Ford F150 Pickup. Instruction - part 1350

RELEASE under FUEL SYSTEMS in REMOVAL & INSTALLATION - F150 PICKUP - CNG article. 
Close instruction lock-down valve jackscrew on forward in-bed fuel tank and mid fuel tank (if equipped) 
solenoid valve. See Fig. 10. Tighten jackscrew(s) to 62-79 INCH lbs. (7-9 N.m). Open manual backflow 
valve on fuel filler valve. Open manual bleed valve on fuel filler neck venting kit for 60 seconds, then 
close bleed valve. Observe and record system pressure on fuel filler neck venting kit pressure gauge. If 
pressure is zero psi (zero kPa), go to step 3. If pressure is more than zero psi (zero kPa), go to next step. 

2. Check Rear In-Bed Fuel Tank Solenoid Valve Power Circuit For Short To Voltage 

 
Ensure ignition is off. Disconnect rear in-bed fuel tank solenoid valve harness connector C4123. Using 
DVOM, measure voltage between chassis ground and rear in-bed fuel tank solenoid valve harness 
connector C4123 terminal No. 1 (Pink/Black wire). See Fig. 6. If voltage is more than 10 volts, repair 
short to power in Pink/Black wire. See ENGINE PERFORMANCE in appropriate SYSTEM WIRING 
DIAGRAMS article in ELECTRICAL. Retest system for normal operation and go to step 

6

. If voltage is 

10 volts or less, mark rear in-bed fuel tank solenoid valve as "Stuck Open". A NEW solenoid valve will 
be installed after diagnostics are completed. Go to step 6. 

3. Check Rear In-Bed Fuel Tank Solenoid Valve Operation 

Turn ignition off. Reconnect rear in-bed fuel tank solenoid valve harness connector C4123. Connect scan 
tool to Data Link Connector (DLC). Turn ignition on. Using scan tool, enter OUTPUT TEST MODE. 
Press "Start" button on scan tool to command all outputs on. Observe and record pressure on fuel filler 
neck venting kit pressure gauge. Press "Stop" button on scan tool. If pressure reading was zero psi (zero 
kPa) when "Start" button was pressed, go to next step. If pressure reading was more than zero psi (zero 
kPa) when "Start" button was pressed, mark rear in-bed fuel tank solenoid valve as "Functions Normally", 
then go to step 6. 

4. Check Rear In-Bed Fuel Tank Solenoid Valve Power Circuit For An Open 

Turn ignition off. Disconnect rear in-bed fuel tank solenoid valve harness connector C4123. Turn ignition 
on. Using scan tool, enter OUTPUT TEST MODE. Press "Start" button on scan tool to command all 
outputs on. Using DVOM, measure voltage between chassis ground and rear in-bed fuel tank solenoid 
valve harness connector C4123 terminal No. 1 (Pink/Black wire). See Fig. 6. If voltage is more than 10 
volts, go to next step. If voltage is 10 volts or less, repair open in Pink/Black wire. See ENGINE 
PERFORMANCE in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL. Retest 
system for normal operation and go to step 6. 

5. Check Rear In-Bed Fuel Tank Solenoid Valve Ground Circuit For An Open 

 
Turn ignition off. Using DVOM, measure resistance between chassis ground and rear in-bed fuel tank 
solenoid valve wiring harness connector C4123 terminal No. 2 (Black wire). If resistance is less than 5 

NOTE:

This procedure will supply power to fuel tank solenoid valve for 
approximately 30-60 seconds. If time expires, cycle "Start/Stop" button on 
scan tool to restore power.

NOTE:

This procedure will supply power to fuel tank solenoid valve for 
approximately 30-60 seconds. If time expires, cycle "Start/Stop" button on 
scan tool to restore power.

 

2003 Ford Pickup F150 

2003 ENGINE PERFORMANCE System & Component Testing - CNG

  

ohms, mark rear in-bed fuel tank solenoid valve as "Stuck Closed". A NEW solenoid valve will be 
installed after diagnostics are completed. Go to next step. If resistance is 5 ohms or more, repair open in 
Black wire between chassis ground and solenoid valve. See ENGINE PERFORMANCE in appropriate 
SYSTEM WIRING DIAGRAMS article in ELECTRICAL. Retest system for normal operation and go to 
next step. 

6. Check Forward In-Bed Fuel Tank Solenoid Valve For An Open 

 
Turn ignition off. Reconnect rear in-bed fuel tank solenoid valve harness connector C4123. Close instruction 
lock-down valve jackscrew on rear in-bed fuel tank solenoid valve. See Fig. 10. Tighten jackscrew to 62-
79 INCH lbs. (7-9 N.m). See Fig. 9. Open manual lock-down jackscrew on forward in-bed fuel tank 
solenoid valve. Open manual bleed valve on fuel filler neck venting kit for 60 seconds, then close bleed 
valve. Observe and record system pressure on fuel filler neck venting kit pressure gauge. If pressure is 
zero psi (zero kPa), go to step 8. If pressure is more than zero psi (zero kPa), go to next step. 

