Chevrolet Silverado / GMC Sierra. Service manual — part 10

ENGINE WILL NOT CRANK - CRANKSHAFT WILL NOT ROTATE

as required.

Worn, damaged, or improperly installed
crankshaft bearing

1. Inspect the crankshaft bearings.

2. Inspect the crankshaft journals.

3. Repair or replace damaged components

as required.

Cause

Correction

Seized accessory drive system component

1. Remove accessory drive belts.

2. Rotate crankshaft by hand at the

balancer or flywheel location.

Hydraulically locked cylinder

Coolant/antifreeze in cylinder

Oil in cylinder

Fuel in cylinder

1. Remove spark plugs and check for

fluid.

2. Inspect for broken head gasket.

3. Inspect for cracked engine block or

cylinder head.

4. Inspect for a sticking fuel injector.

Seized automatic transmission torque
converter

1. Remove the torque converter bolts.

2. Rotate crankshaft by hand at the

balancer or flywheel location.

Seized manual transmission

1. Disengage the clutch.

2. Rotate crankshaft by hand at the

balancer or flywheel location.

Broken timing chain and/or gears

Inspect timing chain and gears.

Repair as required.

Seized balance shaft

Inspect balance shaft.

Repair as required.

Material in cylinder

Broken valve

Piston material

Foreign material

Inspect cylinder for damaged
components and/or foreign materials.

Repair or replace as required.

Seized crankshaft or connecting rod bearings

Inspect crankshaft and connecting rod

2008 Chevrolet Silverado 1500

2008 ENGINE Engine Mechanical - 4.3L - Sierra & Silverado

COOLANT IN COMBUSTION CHAMBER

bearings.

Repair as required.

Bent or broken connecting rod

Inspect connecting rods.

Repair as required.

Broken crankshaft

Inspect crankshaft.

Repair as required.

Cause

Correction

DEFINITION: Excessive white smoke and/or coolant type odor coming from the exhaust
pipe may indicate coolant in the combustion chamber. Low coolant levels, an inoperative
cooling fan, or a faulty thermostat may lead to an "overtemperature" condition which may
cause engine component damage.

1. A slower than normal cranking speed may indicate coolant entering the combustion

chamber. Refer to Engine Will Not Crank - Crankshaft Will Not Rotate.

2. Remove the spark plugs and inspect for spark plugs saturated by coolant or coolant in

the cylinder bore.

3. Inspect by performing a cylinder leak-down test. During this test, excessive air

bubbles within the coolant may indicate a faulty gasket or damaged component.

4. Inspect by performing a cylinder compression test. Two cylinders "side-by-side" on

the engine block, with low compression, may indicate a failed cylinder head gasket.
Refer to Engine Compression Test.

Cracked intake manifold or failed gasket

Replace the components as required.

Faulty cylinder head gasket

Replace the head gasket and components as
required. Refer to Cylinder Head Cleaning
and Inspection and Cylinder Head
Replacement - Left Side or Cylinder Head
Replacement - Right Side.

Warped cylinder head

Machine the cylinder head to the proper
flatness, if applicable and replace the cylinder
head gasket. Refer to Cylinder Head
Cleaning and Inspection.

Cracked cylinder head

Replace the cylinder head and gasket.

Cracked cylinder liner or engine block

Replace the components as required.

2008 Chevrolet Silverado 1500

2008 ENGINE Engine Mechanical - 4.3L - Sierra & Silverado

COOLANT IN ENGINE OIL

ENGINE COMPRESSION TEST

1. Ensure that the vehicle batteries are in good condition, and fully charged.

2. Operate the vehicle until the engine is at normal operating temperature.

3. Disconnect the positive ignition coil wire plug from the ignition coil.

Cylinder head or engine block porosity

Replace the components as required.

Cause

Correction

DEFINITION: Foamy or discolored oil or an engine oil "overfill" condition may indicate
coolant entering the engine crankcase. Low coolant levels, an inoperative cooling fan, or a
faulty thermostat may lead to an "overtemperature" condition which may cause engine
component damage. Contaminated engine oil and oil filter should be changed.

1. Inspect the oil for excessive foaming or an overfill condition. Oil diluted by coolant

may not properly lubricate the crankshaft bearings and may lead to component
damage. Refer to Lower Engine Noise, Regardless of Engine Speed.

2. Inspect by performing a cylinder leak-down test. During this test, excessive air

bubbles within the cooling system may indicate a faulty gasket or damaged
component.

3. Inspect by performing a cylinder compression test. Two cylinders "side-by-side" on

the engine block with low compression may indicate a failed cylinder head gasket.
Refer to Engine Compression Test.

Faulty external engine oil cooler

Replace the components as required.

Faulty cylinder head gasket

Replace the head gasket and components as
required. Refer to Cylinder Head Cleaning
and Inspection and Cylinder Head
Replacement - Left Side or Cylinder Head
Replacement - Right Side.

Warped cylinder head

Machine the cylinder head to proper flatness,
if applicable, and replace the cylinder head
gasket. Refer to Cylinder Head Cleaning
and Inspection.

Cracked cylinder head

Replace the cylinder head and gasket.

Cracked cylinder liner or engine block

Replace the components as required.

Cylinder head, block, or manifold porosity

Replace the components as required.

2008 Chevrolet Silverado 1500

2008 ENGINE Engine Mechanical - 4.3L - Sierra & Silverado

4. Disconnect the fuel injector electrical connector.

5. Remove all of the spark plugs.

6. Block the throttle linkage wide open.

7. Install the engine cylinder compression gage to the cylinder being tested.

8. Using the vehicle starter motor, rotate, or crank the engine for 4 compression strokes, or

puffs, for the cylinder being tested. If the engine rotates for more than 4 compression
strokes, test the cylinder again.

9. Record the compression reading.

10. Remove the engine cylinder compression gage from the cylinder being tested.

11. Repeat steps 8-11 for each additional cylinder. All cylinders must be tested to obtain valid

test results.

12. If any cylinders have low compression, inject approximately 15 ml (1 oz) of engine oil into

the cylinder through the spark plug hole.

13. Repeat steps 8-11 for all low compression cylinders.

14. The minimum compression in any one cylinder should not be less than 70 percent of the

highest cylinder. No cylinder should read less than 690 kpa (100 psi). For example, if the
highest pressure in any one cylinder is 1035 kPa (150 psi), the lowest allowable pressure for
any other cylinder would be 725 kPa (105 psi). Multiply the highest cylinder pressure by 70
percent, 1035 kPa x 70 percent = 725 kPa (150 psi x 70 percent = 105 psi), in order to
determine the lowest allowable pressure in any other cylinder.

Normal

The compression builds up quickly and evenly to the specified compression.

Piston rings leaking

Compression is low on the first compression stroke. The compression builds up on the
following strokes, but does not reach normal. Compression improves considerably
when you add oil.

Valves leaking

Compression is low on the first compression stroke. The compression does not build up

NOTE:

Do not insert objects into the throttle plate opening. Damage to
the throttle body can result, requiring replacement of the
throttle body assembly.

2008 Chevrolet Silverado 1500

2008 ENGINE Engine Mechanical - 4.3L - Sierra & Silverado