Test Ab: No Start - Alt Fuel Switch Indicator Off: Testing

WARNING: This page is about a different car, the 2002 Ford Pickup and 2002 Ford Cab & Chassis. However, it is still accessible from the selected car via links, so may be relevant.

CAUTION: Always disconnect bi-fuel relay module power supply 3-pin harness connector C495 before disconnecting or reconnecting compuvalve main harness connector C1294 to avoid damaging compuvalve or connectors. See Figure.

1) Check Communication With AFCM
Connect scan tool to Data Link Connector (DLC). Turn ignition on. Using scan tool, select vehicle and engine. Select AFCM-ALTERNATE FUEL CONTROL MODULE. Access FAP, OPMODE, and SWITCH PIDS from PID/DATA MONITOR & RECORD menu. If communication with AFCM is possible go to step 8). If communication between scan tool and AFCM is not possible, go to next step.

2) Check Bi-Fuel Relay Module Fuse No. 1 (3-Amp)

Remove and inspect bi-fuel relay module fuse No. 1 (3-amp) located in bi-fuel relay module. See Figure. Bi-fuel relay module is located on left side, rear of engine compartment. If fuse is okay, go to next step. If fuse is blown, replace fuse and retest system.

3) Check Ground To Bi-Fuel Relay Module

Disconnect bi-fuel relay module harness connector C410. Using DVOM, measure resistance between chassis ground and bi-fuel relay module C410M terminal "A". If resistance is less than 5 ohms, reconnect bi-fuel relay module harness connector C410 and go to next step. If resistance is 5 ohms or more, repair open in ground circuit to bi-fuel relay module. See WIRING DIAGRAMS article.

4) Check Voltage To Bi-Fuel Relay Module

Turn ignition off. Disconnect bi-fuel relay module power supply harness connector C495. Turn ignition on. Using DVOM, measure voltage between chassis ground and bi-fuel relay module power supply harness connector C495F terminals "A" and "B". See Figure. If both voltages are more than 10 volts, go to next step. If either voltage is 10 volts or less, repair open or short in affected circuit. See WIRING DIAGRAMS article.

5) Check KAPWR Output From Bi-Fuel Relay Module

Disconnect bi-fuel relay module connector C410. Connect bi-fuel relay module power supply connector C495. Using DVOM, measure voltage between chassis ground and bi-fuel relay module C410F terminal "C". See Figure. If voltage is more than 10 volts, go to next step. If voltage is 10 volts or less, replace bi-fuel relay module.

NOTE: Bi-fuel power relay should "click" when harness connector C410F terminal "A" is grounded.

6) Check VPWR Output From Bi-Fuel Relay Module
Ensure bi-fuel relay module connector C410 is disconnected. Turn ignition on. Connect a 5-amp fused jumper wire between chassis ground and bi-fuel relay module harness connector C410F terminal "A". Using DVOM, measure voltage between chassis ground and bi-fuel relay module harness connector C410F terminals "D", "E", "F", "G", "H" and "J" (White wires). See Figure. If all voltages are more than 10 volts, go to next step. If either voltage is 10 volts or less, replace bi-fuel relay module.

CAUTION: Be very careful when probing compuvalve harness connector terminals. These terminals can be damaged if overstressed, resulting in harness replacement.

7) Check Compuvalve Main Harness
Turn ignition off. Disconnect bi-fuel relay module power supply harness connector C495. Disconnect compuvalve harness connector C1294. Ensure bi-fuel relay module connector C410 is disconnected. Using DVOM, measure resistance between chassis ground and bi-fuel relay module harness connector C410M terminal "A". Also, measure resistance between specified compuvalve harness connector terminals and bi-fuel relay module harness connector terminals. See COMPUVALVE MAIN HARNESS CONTINUITY TEST table. See Figure and Figure . If all resistances are less than 5 ohms, perform COMPUVALVE CHECK under QUICK TEST. If no-start fault still exists, replace compuvalve. If any resistance is 5 ohms or more, repair open in affected circuit. See WIRING DIAGRAMS article.

COMPUVALVE MAIN HARNESS CONTINUITY TEST

Bi-Fuel Relay Harness Connector C410M Terminal	Compuvalve Harness Connector C1294 Terminal No.
"C"	2
"B"	5
"D"	9, 11 & 13
"E"	9, 11 & 13

8) Check ALT Fuel Switch Circuit Voltage

Turn ignition off. Disconnect compuvalve 10-pin in-line harness connector C422, located in rear right side of engine compartment. Turn ignition on. Using DVOM, measure voltage between chassis ground and in-line harness connector C422M terminal "E". See Figure. If voltage is 10 volts or less, go to next step. If voltage is more than 10 volts, go to step 10).

NOTE: Bi-fuel power relay should "click" when connector C410F terminal "A" is grounded.

9) Check Power To ALT Fuel Switch
Turn ignition off. Disconnect bi-fuel relay module power supply harness connector C495. Disconnect bi-fuel relay harness connector C410. Reconnect bi-fuel relay module power supply harness connector C495. Turn ignition on.
Connect a 5-amp fused jumper wire between chassis ground and bi-fuel relay module harness connector C410F terminal "A". Using DVOM, measure voltage between chassis ground and bi-fuel relay module harness connector C410F terminals "D" and "E" (White wires). See Figure. If both voltages are more than 10 volts, replace compuvalve main harness. If either voltage is 10 volts or less, replace bi-fuel relay module.

10) Check Circuits To ALT Fuel Switch

Ensure compuvalve 10-pin in-line harness connector C422 is disconnected. Place ALT fuel switch in ALT position. Using DVOM, measure resistance between in-line harness connector C422F terminal "F" (Yellow wire) and terminal "H" (Dark Green wire). See Figure. If resistance is 5 ohms or more with switch in ALT position, go to next step. If resistance is less than 5 ohms with switch in ALT position, go to step 12).

11) Check ALT Fuel Switch Operation

Disconnect ALT fuel switch 3-pin connector C4013. Place ALT fuel switch in ALT position. Using DVOM, measure resistance between ALT fuel switch connector C4013M terminal "B" (Yellow wire) and terminal "C" (Dark Green wire). See Figure. If resistance is less than 5 ohms, repair open in affected circuit between ALT fuel switch connector C4013 and compuvalve in-line harness connector C422. If resistance is 5 ohms or more, check for open in Yellow or Dark Green wires between ALT fuel switch connector C4013 and ALT fuel switch. See WIRING DIAGRAMS article. Repair as necessary. If circuits are okay, replace ALT fuel switch.

CAUTION: Be very careful when probing compuvalve harness connector terminals. These terminals can be damaged if overstressed, resulting in harness replacement.

12) Check Circuit Between ALT Fuel Switch & Compuvalve
Turn ignition off. Disconnect bi-fuel relay module power supply harness connector C495. Disconnect compuvalve harness connector C1294. Using DVOM, measure resistance of White wire between compuvalve harness connector C422M terminal "F" and compuvalve harness connector C1294 terminal No. 46. See Figure and Figure . If resistance is less than 5 ohms, perform COMPUVALVE CHECK under QUICK TEST. If no-start fault still exists, replace compuvalve. If resistance is 5 ohms or more, repair open in White wire between compuvalve harness connector C422 and compuvalve harness connector C1294. See WIRING DIAGRAMS article.