Chevrolet Silverado / GMC Sierra. Service manual — part 1222

BASIC WARM ENGINE DRIVEABILITY SYMPTOMS TROUBLE SHOOTING
CHART

Accelerator pump defective

Repair or replace pump

see FUEL SYSTEMS

Secondary throttles not closed

Inspect lockout

adjustment, see FUEL

SYSTEMS

Sag or Stall After Warmup

Defective choke control switch

Replace choke control

switch, see FUEL

SYSTEMS

Defective accelerator pump

Replace pump, see FUEL

SYSTEMS

Float level incorrect (too low)

Adjust float level, see

FUEL SYSTEMS

Backfiring & Black Smoke

Plugged heat crossover system

Remove restriction

CONDITION & POSSIBLE CAUSE

CORRECTION

Hesitation With Small Amount of Gas Pedal Movement

Vacuum leak

Inspect vacuum lines

Accelerator pump weak or inoperable

Replace pump, see FUEL

SYSTEMS

Float level setting too low

Reset float level,

see,FUEL SYSTEMS

Metering rods sticking or binding

Inspect and/or replace

rods, see FUEL

SYSTEMS

Carburetor idle or transfer system plugged

Inspect system and remove

restriction

Frozen or binding heated air inlet

Inspect heated air door for

binding

Hesitation With Heavy Gas Pedal Movement

Defective accelerator pump

Replace pump, see FUEL

SYSTEMS

Metering rod carrier sticking or binding

Remove restriction

Large vacuum leak

Inspect vacuum system and

2008 Chevrolet Silverado 1500

GENERAL INFORMATION Trouble Shooting - Basic Procedures

DIESEL ENGINE TROUBLE SHOOTING

BASIC DIESEL ENGINE TROUBLE SHOOTING CHART

repair leak

Float level setting too low

Reset float level, see

FUEL SYSTEMS

Defective fuel pump, lines or filter

Inspect pump, lines and

filter

Air door setting incorrect

Adjust air door setting, see

FUEL

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.

NOTE:

Diesel engines mechanical diagnosis is the same as gasoline
engines for items such as noisy valves, bearings, pistons, etc. The
following trouble shooting covers only items pertaining to diesel
engines.

CONDITION & POSSIBLE CAUSE

CORRECTION

Engine Won't Crank

Bad battery connections or dead batteries

Check connections and/or

replace batteries

Bad starter connections or bad starter

Check connections and/or

replace starter

Engine Cranks Slowly, Won't Start

Bad battery connections or dead batteries

Check connections and/or

replace batteries

Engine oil too heavy

Replace engine oil

Engine Cranks Normally, But Will Not Start

Glow plugs not functioning

Check glow plug system,

see FUEL SYSTEMS

Glow plug control not functioning

Check controller, see

2008 Chevrolet Silverado 1500

GENERAL INFORMATION Trouble Shooting - Basic Procedures

FUEL SYSTEMS

Fuel not injected into cylinders

Check fuel injectors, see

FUEL SYSTEMS

No fuel to injection pump

Check fuel delivery system

Fuel filter blocked

Replace fuel filter

Fuel tank filter blocked

Replace fuel tank filter

Fuel pump not operating

Check pump operation

and/or replace pump

Fuel return system blocked

Inspect system and remove

restriction

No voltage to fuel solenoid

Check solenoid and

connections

Incorrect or contaminated fuel

Replace fuel

Incorrect injection pump timing

Re-adjust pump timing, see

FUEL SYSTEMS

Low compression

Check valves, pistons,

rings, see ENGINES

Injection pump malfunction

Inspect and/or replace

injection pump

Engine Starts, Won't Idle

Incorrect slow idle adjustment

Reset idle adjustment, see

TUNE-UP

Fast idle solenoid malfunctioning

Check solenoid and

connections

Fuel return system blocked

Check system and remove

restrictions

Glow plugs go off too soon

See glow plug diagnosis in

FUEL SYSTEMS

Injection pump timing incorrect

Reset pump timing, see

FUEL SYSTEMS

No fuel to injection pump

Check fuel delivery system

Incorrect or contaminated fuel

Replace fuel

Low compression

Check valves, piston, rings,

see ENGINES

Injection pump malfunction

Replace injection pump,

see FUEL SYSTEMS

Fuel solenoid closes in RUN position

Check solenoid and

2008 Chevrolet Silverado 1500

GENERAL INFORMATION Trouble Shooting - Basic Procedures

connections

Engines Starts/Idles Rough W/out Smoke or Noise

Incorrect slow idle adjustment

Reset slow idle, see

TUNE-UP

Injection line fuel leaks

Check lines and

connections

Fuel return system blocked

Check lines and

connections

Air in fuel system

Bleed air from system

Incorrect or contaminated fuel

Replace fuel

Injector nozzle malfunction

Check nozzles, see FUEL

SYSTEMS

Engines Starts and Idles Rough W/out Smoke or Noise, But Clears After Warm-Up

Injection pump timing incorrect

Reset pump timing, see

FUEL SYSTEMS

Engine not fully broken in

Put more miles on engine

Air in system

Bleed air from system

Injector nozzle malfunction

Check nozzles, see FUEL

SYSTEMS

Engine Idles Correctly, Misfires Above Idle

Blocked fuel filter

Replace fuel filter

Injection pump timing incorrect

Reset pump timing, see

FUEL SYSTEMS

Incorrect or contaminated fuel

Replace fuel

Engine Won't Return To Idle

Fast idle adjustment incorrect

Reset fast idle, see TUNE-

UP

Internal injection pump malfunction

Replace injection pump,

see FUEL SYSTEMS

External linkage binding

Check linkage and remove

binding

Fuel Leaks On Ground

Loose or broken fuel line

Check lines and

connections

Internal injection pump seal leak

Replace injection pump,

see FUEL SYSTEMS

2008 Chevrolet Silverado 1500

GENERAL INFORMATION Trouble Shooting - Basic Procedures