Vanguard BIG BLOCK M540000, Repair Manual, Page: 31 / 168

Troubleshooting Guide - Gasoline Fueled Engines
The troubleshooting guide that follows is designed to outline common problems, potential causes, and repair action related to
gasoline-fueled engines. This guide is applicable to both carbureted and fuel-injected engine, with the differences noted within
the chart.
Gasoline-Fueled Engine Troubleshooting Chart
Gasoline-Fueled Engine Troubleshooting Chart
Problem Potential Cause Action
No fuel in tank Fill tank with recommended fuel
Battery in poor condition or discharged Check for loose or corroded terminals,
broken wires, confirm that battery
voltage is between 12.2 and 13.5 volts
Perform On-Board Diagnostics
(OBD) test (EFI engines)
See applicable EFI Diagnostic and
Repair manual for your engine
Fuel shutoff valve closed or anti-afterfire
solenoid closed (carbureted engines)
Open shutoff valve or test anti-
afterfire solenoid for proper operation
Low fuel pressure (EFI engines) Verify that fuel pressure is between 38 - 41
PSI (262 - 296 kPa). See applicable EFI
Diagnostic and Repair manual for your engine
MAP sensor circuit intermittent
opens or shorts to ground
See applicable EFI Diagnostic and
Repair manual for your engine
Throttle Position Sensor (TPS) faulty
or throttle linkage to TPS sticking,
binding or worn (EFI engines)
See applicable EFI Diagnostic and
Repair manual for your engine
Intake Air Temperature
sensor faulty (EFI engines)
See applicable EFI Diagnostic and
Repair manual for your engine
Engine Control Module (ECM) failure to power up See applicable EFI Diagnostic and
Repair manual for your engine
Fuel line plugged or kinked Clean or replace fuel line
Fuel tank suction screen or fuel filter plugged Clean screen or replace fuel filter
Water in fuel tank Drain and clean fuel tank;
refill with recommended fuel
Weak or no voltage at spark plug See Check Ignition
Spark will not jump gap See Check Ignition
Engine flooded with fuel (carbureted engine) Open choke and close fuel tank valve or
disconnect anti-afterfire solenoid; then crank
engine until excess fuel is forced from exhaust
Choke partly open (carbureted engine) Close choke completely; if
necessary, adjust choke cable
Carburetor out of adjustment or clogged
Fuel injectors clogged
Service carburetor or fuel injection
system. See SECTION 6 - SERVICE
ENGINE SUBASSEMBLIES - Carburetor
Replace fuel injectors
Throttle closed Open throttle to FAST or RUN position;
check for binding throttle linkage
or disconnected governor linkage
Plugged exhaust ports Remove muffler and clean exhaust ports
Low or no compression See Check Compression Components
Carburetor or fuel system vent blocked Clean vent lines and ports
Worn or broken crankshaft/flywheel key Check flywheel and crankshaft key
for wear. See SECTION 6 - SERVICE
ENGINE SUBASSEMBLIES - Flywheel,
Crankshaft, Crankcase Cover
Faulty crankshaft position sensor Check crankshaft position sensor. See
Check Crankshaft Position Sensor
Faulty ignition coil Check ignition system. See Check Ignition
Engine is hard to start of fails to start
Improperly adjusted armature air gap Check armature air gap and adjust to proper
specification. See SECTION 8 -INSTALL
EXTERNAL ASSEMBLIES - Ignition Coil
Engine misfires under load Weak or irregular spark Check ignition system. See Check Ignition
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