Vanguard BIG BLOCK M540000, Repair Manual, Page: 32 / 168

Gasoline-Fueled Engine Troubleshooting Chart
Gasoline-Fueled Engine Troubleshooting Chart
Problem Potential Cause Action
Worn or fouled spark plug Replace spark plug with new and
gap to recommended specification
Air cleaner plugged Clean or replace air filter. See SECTION 2
- MAINTENANCE - Clean/Replace Air Filter
Choke partly closed (carbureted engine) Open choke; if necessary,
adjust choke cable/control
Fuel mixture too lean Service carburetor or fuel injection
system. See SECTION 6 - SERVICE
ENGINE SUBASSEMBLIES - Carburetor
See EFI Diagnostics Manual
Fuel system vent lines blocked or restricted Clean or replace fuel system vent lines and port
Fuel not reaching carburetor or fuel injectors Clean fuel tank, clean or replace fuel lines
and filters, check fuel pump operation.
Ignition shutoff switch not in full ON position Move or adjust shutoff switch to full ON position
Engine running too hot See "Engine overheats"
Exhaust system restriction Clean exhaust ports; remove
and clean or replace muffler
Low compression Check engine compression
components. See Check Compression
ComponentsCheck Compression Components
Weak or damaged valve springs Replace valve springs. See SECTION 6
- SERVICE ENGINE SUBASSEMBLIES
- Cylinder head valve springs
Low engine oil Check engine oil level. See SECTION
2 - MAINTENANCE - Check Engine Oil
Air cooling system blocked with dirt and debris Clean air cooling system. See SECTION 2 -
MAINTENANCE - Clean Air Cooling System
Missing air cooling shrouds Replace air cooling shrouds
Fuel system too lean Service carburetor or fuel injection
system. See SECTION 6 - SERVICE
ENGINE SUBASSEMBLIES - Carburetor
See EFI Diagnostics Manual
Ignition system out of time Check crankshaft/flywheel key for wear
or damage. See SECTION 6 - SERVICE
ENGINE SUBASSEMBLIES - Flywheel,
Crankshaft, Crankcase CoverSECTION 6
- SERVICE ENGINE SUBASSEMBLIES
- Flywheel, Crankshaft, Crankcase Cover
Engine overheats
Valves out of adjustment Adjust valves. See SECTION 7 -
ASSEMBLE ENGINE - Top End Assembly
Perform On-Board Diagnostics
(OBD) test (EFI engines)
See applicable EFI Diagnostic and
Repair manual for your engine
Faulty engine wiring or ECM connector See applicable EFI Diagnostic and
Repair manual for your engine
Fuel system vents and lines plugged or restricted Clean or replace fuel system vent lines and ports
Carburetor float level too low Service carburetor. See SECTION 6 - SERVICE
ENGINE SUBASSEMBLIES - Carburetor
Fuel tank, fuel lines, fuel
filter plugged or restricted
Clean fuel tank, fuel lines, fuel filter and check
fuel system components for dirt and debri
Governor linkage binding Clean and repair governor linkage
Static governor adjustment not set properly Set governor static adjustment. See SECTION 2
- MAINTENANCE - Static Governor Adjustment
Throttle or throttle shaft binding Clean and adjust throttle and throttle shaft
Throttle or governor springs unhooked,
broken, or in the wrong position
Connect or replace broken springs
or return springs to correct position
Carburetor out of adjustment or internal
parts clogged with dirt and debris
Service carburetor. See SECTION 6 - SERVICE
ENGINE SUBASSEMBLIES - Carburetor
Engine surges, will not hold steady speed
Water or other contamination in fuel Drain tank, fuel system, and fuel
lines; replace with recommended fuel.
33