GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 1998 🢒 GMC P42 Commercial Chassis 🢒 Engine 🢒 Engine Controls - 6.5L (L57) 🢒 Hard Start

Hard Start EFI

Checks

Action

Definition: The engine cranks OK, but does not start for a long time. The engine does eventually run, or may start but immediately dies.

Preliminary Checks
    • Refer to Symptoms .
    • Make sure the driver is using the correct starting procedure.

Sensor Checks

Check the Engine Coolant Temperature (ECT) sensor. Use the Scan Tool in order to compare the engine coolant temperature with the ambient air temperature on a cold engine. If the coolant temperature reading is more than 5° greater or less than the ambient air temperature on a cold engine, check for a high resistance in the coolant sensor circuit or the sensor itself.

Fuel System Checks
    • Check the supply to the injection pump. Refer to Fuel Supply System Check .
    • Check for air in the fuel system. Refer to Fuel Supply System Check .
    • Check the fuel return from the injection pump. Refer to Fuel Return System Diagnosis .
    • Check the engine shut-off solenoid operation.
    • Check the fuel injection nozzles. Refer to Injection Nozzle(s) Diagnosis .
    • Check the fuel tank cap vent.
    • Check for an internal injection pump problem. Refer to Fuel Injection System Diagnosis .

Electrical System Checks
    • Check the glow plug operation. Refer to Glow Plug System Check .
    • Check for slow cranking speed.

Air Intake System Checks
    • Check the air cleaner and the air intake ducts for a restriction.
    • Check for a restriction in the intake manifold.

Exhaust System Check

Check the exhaust system for a possible restriction. Refer to Exhaust Systems.

Engine Mechanical Checks

Check the engine for the following:

    • Improper valve timing
    • Low compression
    • Bent pushrods
    • Worn rocker arms
    • Broken or weak valve springs
    • Worn camshaft lobes

Additional Checks

Check the Service Bulletins for control module software updates.

Hard Start MFI

Checks

Action

Definition: The engine cranks OK, but does not start for a long time. The engine does eventually run, or may start but immediately dies.

Preliminary Checks
    • Refer to Symptoms .
    • Make sure the driver is using the correct starting procedure.

Sensor Checks

Check the Engine Coolant Temperature (ECT) sensor. Use the Scan Tool in order to compare the engine coolant temperature with the ambient air temperature on a cold engine. If the coolant temperature reading is more than 5° greater or less than the ambient air temperature on a cold engine, check for a high resistance in the coolant sensor circuit or the sensor itself.

Fuel System Checks
    • Check the supply to the injection pump. Refer to Fuel Supply System Check .
    • Check for air in the fuel system. Refer to Fuel Supply System Check .
    • Check the fuel return from the injection pump. Refer to Fuel Return System Diagnosis .
    • Check the engine shut-off solenoid operation.
    • Check the fuel injection nozzles. Refer to Injection Nozzle(s) Diagnosis .
    • Check the fuel tank cap vent.
    • Check for an internal injection pump problem. Refer to Fuel Injection System Diagnosis .

Electrical System Checks
    • Check the glow plug operation. Refer to Glow Plug System Check .
    • Check for slow cranking speed.

Air Intake System Checks
    • Check the air cleaner and the air intake ducts for a restriction.
    • Check for a restriction in the intake manifold.

Exhaust System Check

Check the exhaust system for a possible restriction. Refer to Exhaust Systems.

Engine Mechanical Checks

Check the engine for the following:

    • Improper valve timing
    • Low compression
    • Bent pushrods
    • Worn rocker arms
    • Broken or weak valve springs
    • Worn camshaft lobes

Additional Checks

Check the Service Bulletins for control module software updates.