7. Check Forward In-Bed Fuel Tank Solenoid Valve Power Circuit For Short To Voltage 

 
Ensure ignition is off. Disconnect forward in-bed fuel tank solenoid valve harness connector C4124. 
Using DVOM, measure voltage between chassis ground and forward in-bed fuel tank solenoid valve 
harness connector C4124 terminal No. 1 (Pink/Black wire). See Fig. 6. Proceed as follows: 

z

If voltage is 10 volts or more and vehicle is not equipped with a midship fuel tank, repair short to 
voltage in Pink/Black wire. See ENGINE PERFORMANCE in appropriate SYSTEM WIRING 
DIAGRAMS article in ELECTRICAL. Replace solenoids marked "Stuck Open" or "Stuck Closed" 
and retest system for normal operation.  

z

If voltage is 10 volts or more and vehicle is equipped with a midship fuel tank, repair short to 
voltage in Pink/Black wire and go to step 11. See ENGINE PERFORMANCE in appropriate 
SYSTEM WIRING DIAGRAMS article in ELECTRICAL.  

z

If voltage is less than 10 volts and vehicle is not equipped with a midship fuel tank, replace forward 
in-bed fuel tank solenoid valve and all other solenoids marked "Stuck Open" or "Stuck Closed". 
Retest system for normal operation.  

z

If voltage is less than 10 volts and vehicle is equipped with a midship fuel tank, mark forward in-
bed fuel tank solenoid valve as "Stuck Open" and go to step 11.  

8. Check Forward In-Bed Fuel Tank Solenoid Valve Operation 

Ensure ignition is off. Reconnect forward in-bed fuel tank solenoid valve harness connector C4124. Turn 
ignition on. Using scan tool, enter OUTPUT TEST MODE. Press "Start" button on scan tool to command 
all outputs on. Observe and record pressure on fuel filler neck venting kit pressure gauge. Press "Stop" 
button on scan tool. If pressure is zero psi (zero kPa) when "Start" button is pressed, go to next step. If 
pressure is not zero psi (zero kPa) when "Start" button is pressed, mark forward in-bed fuel tank solenoid 
valve as "Functions Normally". If vehicle is equipped with a midship fuel tank, go to step 11. If vehicle is 
not equipped with a midship fuel tank, replace any solenoid valve that is marked "Stuck Closed" or 
"Stuck Open". Retest system for normal operation. 

NOTE:

This procedure will supply power to fuel tank solenoid valve for 
approximately 30-60 seconds. If time expires, cycle "Start/Stop" button on 
scan tool to restore power.

 

2003 Ford Pickup F150 

2003 ENGINE PERFORMANCE System & Component Testing - CNG

  

9. Check Forward In-Bed Fuel Tank Solenoid Valve Power Circuit For An Open 

Turn ignition off. Disconnect forward in-bed fuel tank solenoid valve harness connector C4124. Turn 
ignition on. Using scan tool, enter OUTPUT TEST MODE. Press "Start" button on scan tool to command 
all outputs on. Using DVOM, measure voltage between chassis ground and forward in-bed fuel tank 
solenoid valve harness connector C4124 terminal No. 1 (Pink/Black wire). See 

Fig. 6

. If voltage is more 

than 10 volts, go to next step. If voltage is 10 volts or less, repair open in Pink/Black wire. See ENGINE 
PERFORMANCE in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL. If vehicle is 
equipped with a midship fuel tank, go to step 11. If vehicle is not equipped with a midship fuel tank, 
replace any solenoid valve that is marked "Stuck Closed" or "Stuck Open". Retest system for normal 
operation. 

10. Check Forward In-Bed Fuel Tank Solenoid Valve Ground Circuit For An Open 

 
Turn ignition off. Using DVOM, measure resistance between chassis ground and forward in-bed fuel tank 
solenoid valve harness connector C4124 terminal No. 2 (Black wire). Proceed as follows: 

z

If resistance is 5 ohms or more and vehicle is not equipped with a midship fuel tank, repair open in 
Black wire and replace any solenoids marked "Stuck Open" or "Stuck Closed". See ENGINE 
PERFORMANCE in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL. 
Retest system for normal operation.  

z

If resistance is 5 ohms or more and vehicle is equipped with a midship fuel tank, repair open in 
Black wire and go to next step. See ENGINE PERFORMANCE in appropriate SYSTEM WIRING 
DIAGRAMS article in ELECTRICAL.  

z

If resistance is less than 5 ohms and vehicle is not equipped with a midship fuel tank, replace 
forward in-bed fuel tank solenoid valve and any other solenoid marked "Stuck Open" or "Stuck 
Closed". Retest system for normal operation.  

z

If resistance is less than 5 ohms and vehicle is equipped with a midship fuel tank, mark forward in-
bed fuel tank solenoid valve as "Stuck Closed" and go to next step.  

