Fuel System Lean; Carburetor Malfunction - MerCruiser GM4 Service Manual

Fuel System Lean

1. Empty fuel tank
2. Fuel shut-off valve closed (if equipped)
3. Vapor lock
4. Automatic choke
5. Fuel tank vent plugged
6. Air leak on suction side of fuel system
7. Plugged or pinched fuel line
8. Fuel pump

Carburetor Malfunction

Symptoms
1. Flooding
2. Rough idle
3. Hesitation or acceleration flatness
Index
90-816462 2-695
Cause
Special Information
3. Engine will not start after warm engine shut down
4. Stuck open, wrong adjustment
5. Engine will start initially. After a short time of run-
ning, engine will stall and will not restart for a peri-
od of time. Can verify it is a vent problem by run-
ning engine with filler cap loose. Fill cap will act
as a vent.
6. Sucks air into fuel system reducing fuel volume
8. Low pump pressure
Cause
1. A. Needle and seat
B. Float adjustment
C. Saturated float
D. Gaskets leaking
E. Cracked fuel bowl
F. Fuel percolation
G. Automatic choke
2. A. Idle RPM too low
B. Idle mixture screws
C. Idle passages dirty
D. Throttle valves not closing
E. Engine flooding
F. Vacuum leak
G. Throttle body heat passages plugged
3. A. Accelerator pump
B. Leaking gaskets
C. Automatic choke
D. Power piston or power valve
E. Throttle valves
TROUBLESHOOTING - 1C- 15