Fuel System Troubleshooting - Honda Nighthawk CB 750 1991 Service Manual

Fuel
System
3
Troubleshooting
Engine Won't Start
Too much fuel getting to the engine
-Air cleaner clogged
-Flooded carburetor
Intake air leak -
Fuel contaminatedldeteriorated
.
No fuel to carburetor
-Fuel strainer clogged
-Fuel tube clogged
-Fuel valve stuck
-Float level misadjusted
-Fuel tank breather hole clogged
Lean Mixture
.
Fuel jets clogged
Float valve faulty
Float level too low
Fuel line restricted
-
Carburetor air vent tube clogged
lntake air leak
Throttle valve faulty
-
Vacuum piston faulty
-
California Model Only: EVAP CAV control valve faulty
Rich Mixture
-
Bystarter valve in ON position
Float valve faulty
-
Float level too high
Air jets clogged .
Air cleaner contaminated
Flooded carburetor
Engine Stalls, Hard To Start. Rough Idling
Fuel line restricted .
Ignition malfunction
.
Fuel mixture too leanlrich .
Fuel contarninatedldeteriorated
-
lntake air leak
Idle speed misadjusted
.
Float level misadjusted
Fuel tank breather hole clogged
Pilot screw misadjusted
Slow circuit or bystarter circuit clogged
Emission control system malfunction
(California Model Only)
-EVAP CAV control valve faulty
-EVAP purge control valve
-loose, disconnected or deteriorated hoses of the emis-
sion control system
Afterburn When Engine Braking Is Used
Lean mixture in slow circuit
Emission control system malfunction
(California Model Only)
-pulse secondan/ air supply system faulty
-loose, disconnected or deteriorated hoses of the
emission control system
Afterburn Or Misfiring During Acceleration
.
Ignition system faulty
Fuel mixture too lean
Poor Performance (Driveability) And Poor Fuel Econ-
omy
.
Fuel system clogged
-
lgnition malfunction
-
Emission control system malfunction
(California Model Only)
-EVAP CAV control valve faulty
-loose, disconnected or deteriorated hoses of the
emission control system