2016 YAMAHA YZ250F fuel pump

FUEL INJECTION SYSTEM
8-24
TIP
Disconnect the fuel pump coupler when this diagnostic tool is used. 6 Faulty ECU Execute the diagnostic mode.
(Code No. 30)
No spark  Replace the
ECU.
Fault code 39
Symptom Injector: open or short circuit detected.
Fail-safe systemUnable to start engine
Unable to drive vehicle
Diagnostic code No.36
ActuationActuates injector five times at one-second intervals.
“WARNING” on the Yamaha diagnostic tool blinks five times when
the injector is actuated.
ProcedureCheck that injector is actuated five times by listening for the oper-
ating sound.
Or-
derProbable cause of malfunc-
tion and checkMaintenance job Reinstatement method
1 Connection of injector cou-
pler.
Check the locking condition
of the coupler.
Disconnect the coupler, and
check the pins (for bent or
broken terminals and locking
condition of the pins).Improperly connected 
Connect the coupler secure-
ly, or repair/replace the wire
harness.After starting the engine, idle
this and wait about 5 sec-
onds.
Fault code No. is not dis-
played  Repair is finished.
Fault code No. is displayed 
Go to next order.
2 Defective injector. Check the injector.
“CHECKING THE FUEL IN-
JECTOR” on page 8-47.After starting the engine, idle
this and wait about 5 sec-
onds.
Fault code No. is not dis-
played  Repair is finished.
Fault code No. is displayed 
Go to next order.
3 Connection of wire harness
ECU coupler.
Check the locking condition
of the coupler.
Disconnect the coupler, and
check the pins (for bent or
broken terminals and locking
condition of the pins).Improperly connected 
Connect the coupler secure-
ly, or repair/replace the wire
harness.After starting the engine, idle
this and wait about 5 sec-
onds.
Fault code No. is not dis-
played  Repair is finished.
Fault code No. is displayed 
Go to next order. Fault code 33
SymptomIgnition coil: open or short circuit detected in the primary lead
of the ignition coil.

FUEL PUMP SYSTEM
8-32
EAS1SM9328
FUEL PUMP SYSTEM
EAS1SM9329CIRCUIT DIAGRAM
ONOFF
R O
OR
RRRRRRR
BBBBB
LLLB/LB/LB/LB/LB/LB/L
B/L
Gy
W
W
W
W
R
R
B
B
B
Y/B
Y/B
Y/W
Y/WB/YL/WB/R
B/Y
B/Y
B/W
R/B
R/B
B/R
B/R
G/WP/B
P/B
B/L
B/L
B/L
G/W
Br/W
Br/W
B/LB/L
B/W
SbP
Sb
Sb
P
P
P
L
L
LY
Y
B
B
LgGy
Lg
R
R
R
R
R
R
R
O
O
O
O
WWW W
W W
W WR B
B/LGyB Gy
BRRB
RLgB/W
B R
B/YB
B B
PY/BSbSbY/WP
BGy R
B/WB/LLYP/BG/WB/R
R/BLg
Br/W
P
O
B/YY/BSb
RR/B
RB/R
B/LBr/WB/L G/W
LYB/L
B/LP/BL
LLLRRRRRRR
BBB BB
B/L B/L B/L B/L B/L B/L

FUEL PUMP SYSTEM
8-33
2. AC magneto
3. Rectifier/regulator
4. Joint connector
5. Condenser
7. Engine stop switch
9. ECU (electronic control unit)
13.Fuel pump

FUEL PUMP SYSTEM
8-34
EAS1SM9330TROUBLESHOOTING
The fuel pump fails to operate.
TIP
Before troubleshooting, remove the following part(s):
1. Seat
2. Side cover (left/right)
3. Air scoop (left/right)
4. Fuel tank
5. Air filter case cover
1. Check the fuel pump system wire
harness connections.NG 
Reconnect.
OK 
2. Check the engine stop switch.
Refer to “CHECKING THE
SWITCHES” on page 8-38.NG 
Replace the engine stop switch.
OK 
3. Check fuel pressure.
Refer to “CHECKING THE FUEL
PRESSURE” on page 7-3.NG 
Replace the fuel pump.
OK 
4. Check the fuel pump system wire
harness.
Refer to “CIRCUIT DIAGRAM” on
page 8-32.NG 
Repair or replace the wire harness.
OK 
Replace the ECU.

