Diagnostic Aids

Enter this test only when all steps under QUICK TEST have been successfully completed and engine still does not start or if directed here from another test or chart. This test is only intended to diagnose:

• Fuel pump intercept.
• Bi-fuel relay module.
• Harness circuits.

1. 1) Bypass Fuel Pump Intercept
   
   Turn ignition switch to OFF position. Disconnect fuel pump intercept connectors (C4420 and C732 on Contour, C4302 and C415 on F150, or C4302 and C1045 on F350 Super Duty). Ensure base gasoline fuel pump harness is connected to fuel pump and sender. Place ALT fuel switch in GAS position. Start engine. If engine starts with ALT fuel switch in GAS position, go to next step. If engine does not start with ALT fuel switch in GAS position, see NO START/NORMAL CRANK (GASOLINE) under SYMPTOMS in TROUBLESHOOTING - NO CODES - EEC-V (BI-FUEL) article.
2. 2) Check Bi-Fuel Relay Operation
   
   Turn ignition switch to OFF position. Disconnect bi-fuel relay module connectors C4019, C4026 and C4035. See Figure-Figure . Check continuity between bi-fuel relay module harness connector C4019 terminals No. 1 and 2. If continuity exists, go to next step. If continuity does not exist, replace bi-fuel relay module.
3. 3) Check Fuel Pump Intercept Harness
   
   Ensure ignition switch is turned to OFF position. Connect a jumper wire between bi-fuel relay module harness connector C4019 terminals No. 1 and 2. Ensure ALT fuel switch is in GAS position. Start engine. If engine starts with ALT fuel switch in GAS position, go to next step. If engine does not start with ALT fuel switch in GAS position, repair or replace fuel pump intercept harness between bi-fuel relay module and fuel tank unit.
4. 4) Check Bi-fuel Relay Module
   
   Ensure ignition switch is turned to OFF position. Reconnect bi-fuel relay module connectors C4026 and C4035. Leave bi-fuel relay module connector C4019 disconnected. Ensure ALT fuel switch is in GAS position. Turn ignition switch to ON position. Measure resistance between bi-fuel relay module connector C4019 terminals No. 1 and 2. If resistance is 5 ohms or more, go to next step. If resistance is less than 5 ohms, reconnect all connectors and restart vehicle. If no-start fault is still present, go to next step.
5. 5) Check Compuvalve
   
   Turn ignition switch to OFF position. Ensure ALT fuel switch is in GAS position. Turn ignition switch to ON position. Measure voltage between bi-fuel relay module connector C4016 terminals No. 1 and 2. See Figure. If voltage is not present, replace bi-fuel relay module. If voltage is present, check for short to ground between compuvalve C4025 terminal No. 5 and bi-fuel relay module C4016 terminal No. 1. See Figure. If no shorts to ground are present and fault still exists, replace compuvalve.