Chevrolet Silverado / GMC Sierra. Service manual — part 1225

Burned solenoid contacts

Replace solenoid

Faulty starter

Replace starter

Starter Engages Engine Only Momentarily

Engine timing too far advanced

See Ignition Timing in

TUNE-UP article

Overrunning clutch not engaging properly

Replace overrunning

clutch. See STARTER

article

Broken starter clutch

See STARTER article

Broken teeth on engine flywheel

Replace flywheel and

check starter pinion gear

for damage

Weak drive assembly thrust spring

See STARTER article

Weak hold-in coil

See Bench Tests in

STARTER article

Starter Drive Will Not Engage

Defective point assembly

See Testing in STARTER

article

Poor point assembly ground

See Testing in STARTER

article

Defective pull-in coil

Replace starter solenoid

Starter Relay Does Not Close

Dead battery

Charge or replace battery

as necessary

Faulty wiring

Check all wiring and

connections leading to

relay

Neutral safety switch faulty

Replace neutral safety

switch

Starter relay faulty

Replace starter relay

Starter Drive Will Not Disengage

Starter motor loose on mountings

Tighten starter attach

bolts

Worn drive end bushing

See STARTER article

Damaged engine flywheel teeth

Replace flywheel and

starter pinion gear for

damage

2008 Chevrolet Silverado 1500

GENERAL INFORMATION Trouble Shooting - Basic Procedures

Drive yolk return spring broken or missing

Replace return spring

Faulty ignition switch

Replace ignition switch

Insufficient clearance between winding leads to solenoid
terminal and main contact in solenoid

Replace starter solenoid

Starter clutch not disengaging

Replace starter clutch

Ignition starter switch contacts sticking

Replace ignition switch

Starter Relay Operates but Solenoid Does Not

Faulty solenoid switch, switch connections or relay

Check all wiring between

relay and solenoid or

replace relay or solenoid

as necessary

Broken lead or loose soldered connections

Repair wire or wire

connections as necessary

Solenoid Plunger Vibrates When Switch is Engaged

Weak battery

Charge or replace battery

as necessary

Solenoid contacts corroded

Clean contacts or replace

solenoid

Faulty wiring

Check all wiring leading

to solenoid

Broken connections inside switch cover

Repair connections or

replace solenoid

Open hold-in wire

Replace solenoid

Low Current Draw

Worn brushes or weak

Replace brushes or brush

springs as necessary

High Pitched Whine During Cranking Before Engine Fires but Engine Fires and Cranks
Normally

Distance too great between starter pinion and flywheel

Align starter or check

that correct starter and

flywheel are being used

High Pitched Whine After Engine Fires With Key released. Engine Fires and Cranks
Normally

Distance too small between starter pinion and flywheel

Flywheel runout

contributes to the

intermittent nature

2008 Chevrolet Silverado 1500

GENERAL INFORMATION Trouble Shooting - Basic Procedures

TUNE-UP TROUBLE SHOOTING - GAS ENGINE VEHICLES

BASIC SPARK PLUG TROUBLE SHOOTING CHARTS

NOTE:

This is GENERAL information. This article is not intended to be
specific to any unique situation or individual vehicle configuration.
The purpose of this Trouble Shooting information is to provide a list
of common causes to problem symptoms. For model-specific
Trouble Shooting, refer to SUBJECT, DIAGNOSTIC, or TESTING
articles available in the section(s) you are accessing.

CONDITION & POSSIBLE CAUSE

CORRECTION

Normal Spark Plug Condition

Light Tan or Gray deposits

No Action

Electrode not burned or fouled

No Action

Gap tolerance not changed

No Action

Cold Fouling or Carbon Deposits

Overrich air/fuel mixture

Adjust air/fuel mixture, see

ENGINE

PERFORMANCE section

Faulty choke

Replace choke assembly,

see ENGINE

PERFORMANCE section

Clogged air filter

Clean and/or replace air

filter

Incorrect idle speed or dirty carburetor

Reset idle speed and/ or

clean carburetor

Faulty ignition wires

Replace ignition wiring

Prolonged operation at idle

Shut engine off during

long idle

Sticking valves or worn valve guide seals

Check valve train

Wet Fouling or Oil Deposits

Worn rings and pistons

Install new rings and

pistons

Excessive cylinder wear

Rebore or replace block

Excessive valve guide clearance

Worn or loose bearing

Gap Bridged

Deposits in combustion chamber becoming fused to

Clean combustion chamber

2008 Chevrolet Silverado 1500

GENERAL INFORMATION Trouble Shooting - Basic Procedures

BASIC ELECTRONIC IGNITION TROUBLE SHOOTING CHARTS

electrode

of deposits

Blistered Electrode

Engine overheating

Check cooling system

Wrong type of fuel

Replace with correct fuel

Loose spark plugs

Retighten spark plugs

Over-advanced ignition timing

Reset ignition timing see

ENGINE

PERFORMANCE

Pre-Ignition or Melted Electrodes

Incorrect type of fuel

Replace with correct fuel

Incorrect ignition timing

Reset ignition timing see

ENGINE

PERFORMANCE

Burned valves

Replace valves

Engine Overheating

Check cooling system

Wrong type of spark plug, too hot

Replace with correct spark

plug, see ENGINE

PERFORMANCE

Chipped Insulators

Severe detonation

Check for over-advanced

timing or combustion

Improper gapping procedure

Re-gap spark plugs

Rust Colored Deposits

Additives in unleaded fuel

Try different fuel brand

Water In Combustion Chamber

Blown head gasket or cracked head

Repair or replace head or

head gasket

NOTE:

Before diagnosing an electronic ignition system, ensure that all
wiring is connected properly between distributor, wiring connector
and spark plugs. Ignition problem will show up either as: Engine
Will Not Start or Engine Runs Rough.

CONDITION & POSSIBLE CAUSE

CORRECTION

Engine Won't Start

2008 Chevrolet Silverado 1500

GENERAL INFORMATION Trouble Shooting - Basic Procedures