Hummer H2. Instruction - page 71
Poor Acceleration
Incorrect Ignition Timing
Reset Timing
Leaky Valves
Check Compression
Component Failure
Spark Arcing
Replace Faulty Part
Defective Pick-Up Coil
Replace Pick-Up Coil
Defective Ignition Coil
Replace Ignition Coil
Defective Control Unit
Replace Control Unit
Ignition Diagnosis By Scope Pattern
All Firing Lines Abnormally High
Retarded Ignition Timing
Reset Ignition Timing
Lean Air/Fuel Mixture
Adjust Fuel Mixture
High Secondary Resistance
Repair Secondary Ignition
All Firing Lines Abnormally Low
Rich Air/Fuel Mixture
Adjust Air/Fuel Mixture
Arcing Coil Wire
Replace Coil Wire
Cracked Coil
Replace Coil
Low Coil Output
Replace Coil
Low Compression
Check/Repair Engine
Several High Firing Lines
Fuel Mixture Unbalanced
Check Fuel System
EGR Valve Stuck Open
Clean/Replace EGR Valve
High Plug Wire Resistance
Replace Plug Wire
Cracked/Broken Plugs
Replace Plugs
Intake Vacuum Leak
Repair Leak
Several Low Firing Lines
Fuel Mixture Unbalanced
Adjust Fuel Mixture
Plug Wires Arcing
Replace Plug Wires
Cracked Coil Arcing
Replace Coil
Uneven Compression
Check/Repair Engine
Faulty Spark Plugs
Replace Plugs
Cylinders Not Firing
Cracked Distributor Cap
Replace Cap
Shorted Plug Wires
Replace Plug Wires
Mechanical Engine Fault
Check/Repair Engine
Spark Plugs Fouled
Replace Plugs
Carbon Track in Distributor Cap
Replace Cap
Hard Starting
Defective Ignition Coil(s)
Replace Coil(s)
1998 Chevrolet Pickup C1500
GENERAL INFORMATION TROUBLE SHOOTING
FUEL INJECTION TROUBLE SHOOTING
Fouled Spark Plugs
Replace Plugs
Incorrect Timing
Reset Ignition Timing
Problem & Possible Cause
Action
Cold Start Valve Inoperative
Test Cold Start Valve
Poor Vacuum/Electrical Connection
Repair Connections
Contaminated Fuel
Test Fuel for Water/Alcohol
Bad Fuel Pump Relay/Circuit
Test Relay/Wiring
Battery Voltage Low
Charge/Test Battery
Low Fuel Pressure
Test Press. Regulator/Pump
No Distributor Reference Pulse
Repair Ignition System
Coolant Temp. Sensor Defective
Test Temp. Sensor/Circuit
No Power To Injectors
Check Injector Fuse/Relay
Hard Starting
Defective Idle Air Control (IAC)
Test IAC and Circuit
EGR Valve Open
Test EGR Valve/Control Circuit
Restricted Fuel Lines
Inspect/Replace Fuel Lines
Poor MAP Sensor Signal
Test MAP Sensor/Circuit
Engine Stalls During Parking Maneuver
Check P.S. Press. Switch
Rough Idle
Dirty Fuel Injectors
Clean/Replace Injectors
Poor MAP Sensor Signal
Test MAP Sensor/Circuit
Intermittent Fuel Injector Operation
Check Harness Connectors
Erratic Vehicle Speed Sensor Inputs
Harness Too Close to Plug Wires
Poor O
2
Sensor Signal
Test O
2
Sensor/Circuit
Faulty PCV System
Check PCV Valve and Hoses
Poor Acceleration
Weak Fuel Pump
Replace Fuel Pump
Dirty Fuel Injectors
Clean/Replace Injectors
Excessive Intake Valve Deposits
Clean Intake System
Poor High Speed Operation
Low Fuel Pump Volume
Faulty Fuel Pump/Filter
Poor MAP Sensor Signal
Test Speed Sensor/Circuit
Acceleration Ping/Knock
Faulty EGR System
Check EGR Valve and Hoses
Poor Knock Sensor Signal
Test Knock Sensor/Circuit
Poor Baro Sensor Signal
Test Baro Sensor/Circuit
Improper Ignition Timing
Adjust Timing
1998 Chevrolet Pickup C1500
GENERAL INFORMATION TROUBLE SHOOTING
Engine Overheating
Check Cooling System
Poor Quality Fuel
Use Different Fuel
Carbon Build-Up
Decarbon Engine
1998 Chevrolet Pickup C1500
GENERAL INFORMATION TROUBLE SHOOTING
GENERAL INFORMATION
Gear Tooth Contact Patterns
INSPECTION
Wipe lubricant from internal parts. Rotate gears and inspect for wear or damage. Mount dial indicator to
housing and check backlash at several points around ring gear. Backlash must be within specification at all
points. If no defects are found, check gear tooth pattern contact.
GEAR TOOTH CONTACT PATTERN
1. Paint ring gear teeth with marking compound. Wrap cloth or rope around drive pinion flange to act as
brake. Rotate gear until clear contact pattern is obtained.
2. Contact pattern will indicate whether correct pinion bearing mounting shim has been installed and if drive
gear backlash has been set properly. Backlash between drive gear pinion must be maintained within
specified limits until correct tooth pattern is obtained.
ADJUSTMENTS
GEAR BACKLASH & PINION SHIM CHANGES
1. With no change in backlash, moving pinion further from ring gear moves drive pattern toward heel and
top of tooth, and moves coast pattern toward toe and top of tooth.
2. With no change in backlash, moving pinion closer to ring gear moves drive pattern toward toe and bottom
of tooth, and moves coast pattern toward heel and bottom of tooth.
3. With no change in pinion shim thickness, an increase in backlash moves ring gear further from pinion.
Both drive and coast patterns move toward heel and top of tooth.
4. With no change in pinion shim thickness, a decrease in backlash moves ring gear closer to pinion gear.
Both drive and coast patterns move toward toe and bottom of tooth.
NOTE:
Drive pattern should be well centered on ring gear teeth. Coast pattern should
be centered, but may be slightly toward toe of ring gear teeth.
1998 Chevrolet Pickup C1500
GENERAL INFORMATION Gear Tooth Contact Patterns
1998 Chevrolet Pickup C1500
GENERAL INFORMATION Gear Tooth Contact Patterns