verify whether the fuel pressure remains within the specified 5 psi for 1 minute after the test lead is ungrounded.
On dual tank system, perform test for both tanks.

Does fuel pressure remain within 5 psi for 1 minute after the test lead is ungrounded?

Yes	No
GO to FDS5.	GO to FDS4.

FDS4 CHECK PRESSURE REGULATOR DIAPHRAGM CONDITION

Key off.
Connect Fuel Pressure Test Kit at Schrader fitting on rail. Observe Warning Instructions to avoid fuel spillage and injury.
Start engine and run for 10 seconds.
Stop engine and wait 10 seconds.
Start engine and run for 10 seconds.
Stop engine and remove vacuum hose from pressure regulator.
Examine vacuum port in the pressure regulator for evidence of fuel leakage through the diaphragm.

Is vacuum port free of any fuel?

Yes	No
GO to Group 10 of the Service Manual for leak test.	REPLACE pressure regulator and RERUN test FDS2.

FDS5 CHECK FUEL PRESSURE WITH ENGINE LOAD

Fuel pressure test kit installed.
Disconnect vacuum hose at the fuel pressure regulator and plug it.
Observe fuel pressure while driving vehicle with heavy accelerations.
On Type 2 (Dual Tank System) perform test for both tanks.

Does fuel pressure reading remain within ± 3 psi during the test?

Yes	No
UNPLUG vacuum hose and connect it to fuel pressure regulator. GO to FDS6.	GO to FDS8.

FDS6 CHECK FUEL PRESSURE REGULATOR

Fuel pressure test kit installed.
Install vacuum gauge to intake manifold.
Start engine and observe both gauge readings.
Accelerate the engine speed to lower the vacuum gauge reading.

Does fuel pressure gauge reading increase as the vacuum gauge reading decreases, and/or does fuel pressure gauge reading decrease as vacuum gauge reading increases?

Yes	No
REMOVE vacuum gauge and fuel pressure test kit. GO to Section 2A for other possible causes.	GO to FDS7.

FDS7 CHECK VACUUM SUPPLY

Key off.
Vacuum hose removed from the fuel pressure regulator and plugged.
Install a hand operated vacuum pump to the fuel pressure regulator.
Start engine.
Observe fuel pressure while applying vacuum.

Does fuel pressure reading change as the vacuum changes?

Yes	No
SERVICE vacuum system. REMOVE plug from vacuum hose and RECONNECT to fuel pressure regulator.	REPLACE fuel pressure regulator.

FDS8 CHECK FUEL FILTER

Observe Warning Instructions to avoid fuel spillage and injury.
Key Off.
Install a second fuel pressure tester on Schrader valve equivalent installed between fuel pump and the in-line fuel filter, as close to fuel pump as possible.
Operate fuel pump as in FDS2 and compare pressure observed at fuel rail with the pressure observed at the fuel pump.

Is pressure at fuel pump within 5 psi of fuel rail pressure?

Note: When fuel pump is not in operation, the fuel delivery system is at the same pressure, regardless of location of pressure tap. Therefore, both gauges should read the same pressure when pump is not in operation. Any difference in pressure readings when fuel pump is not in operation is pressure gauge error.

Yes	No
For 3.0L Taurus Flex Fuel and Mark VIII: GO to FDS9. All others: GO to Group 10 of the Service Manual for additional Description, Diagnosis and Testing.	REPLACE in-line fuel filter and RECHECK pressure as in FDS2. If pressure is OK, GO to FDS3. If pressure is not OK, RECHECK fuel lines for kinks or other restrictions. SERVICE and RECHECK as in Step FDS2.

FDS9 CHECK VOLTAGE AT BOTH PUMP SPEEDS

Key off.
Connect DVOM between Inertia Fuel Shut-off (IFS) and chassis ground.
Start and run engine.
Read voltage at idle and at 3500 rpm.

Is the voltage near 9 volts at idle and near 13 volts at 3500 rpm?

Yes	No
CHECK fuel pump ground connection and service. If OK, REPLACE fuel pump.	CHECK CCRM/VCRM for proper operation. CHECK fuses of the fuel pump circuits high and low. RERUN FDS2.

FDS10 CHECK REGULATOR FOR LOW PRESSURE CAUSES

Key off.
Remove return fuel line at fuel rail and connect short hose from rail to measured container of at least one quart capacity.
Ground FP lead as in step FDS2.
Key on, engine off.
Record fuel pressure and note whether fuel is being returned to measured container. Unground FP lead after 10 seconds or if container is more than half full.

Is fuel being returned while pressure is still low?

Yes	No
REPLACE fuel pressure regulator and GO to FDS2.	For type 2: CHECK both pumps. If both are low, CHECK voltage at both pumps before replacing pumps. All others: REPLACE fuel pump assembly. GO to FDS2. Note: When replacing fuel pump, clean out tank and replace fuel filter.