11. Check Midship Fuel Tank Solenoid Valve For An Open 

 
Ensure ignition is off. Reconnect forward in-bed fuel tank solenoid valve harness connector C4124. Close 
instruction lock-down valve jackscrews on forward and rear in-bed fuel tank solenoid valves. See Fig. 10. 
Tighten manual lock-down jackscrews 62-79 INCH lbs. (7-9 N.m). Open manual lock-down jackscrew 
on midship fuel tank solenoid valve. Open manual bleed valve on fuel filler neck venting kit for 60 
seconds, then close bleed valve. Observe and record system pressure on fuel filler neck venting kit 
pressure gauge. If pressure is zero psi (zero kPa), go to step 13. If pressure is more than zero psi (zero 
kPa), go to next step. 

12. Check Midship Fuel Tank Solenoid Valve Power Circuit For Short To Voltage 

 
Ensure ignition is off. Disconnect midship fuel tank solenoid valve harness connector C4126. Using 
DVOM, measure voltage between chassis ground and midship fuel tank solenoid valve harness connector 

NOTE:

This procedure will supply power to fuel tank solenoid valve for 
approximately 30-60 seconds. If time expires, cycle "Start/Stop" button on 
scan tool to restore power.

 

2003 Ford Pickup F150 

2003 ENGINE PERFORMANCE System & Component Testing - CNG

  

C4126 terminal No. 1 (Pink/Black wire). See Fig. 6. If voltage is more than 10 volts, repair short to 
power in Pink/Black wire. Replace any solenoid valve that is marked "Stuck Closed" or "Stuck Open" 
and retest system for normal operation. See ENGINE PERFORMANCE in appropriate SYSTEM 
WIRING DIAGRAMS article in ELECTRICAL. If voltage is 10 volts or less, replace midship fuel tank 
solenoid valve and any solenoid valve that is marked "Stuck Closed" or "Stuck Open". Retest system for 
normal operation. 

13. Check Midship Fuel Tank Solenoid Valve Operation 

Ensure ignition is off. Reconnect midship fuel tank solenoid valve harness connector C4126. Turn 
ignition on. Using scan tool, enter OUTPUT TEST MODE. Press "Start" button on scan tool to command 
all outputs on. Observe and record pressure on fuel filler neck venting kit pressure gauge. Press "Stop" 
button on scan tool. If pressure is zero psi (zero kPa) when "Start" button was pressed, go to next step. If 
pressure is more than zero psi (zero kPa) when "Start" button was pressed, mark midship fuel tank 
solenoid valve as "Functions Normally". Replace any solenoid valve that is marked "Stuck Closed" or 
"Stuck Open" and retest system for normal operation. 

14. Check Midship Fuel Tank Solenoid Valve Power Circuit For An Open 

Turn ignition off. Disconnect midship fuel tank solenoid valve harness connector C4126. Turn ignition 
on. Using scan tool, enter OUTPUT TEST MODE. Press "Start" button on scan tool to command all 
outputs on. Using DVOM, measure voltage between chassis ground and midship fuel tank solenoid valve 
harness connector C4126 terminal No. 1 (Pink/Black wire). If voltage is more than 10 volts, go to next 
step. If voltage is 10 volts or less, repair open in Pink/Black wire. See ENGINE PERFORMANCE in 
appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL. Replace any solenoid valve that 
is marked "Stuck Closed" or "Stuck Open" and retest system for normal operation. 

15. Check Midship Fuel Tank Solenoid Valve Ground Circuit For An Open 

 
Turn ignition off. Using DVOM, measure resistance between chassis ground and midship fuel tank 
harness connector C4126 terminal No. 2 (Black wire). If resistance is more than 5 ohms, repair open in 
Black wire. See ENGINE PERFORMANCE in appropriate SYSTEM WIRING DIAGRAMS article in 
ELECTRICAL. Replace any solenoid valve that is marked "Stuck Closed" or "Stuck Open" and retest 
system for normal operation. If resistance is 5 ohms or less, replace midship fuel tank solenoid valve and 
any solenoid valve that is marked "Stuck Closed" or "Stuck Open". Retest system for normal operation. 

NOTE:

This procedure will supply power to fuel tank solenoid valve for 
approximately 30-60 seconds. If time expires, cycle "Start/Stop" button on 
scan tool to restore power.

NOTE:

This procedure will supply power to fuel tank solenoid valve for 
approximately 30-60 seconds. If time expires, cycle "Start/Stop" button on 
scan tool to restore power.

 

2003 Ford Pickup F150 

2003 ENGINE PERFORMANCE System & Component Testing - CNG