GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2003 🢒 TopKick C-Series (Conventional) C6/C7/C8 🢒 Engine 🢒 Engine Controls - 7.8L 🢒 Excessive Smoke

Excessive Smoke Black Smoke

Checks

Action

DEFINITION: Black smoke under load, idle or start up hot or cold.

Preliminary Check
    • Refer to Symptoms - Engine Controls .
    • Ensure the customer has an actual problem.
    • Inspect the fuel quality.
    • Inspect the oil viscosity.

Fuel System Checks
    • Inspect the fuel injection pump.
    • Inspect the fuel injectors.

Sensor Check
    • Inspect the engine coolant temperature (ECT) sensor. Use the scan tool in order to compare the ECT with the ambient air temperature on a cold engine. If the coolant temperature reading is more than 5 degrees more 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.
    • Inspect the boost sensor operation.
    • Inspect the BARO sensor operation.
    • Inspect the MAF sensor operation.
    • Inspect the glow plug system operation.
    • Inspect the fuel rail pressure (FRP) sensor. Use the scan tool to observe FRP with the engine OFF. FRP should be near 1.4 MPa. If not , check for high resistance in the low reference or 5-volt reference circuits or the sensor.

Air Intake System Check
    • Inspect the air cleaner and the air intake ducts for restriction.
    • Inspect for a restriction in the turbocharger charged air cooler.
    • Inspect for a restriction in the intake manifold.
    • Inspect the air ducts for air leaks between the turbocharger and the intake manifold.
    • Inspect the EGR valve operation
    • Inspect the turbocharger operation.

Engine Mechanical Check
    • Test for poor cylinder compression.
    • Test for incorrect basic engine parts such as the cam, the heads, the pistons, etc.
    • Test for excessive oil entering the combustion chamber.

Exhaust System Check
    • Test for proper exhaust brake operation.
    • Inspect the exhaust restrictions.

Excessive Smoke Blue or Gray Smoke

Checks

Action

DEFINITION: Gray or blue smoke under load, idle or start up hot or cold.

Preliminary Check
    • Refer to Symptoms - Engine Controls .
    • Make sure the customer has an actual problem.
    • Inspect the fuel quality. Refer to Fuel Specific Gravity Testing .

Fuel System Checks
    • Inspect the fuel injection pump.
    • Inspect the fuel injectors.

Sensor Check
    • Inspect the engine coolant temperature (ECT) sensor. Use the scan tool in order to compare the ECT with the ambient air temperature on a cold engine. If the coolant temperature reading is more than 5 degrees more 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.
    • Inspect the glow plug system operation.
    • Inspect the fuel rail pressure (FRP) sensor. Use the scan tool to observe FRP with the engine OFF. FRP should be near 1.4 MPa. If not , inspect for high resistance in the low reference or 5-volt reference circuits or the sensor.

Air Intake System Check
    • Inspect the air cleaner and the air intake ducts for restriction.
    • Inspect for a restriction in the turbocharger charged air cooler.
    • Inspect for a restriction in the intake manifold.

Engine Mechanical Check
    • Perform the cylinder leakage test.
    • Perform the cylinder compression test. Proper compression is more than 2157 kPa (313 psi).
    • Inspect for incorrect basic engine parts such as the cam, the heads, the pistons, piston rings, and valves.
    • Inspect for excessive oil entering the combustion chamber.

Turbocharger

Inspect for leaking seals in the turbocharger. A slight film on the intake side is normal.

Excessive Smoke White Smoke

Checks

Action

DEFINITION: White smoke under load, idle or start up hot or cold.

Preliminary Check
    • Refer to Symptoms - Engine Controls .
    • Ensure the customer has an actual problem.
    • Inspect the fuel quality. Refer to Fuel Specific Gravity Testing .

Fuel System Checks
    • If excessive smoke is present, check for a stuck open fuel injector.
        1. Disconnect all of the fuel injector harness connectors.
        2. Remove the glow plugs.

        Important: Do not stand in front of the glow plug holes while cranking the engine.

        3. Crank the engine while observing the holes for fuel spray.
        4. Replace the fuel injectors for the cylinders that spray fuel.
        5. Inspect for contaminated oil or high oil level. Change oil as necessary.
    • Inspect the fuel injection pump.
    • Inspect for plugged or inoperative fuel injectors.

Sensor Check
    • Inspect the Crankshaft position sensor and Camshaft position sensor operation.
    • Inspect the Intake Air Temperature sensor and Fuel Temperature sensor operation.
    • Inspect the engine coolant temperature (ECT) sensor. Use the scan tool in order to compare the ECT with the ambient air temperature on a cold engine. If the coolant temperature reading is more than 5 degrees more 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.
    • Inspect the glow plug system operation.
    • Inspect the fuel rail pressure (FRP) sensor. Use the scan tool to observe FRP with the engine OFF. FRP should be near 1.4 MPa. If not , check for high resistance in the low reference or 5-volt reference circuits or the sensor itself.

Air Intake System Check
    • Inspect the air cleaner and the air intake ducts for restriction.
    • Inspect for a restriction in the turbocharger charged air cooler.
    • Inspect for a restriction in the intake manifold.
    • Inspect the intake air heater (IAH) for proper operation.

Engine Mechanical Check
    • Inspect for incorrect basic engine parts such as the cam, the heads, the pistons, etc.
    • Inspect for coolant entering the combustion chamber.