Test Ad: No Start - Alt Fuel Switch Indicator Is On Steady: 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) Monitor MAP & RPM PIDs
Turn ignition off. Connect scan tool to Data Link Connector (DLC). Place ALT fuel switch in GAS position. Turn ignition on. With ignition on and engine off, MAP PID should read about 14 psi and RPM PID should read zero. Using scan tool, access AFCM and select MAP and RPM PIDs from PID/DATA MONITOR & RECORD menu. Start engine and allow to idle. If MAP PID value drops with engine running and RPM PID value reads actual engine speed, go to step 5). If MAP PID drops with engine running and RPM PID does not read actual engine speed, go to next step. If MAP PID does not drop with engine running and RPM PID reads actual engine speed, go to step 4).

2) Check Tach Circuits For Opens

Turn ignition off. Disconnect bi-fuel relay module power supply harness connector C495. Disconnect in-line 42-pin connector C133. Disconnect in-line 10-pin connector C421. Using DVOM, measure resistance of Dark Blue wire between in-line harness connector C133M terminal No. 28 and in-line harness connector C421F terminal "H", and chassis ground. Also, measure resistance of Gray wire between in-line harness connector C133M terminal No. 22 and in-line harness connector C421F terminal "J", and chassis ground. See Figure and Figure . If resistances are less than 5 ohms between harness connectors C133 and C421 and more than 10 k/ohms between harness connector C421 and chassis ground, go to next step. If any resistance is 5 ohms or more between harness connectors C133 and C421 or 10 k/ohms or less between harness connector C421 and chassis ground, repair open or short to ground in affected circuit. See WIRING DIAGRAMS article.

3) Check Compuvalve Harness
Disconnect bi-fuel relay module power supply harness connector C495. Disconnect compuvalve harness connector C1294. Ensure in-line harness connector C421 is disconnected. Using DVOM, measure resistance of White wire between compuvalve harness connector C1294 terminal No. 34 and in-line harness connector C421M terminal "H". Also measure resistance of White wire between compuvalve harness connector C1294 terminal No. 38 and in-line harness connector C421M terminal "J". See Figure and Figure . If resistances are less than 5 ohms, perform COMPUVALVE CHECK under QUICK TEST. If no-start fault still exists, replace compuvalve. If either resistance measurement is 5 ohms or more, repair open in affected circuit. See WIRING DIAGRAMS article.

NOTE: Restrictor in MAP line is a calibrated length. DO NOT change length of restrictor if repairs to MAP line are necessary.

4) Check MAP Sensor Operation
Disconnect MAP line from compuvalve. Connect hand-held vacuum pump to MAP inlet on compuvalve. Place ALT fuel switch in GAS position. Turn ignition on. Using scan tool, access AFCM MAP PID from PID/DATA MONITOR & RECORD menu. Start engine and allow to idle. Record MAP PID value. Apply vacuum to MAP sensor inlet on compuvalve. Record MAP PID value. If MAP PID value reads about 14 psi before applying vacuum and value changes after applying vacuum to compuvalve, check for blockage or leaks in MAP line assembly. Repair or replace MAP line assembly as necessary. If MAP PID value reads about 14 psi before applying vacuum and value does not change after applying vacuum to compuvalve, perform COMPUVALVE CHECK under QUICK TEST. If no-start fault still exists, replace compuvalve.

5) Check Compuvalve Outlet Line For Blockage

Turn ignition off. Release ALT fuel system pressure. See FUEL SYSTEM PRESSURE RELEASE in REMOVAL, OVERHAUL & INSTALLATION - F150 PICKUP - BI-FUEL article. Disconnect compuvalve outlet line. Apply a regulated amount of air pressure to compuvalve outlet line. Have an assistant listen for air escaping from exhaust tailpipe. If air is heard escaping from exhaust tailpipe, go to next step. If no air is heard escaping from exhaust tailpipe, replace compuvalve outlet line/tuning "T". See FUEL RAILS & INJECTORS under FUEL SYSTEM in REMOVAL, OVERHAUL & INSTALLATION - F150 PICKUP - BI-FUEL article.

6) Check Injector Power Supply

Turn ignition off. Disconnect high flow injector assembly connector C1297 and low flow injector assembly connector C1289. Turn ignition on. Using DVOM, measure voltage between chassis ground and harness connector C1297M terminals "G" and "H". Also, measure voltage between chassis ground and harness connector C1289M terminal "D". See Figure and Figure . If both voltages are more than 10 volts, go to step 8). If either voltage is 10 volts or less, go to next step.

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

7) Check Injector Power Circuits From Bi-Fuel Relay Module
Turn ignition off. Disconnect bi-fuel relay module power supply harness connector C495. Disconnect bi-fuel relay module harness connector C410. Disconnect compuvalve harness connector C1294. Reconnect bi-fuel relay module power supply harness connector C495. Connect a 5-amp fused jumper wire between chassis ground and bi-fuel relay module harness connector C410F terminal "A". Turn ignition on. Using DVOM, measure voltage between chassis ground and bi-fuel relay module harness connector C410F terminal "F", "G" and "H". See Figure. If voltage is more than 10 volts, repair or replace compuvalve main harness. See WIRING DIAGRAMS article. If voltage is 10 volts or less, replace bi-fuel relay module.

8) Check Injector Circuits

Turn ignition off. Disconnect bi-fuel relay module power supply harness connector C495. Disconnect compuvalve connector C1294. Ensure in-line harness connector C1297 is disconnected. Inspect injector circuits for physical damage. If damaged, repair as necessary. If no damage exists, go to next step.

9) Check Main Harness Injector Circuits For Open

Turn ignition off. Ensure compuvalve harness connector C1294, low flow injector assembly connector C1289 and high flow injector assembly connector C1297 are disconnected. Using DVOM, measure resistance between specified connector terminals. See MAIN HARNESS INJECTOR CIRCUIT CHECK table. See Figure, Figure and Figure . If all resistances are less than 5 ohms between specified injector assembly connector and compuvalve harness connector, go to next step. If any resistance is 5 ohms or more between specified injector assembly connector and compuvalve harness connector, repair open in affected circuit. See WIRING DIAGRAMS article.

MAIN HARNESS INJECTOR CIRCUIT CHECK

Measure Between Injector Assembly Harness Connector No. & Terminal No.

Compuvalve Harness Connector No. C1294F Terminal No.

C1289F ⁽¹⁾

"A"

"B"

C1297F ⁽²⁾

"A"

"B"

"C"

"D"

"E"

"F" ⁽³⁾

⁽¹⁾	See Figure.

⁽²⁾	See Figure.

⁽³⁾

LPG only.

10) Check Main Harness Injector Circuits For Short To Ground

Using DVOM, measure resistance between chassis ground and low flow injector assembly connector C1289 terminals "A" and "B". Also, measure resistance between chassis ground and high flow injector assembly connector C1297 terminals "A", "B", "C", "D", "E" and "F". See Figure, Figure and Figure . If all resistances are more than 10 k/ohms between compuvalve harness connector and chassis ground, perform COMPUVALVE CHECK under QUICK TEST. If no-start fault still exists, replace compuvalve. If any resistance is 10 k/ohms or less between compuvalve harness connector and chassis ground, repair short to ground in affected circuit. See WIRING DIAGRAMS article.