Hummer H2. Manual - part 26

Oil pickup screen or tube blocked 

Remove restriction 

Loose oil inlet tube 

Tighten oil inlet tube 

Loose camshaft bearings 

Replace camshaft bearings, See ENGINES 

Internal leakage at oil passages 

Replace block or cylinder head 

Low Oil Pressure 

Low engine oil level 

Add oil to proper level 

Engine oil too thin 

Remove and replace with thicker oil 

Excessive oil pump clearance 

Reduce oil pump clearance, See ENGINES 

Oil pickup tube or screen blocked 

Remove restrictions 

Main, rod or cam bearing clearance 
excessive 

Replace bearing to reduce clearance, See 

ENGINES 

High Oil Pressure 

Improper grade of oil 

Replace with proper oil 

Oil pressure relief valve stuck closed 

Eliminate binding 

Oil pressure sender or gauge faulty 

Replace sender or gauge 

Noisy Main Bearings 

Inadequate oil supply 

Check oil delivery to main bearings 

Excessive main bearing clearance 

Replace main bearings, See ENGINES 

Excessive crankshaft end play 

Replace crankshaft, See ENGINES 

Loose flywheel or torque converter 

Tighten attaching bolts 

Loose or damaged vibration damper 

Tighten or replace vibration damper 

Crankshaft journals out-of-round 

Re-grind crankshaft journals 

Excessive belt tension 

Loosen belt tension 

Noisy Connecting Rods 

Excessive bearing clearance or missing 
bearing 

Replace bearing, See ENGINES 

Crankshaft rod journal out-of-round 

Re-grind crankshaft journal 

Misaligned connecting rod or cap 

Remove rod or cap and realign 

Incorrectly tightened rod bolts 

Remove and re-tighten rod bolts 

Noisy Pistons and Rings 

Excessive piston-to-bore clearance 

Install larger pistons, See ENGINES 

Bore tapered or out-of-round 

Rebore block 

Piston ring broken 

Replace piston rings, See ENGINES 

Piston pin loose or seized 

Replace piston pin, See ENGINES 

Connecting rods misaligned 

Realign connecting rods 

Ring side clearance too loose or tight 

Replace with larger or smaller rings 

Carbon build-up on piston 

Remove carbon 

Noisy Valve Train 

Worn or bent push rods 

Replace push rods, See ENGINES 

 

1998 Chevrolet Pickup C1500 

GENERAL INFORMATION Trouble Shooting - Basic Procedures

  

Worn rocker arms or bridged pivots 

Replace push rods, See ENGINES 

Dirt or chips in valve lifters 

Remove lifters and remove dirt/chips 

Excessive valve lifter leak-down 

Replace valve lifters, See ENGINES 

Valve lifter face worn 

Replace valve lifters, See ENGINES 

Broken or cocked valve springs 

Replace or reposition springs 

Too much valve stem-to-guide 
clearance 

Replace valve guides, See ENGINES 

Valve bent 

Replace valve, See ENGINES 

Loose rocker arms 

Retighten rocker arms, See ENGINES 

Excessive valve seat run-out 

Reface valve seats, See ENGINES 

Missing valve lock 

Install new valve lock 

Excessively worn camshaft lobes 

Replace camshaft, See ENGINES 

Plugged valve lifter oil holes 

Eliminate restriction or replace lifter 

Faulty valve lifter check ball 

Replace lifter check ball, See ENGINES 

Rocker arm nut installed upside down 

Remove and reinstall correctly 

Valve lifter incorrect for engine 

Remove and replace valve lifters 

Faulty push rod seat or lifter plunger 

Replace plunger or push rod 

Noisy Valves 

Improper valve lash 

Re-adjust valve lash, See ENGINES 

Worn or dirty valve lifters 

Clean and/or replace lifters 

Worn valve guides 

Replace valve guides, See ENGINES 

Excessive valve seat or face run-out 

Reface seats or valve face 

Worn camshaft lobes 

Replace camshaft, See ENGINES 

Loose rocker arm studs 

Re-tighten rocker arm studs, See ENGINES 

Bent push rods 

Replace push rods, See ENGINES 

Broken valve springs 

Replace valve springs, See ENGINES 

Burned,Sticking or Broken Valves 

Weak valve springs or warped valves 

Replace valves and/or springs, See 

ENGINES 

Improper lifter clearance 

Re-adjust clearance or replace lifters 

Worn guides or improper guide 
clearance 

Replace valve guides, See ENGINES 

Out-of-round valve seats or improper 
seat width 

Re-grind valve seats 

Gum deposits on valve stems, seats or 
guide 

Remove deposits 

Improper spark timing 

Re-adjust spark timing 

Broken Pistons/Rings 

Undersize pistons 

Replace with larger pistons, See ENGINES 

Wrong piston rings 

Replace with correct rings, See ENGINES 

 

