GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Isuzu 🢒 2007 🢒 Isuzu MD F-Series 🢒 Engine 🢒 Engine Electrical 🢒 Engine Cranks But Does Not Run

Diagnostic Instructions
    • Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
    • Review Strategy Based Diagnosis for an overview of the diagnostic approach.
    •  Diagnostic Procedure Instructions provides an overview of each diagnostic category.

Circuit/System Description

The Engine Cranks but Does Not Run diagnostic table is an organized approach to identifying a condition that causes an engine not to start. The Engine Cranks but Does Not Run diagnostic table directs the service technician to the appropriate system diagnosis.

Diagnostic Aids

If the cause of an engine cranks but will not run condition has not been found, inspect for the following conditions:

    • Hard starting only in cold ambient temperatures. These may cause an intermittent condition that may not occur in the service bay:
       - Fuel heater inoperative
       - Ice blockage at the fuel pickup in the fuel tank--This will be a high vacuum in the supply lines while cranking, and the problem will disappear after the vehicle is brought in the service bay. It may also exhibit a start and stall condition or a starting condition with no acceleration.
    • The correct cranking speed is 100 RPM cold and 180 RPM hot.
    • A basic engine problem
    • Low engine coolant may cause the engine to shut down.

Reference Information

Schematic Reference

Engine Controls Schematics

Connector End View Reference

    •  Engine Controls Component Views
    •  Engine Control Module Connector End Views

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

    •  Scan Tool Data List
    •  Scan Tool Data Definitions

Circuit/System Verification

Important: This diagnostic assumes the following:

   • The batteries are completely charged. Refer to Battery Inspection/Test.
   • The cranking speed is within specifications. Refer to Engine Cranks Slowly.
   • There is adequate fuel in the fuel tanks.

  1. If any DTCs are set diagnose those DTCs first.
  2. The engine starts and runs.
    3. ⇒If the engine does not start and run perform the Circuit/System Testing.

Circuit/System Testing

Important: You must perform the Circuit/System Verification before proceeding with Circuit/System Testing.

  1. Turn OFF the ignition for 1 minute, then crank over the engine for 15 seconds. Monitor the DTCs with a scan tool. If DTCs are set, diagnose those DTCs first.
  2. Inspect for the following conditions:
    3. • Fuel smell or leak
    • Air in the fuel lines after running out of fuel--Refer to Fuel System Bleeding.
    • A plugged air filter or collapsed air intake duct
    • A restricted exhaust system--Refer to Symptoms - Engine Exhaust.
    • Contaminants in fuel--Refer to Contaminants-in-Fuel Diagnosis.
  3. Observe the actual fuel rail pressure parameter with a scan tool. The value should be 0 MPa with the ignition ON, engine OFF.
    4. ⇒If the pressure difference between the actual and desired pressure are more than 2 MPa, replace the fuel pressure sensor.
  4. Observe the Actual Fuel Rail Pressure parameter with a scan tool with the ignition ON and engine OFF. Wait 1 minute. The value should be 0 MPa with the ignition ON, engine OFF. If the actual fuel rail pressure is more than 2 MPa, replace the fuel rail pressure sensor.
  5. Observe the Actual Fuel Rail Pressure AND Desired Fuel Rail Pressure parameters with a scan tool while cranking the engine. The parameters should be within 2 MPa of each other.
    6. ⇒ If the pressure difference between the actual and desired pressure are more than 2 MPa , inspect for a fuel filter restriction, air being introduced into the fuel lines from the tank to the fuel supply pump or kinked fuel lines.
    ⇒If there is no condition from the fuel tank to the fuel supply pump, replace the fuel injection supply pump.
  6. Inspect for nominal readings at key-up or cranking, where denoted, for the following parameters. Use the Engine Control Module Scan Tool Information, LF8, list or a known good vehicle to determine nominal values.
    7. • Camshaft and crankshaft signal present, during crank
    • Barometric pressure, at key-up
    • Engine coolant temperature, at key-up
    • Turbocharger boost pressure, at key-up
      Diagnose and repair sensors or sensor circuits, as necessary.
  7. Other possible causes for a no-start condition:
    8. • Heavily restricted exhaust, plugged exhaust filter or catalytic converter
    • Poor engine compression
    • Water or gasoline in fuel system
    • Engine mechanical timing
    • Flywheel incorrectly installed or too much crankshaft end-play causing No Crankshaft Present signal on the scan tool
      Diagnose and repair, as necessary. If everything tests OK, replace the ECM.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Fuel Pressure Sensor Replacement
    •  Fuel Pressure Regulator Replacement
    •  Control Module References for ECM replacement, setup, and programming