DEFINITION:
Engine cranks well but does not start for a long time. Engine does eventually start, but may or may not continue to run.

Perform careful visual and physical check as described at the beginning of Section "B".
Perform "Diagnostic Circuit Check."

• CHECK
  • Fuel for poor quality, "stale" fuel, and water contamination
  • Ignition wires for shorts or faulty insulation
  • Ignition coil connections
  • Fuel pump relay. Connect test light between pump "test" terminal and BATT +. Light should be "OFF" for 2 seconds following ignition "ON." If not, use CHART A-5.
  • Secondary ignition voltage output with J 26792 (ST-125) tester or equivalent.
  • Spark plugs. Look for wear, wetness, cracks, improper gap, burned electrodes, and heavy deposits. Visually inspect ignition system for moisture, dust, cracks, burns, etc.
  • For faulty ECM and ignition grounds
  • PROM for correct application. (Consult Service Bulletins.) Spray plug wires with fine water mist to check for shorts.
  • For possibility of misfiring, crossfiring, or cutting out under load or at idle.
  • For improper crank sensor resistance or faulty connections
  • EGR operation. Use Code 32 chart.
  • Idle Air Control system. Use Code 35 chart.
  • Fuel system for restricted filter or improper pressure. Use CHART A-7.
  • Injectors for leakage. Pressurize system by energizing fuel pump through the under-hood fuel pump test connector.
  • Coolant sensor for a shift in calibration. Use Code 14 or Code 15 chart.
  • Worn dist. shaft
  • Moisture in dist. cap
  • TPS for sticking or binding. TPS voltage should read less than 1.25 volts on a "Scan" tool.
  • In-tank fuel pump check valve. A faulty valve would allow the fuel in the lines to drain back to the tank after the engine is stopped. To check for this condition, conduct the following test.
    1. Ignition "OFF."
    2. Disconnect fuel line at the filter.
    3. Remove the tank filler cap.
    4. Connect a radiator test pump to the line and apply 103 kPa (15 psi) pressure. If the pressure will hold for 60 seconds, the check valve is OK.

  • For the possibility of an exhaust restriction or improper valve timing by performing the following test.
    1. With engine at normal operating temperature, connect a vacuum gauge to any convenient vacuum port on intake manifold.
    2. Run engine at 1000 rpm and record vacuum reading.
    3. Increase engine speed slowly to 2500 rpm. Note vacuum reading at steady 2500 rpm.
    4. If vacuum at 2500 rpm decreases more than 3" Hg from reading at 1000 rpm, the exhaust system should be inspected for restrictions.
    5. Disconnect exhaust pipe from engine and repeat Steps 3 & 4. If vacuum still drops more than 3" Hg with exhaust disconnected, check valve timing. Refer to 4.3 LITER V6 (SEC. 6A3) in the 1991 Light Truck S/T Models Service Manual.

  • Engine valve timing and compression.