1998 Chevrolet Pickup C1500 

GENERAL INFORMATION Trouble Shooting - Basic Procedures

  

ENGINE PERFORMANCE 

CARBURETOR TROUBLE SHOOTING: 

BASIC COLD START SYMPTOMS TROUBLE SHOOTING CHART 

Out-of-round cylinder bore 

Re-bore cylinder bore 

Improper connecting rod alignment 

Remove and realign connecting rods 

Excessively worn ring grooves 

Replace pistons, See ENGINES 

Improperly assembled piston pins 

Re-assemble pin-to-piston, See ENGINES 

Insufficient ring gap clearance 

Install new rings, See ENGINES 

Engine overheating 

Check cooling system 

Incorrect ignition timing 

Re-adjust ignition timing, See TUNE-UP 

Excessive Exhaust Noise 

Leaks at manifold to head, or to pipe 

Replace manifold or pipe gasket 

Exhaust manifold cracked or broken 

Replace exhaust manifold, See ENGINES 

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 

Engine Won't Start 

Choke not closing 

Check choke operation, see FUEL SYSTEMS 

Choke linkage bent 

Check linkage, see FUEL SYSTEM 

Engine Starts, Then Dies 

Choke vacuum kick setting too wide  Check setting and adjust see, FUEL SYSTEMS 

Fast idle RPM too low 

Reset RPM to specification, see TUNE-UP 

Fast idle cam index incorrect 

Reset fast idle cam index, see FUEL SYSTEMS 

Vacuum leak 

Inspect vacuum system for leaks 

Low fuel pump outlet 

Repair or replace pump, see FUEL SYSTEMS 

Low carburetor fuel level 

Check float setting see FUEL SYSTEM 

Engine Quits Under Load 

Choke vacuum kick setting incorrect  Reset vacuum kick setting,see FUEL SYSTEMS 

Fast idle cam index incorrect 

Reset fast idle cam index, see FUEL SYSTEM 

Incorrect hot fast idle speed RPM 

Reset fast idle RPM, see TUNE-UP 

Engine Starts, Runs Up, Then Idles, Slowly With Black Smoke 

Choke vacuum kick set too narrow 

Reset vacuum kick, see FUEL SYSTEMS 

Fast idle cam index incorrect 

Reset fast idle cam index, see FUEL SYSTEMS 

 

1998 Chevrolet Pickup C1500 

GENERAL INFORMATION Trouble Shooting - Basic Procedures

  

BASIC HOT START SYMPTOMS TROUBLE SHOOTING CHART 

BASIC COLD ENGINE DRIVEABILITY SYMPTOMS TROUBLE SHOOTING CHART 

BASIC WARM ENGINE DRIVEABILITY SYMPTOMS TROUBLE SHOOTING CHART 

Hot fast idle RPM too low 

Reset fast idle RPM, see TUNE-UP 

CONDITION & POSSIBLE CAUSE 

CORRECTION 

Engine Won't Start 

Engine flooded 

Allow fuel to evaporate 

CONDITION & POSSIBLE 
CAUSE 

CORRECTION 

Engine Stalls in Gear 

Choke vacuum kick setting 
incorrect 

Reset choke vacuum kick, see FUEL SYSTEMS 

Fast idle RPM incorrect 

Reset fast idle RPM, see TUNE-UP 

Fast idle cam index incorrect 

Reset fast idle cam see FUEL SYSTEMS 

Acceleration Sag or Stall 

Defective choke control switch 

Replace choke control switch 

Choke vacuum kick setting 
incorrect 

Reset choke vacuum kick see, FUEL SYSTEMS 

Float level incorrect (too low) 

Adjust float level, FUEL SYSTEMS 

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 

 

1998 Chevrolet Pickup C1500 

GENERAL INFORMATION Trouble Shooting - Basic Procedures