FDS11 CHECK REGULATOR FOR HIGH PRESSURE CAUSES

Key off.
Remove return fuel line at fuel rail and connect short hose from rail to measured container of at least one quart capacity.
Ground FP lead as in step FDS2.
Key on, engine off.
Record fuel pressure and note whether fuel is being returned to measured container. Unground FP lead after 10 seconds or if container is more than half full.

Is fuel pressure within specification?

Yes	No
For type 2: GO to FDS12. All others: GO to FDS13.	REPLACE fuel pressure regulator and GO to FDS2.

FDS12 CHECK FUEL RETURN SYSTEM

Observe the "Notes, Cautions and Warnings" to avoid fuel spillage and injury.
Check the fuel return system(s) for restriction due to blockage, kinking, or pinching.
Remove the fuel return line at the fuel pressure regulator.
Apply 3-5 psi regulated shop air to the fuel return line.

Do you hear air entering either tank?

Yes	No
REPLACE in-tank unit where air is entering. RECONNECT fuel return line. GO to FDS2.	GO to FDS13.

FDS13 CHECK FUEL RETURN SYSTEM

Key off.
Observe the "Cautions and Warnings" to avoid fuel spillage and injury.
Fuel return line disconnected at the fuel pressure regulator.
Check the fuel return system(s) for restriction due to blockage, kinking, or pinching.
Disconnect the fuel return line near the fuel tank.
Apply 3-5 psi regulated shop air to the return line at the pressure regulator side.
On Type 2 system block return line at fuel tank on one tank and test through remaining line. Perform test for both tanks.

Does air flow freely through the line?

Yes	No
For Type 2: GO to Group 10 of the Service Manual for Description, Diagnosis and Testing of the FDM System. For Type 1: REPLACE fuel pump assembly. GO to FDS2.	SERVICE the fuel return line. RECONNECT fuel line. GO to FDS2.

FDS14 CHECK FUEL INJECTOR FLOW AND LEAKAGE

Observe "Caution and Warning" to avoid fuel spillage and injury.
Verify that the fuel injectors flow within specification, using Rotunda Injector Tester 113-00001, SBDS Injector Flow Tester or equivalent.

Is flow rate for individual injectors within specification?

Yes	No
CHECK fuel lines for leaks. GO to Group 10 of the Service Manual, then REPEAT Pinpoint Test Step FDS2.	REPLACE the defective injectors as required. RERUN test FDS14. REPEAT FDS3.

FDS15 CHECK PUMP NOISE

Fuel Pump Noise on 3.0L Taurus Flex Fuel

Conditions that can produce noise are low Methanol fuel blends (less than 30%), high fuel volatility, low fuel level (quarter fill or less), and temperature greater than 75°F. Fuel system noise may become objectionable at start-up or at high engine speed if any of the conditions are present and are considered normal. The noise level can be reduced by taking corrective action. If the noise problem cannot be corrected following this procedure, refer to Group 10 of the Service Manual.

Key off.
Observe the "Cautions and Warnings" to avoid fuel spillage and injury.
Drain fuel tank to less than a quarter tank, then fill tank to at least half with M85 fuel (15% gasoline, 85% methanol).
Start engine and check for excessive fuel pump noise.

Was pump noise reduced by adding M85 fuel?

Yes	No
ADVISE customer accordingly.	GO to FDS16.

FDS16 CHECK PUMP SPEEDS

Key off.
Connect DVOM into Inertia Fuel Shutoff (IFS) switch connector.
Start engine and monitor voltage at the IFS.

Is voltage between 12 and 14 volts during crank and initial idle speed, then drops between 7 and 10 volts after a short time?

Yes	No
GO to FDS17.	Dual voltage system may be damaged. PERFORM Quick Test and repair DTC codes.

FDS17 CHECK PRESSURE DIFFERENCE

Key off.
Observe the "Cautions and Warnings" to avoid fuel spillage and injury.
Install fuel pressure test kit.
Install a second fuel pressure tester on Schrader valve equivalent between fuel pump and the in-line fuel filter, as close to the pump as possible.
Disconnect and plug vacuum hose from fuel pressure regulator.
Start engine and observe fuel pressure difference between gauges.
Key off, compare gauge readings within 10 seconds. Both should read the same, or else one gauge is in error.

Is fuel pressure difference between gauges less than 10 psi?

Yes	No
REPLACE fuel pump assembly. INSPECT inside of tank for interference, contamination of fuel. SERVICE as necessary. REPLACE fuel filter. FILL tank with fresh fuel.	REPLACE fuel filter and CHECK system per Group 10 of the Service Manual.