FUEL PUMP SYSTEM
8-35

TROUBLESHOOTING
9-1
EAS1SM9348
TROUBLESHOOTING
EAS1SM9349GENERAL INFORMATION
TIP
The following guide for troubleshooting does
not cover all the possible causes of trouble. It
should be helpful, however, as a guide to basic
troubleshooting. Refer to the relative procedure
in this manual for checks, adjustments, and re-
placement of parts.
EAS1SM9350STARTING FAILURES
Engine
1. Cylinder and cylinder head
• Loose spark plug
• Loose cylinder head or cylinder
• Damaged cylinder head gasket
• Damaged cylinder gasket
• Worn or damaged cylinder
• Incorrect valve clearance
• Improperly sealed valve
• Incorrect valve-to-valve-seat contact
• Incorrect valve timing
• Faulty valve spring
• Seized valve
2. Piston and piston ring(s)
• Improperly installed piston ring
• Damaged, worn or fatigued piston ring
• Seized piston ring
• Seized or damaged piston
3. Air filter
• Improperly installed air filter
• Clogged air filter element
4. Crankcase and crankshaft
• Improperly assembled crankcase
• Seized crankshaft
Fuel system
1. Fuel tank
• Empty fuel tank
• Clogged fuel tank breather hose
• Deteriorated or contaminated fuel
• Clogged or damaged fuel hose
2. Fuel pump
• Faulty fuel pump
3. Throttle body
• Deteriorated or contaminated fuel
• Sucked-in airElectrical system
1. Spark plug
• Incorrect spark plug gap
• Incorrect spark plug heat range
• Fouled spark plug
• Worn or damaged electrode
• Worn or damaged insulator
2. Ignition coil
• Cracked or broken ignition coil body
• Broken or shorted primary or secondary
coils
3. Ignition system
• Faulty ECU
• Faulty crankshaft position sensor
• Broken generator rotor woodruff key
4. Switches and wiring
• Faulty ECU
• Faulty engine stop switch
• Broken or shorted wiring
• Faulty neutral switch
• Improperly grounded circuit
• Loose connections
EAS1SM9351INCORRECT ENGINE IDLING SPEED
Engine
1. Cylinder and cylinder head
• Incorrect valve clearance
• Damaged valve train components
2. Air filter
• Clogged air filter element
Fuel system
1. Throttle body
• Damaged or loose throttle body joint
• Improperly synchronized throttle bodies
• Improper throttle cable free play
• Flooded throttle body
Electrical system
1. Spark plug
• Incorrect spark plug gap
• Incorrect spark plug heat range
• Fouled spark plug
• Worn or damaged electrode
• Worn or damaged insulator
• Faulty spark plug cap
2. Ignition coil
• Broken or shorted primary or secondary
coils
• Cracked or broken ignition coil

TROUBLESHOOTING
9-2
3. Ignition system
• Faulty ECU
• Faulty crankshaft position sensor
• Broken generator rotor woodruff key
EAS1SM9352POOR MEDIUM-AND-HIGH-SPEED PER-
FORMANCE
Refer to “STARTING FAILURES” on page 9-1.
Engine
1. Air filter
• Clogged air filter element
Fuel system
1. Fuel pump
• Faulty fuel pump
2. Throttle body
• Defective throttle body
3. ECU
• Faulty ECU
EAS1SM9353SHIFTING IS DIFFICULT
Refer to “CLUTCH” on page 5-35.
EAS1SM9354SHIFT PEDAL DOES NOT MOVE
Engine
1. Shift shaft
• Bent shift shaft
2. Shift drum and shift forks
• Foreign object in a shift drum groove
• Seized shift fork
• Bent shift fork guide bar
3. Transmission
• Seized transmission gear
• Foreign object between transmission gears
• Improperly assembled transmission
EAS1SM9355JUMPS OUT OF GEAR
Engine
1. Shift shaft
• Incorrect shift pedal position
• Improperly returned stopper lever
2. Shift forks
• Worn shift fork
3. Shift drum
• Incorrect axial play
• Worn shift drum groove
4. Transmission
• Worn gear dog
EAS1SM9356CLUTCH SLIPS
Engine
1. Clutch
• Improperly assembled clutch
• Loose or fatigued clutch spring
• Worn friction plate
• Worn clutch plate
2. Engine oil
• Incorrect oil level
• Incorrect oil viscosity (low)
• Deteriorated oil
EAS1SM9357CLUTCH DRAGS
Engine
1. Clutch
• Unevenly tensioned clutch springs
• Warped pressure plate
• Bent clutch plate
• Swollen friction plate
• Bent clutch push rod
• Damaged clutch boss
• Burnt primary driven gear bushing
2. Engine oil
• Incorrect oil level
• Incorrect oil viscosity (high)
• Deteriorated oil
EAS1SM9358OVERHEATING
Engine
1. Cylinder head and piston
• Heavy carbon buildup
• Clogged coolant passages
2. Engine oil
• Incorrect oil level
• Incorrect oil viscosity
• Inferior oil quality
Cooling system
1. Coolant
• Low coolant level
2. Radiator
• Damaged or leaking radiator
• Faulty radiator cap
• Bent or damaged radiator fin
3. Water pump
• Damaged or faulty water pump
• Damaged hose
• Improperly connected hose
• Damaged pipe
• Improperly connected pipe

LIST OF SELF-DIAGNOSTIC AND FAIL-SAFE ACTIONS
9-6
*1: Symbols used in the explanations of the malfunction history
: Normal
: There is currently a malfunction or abnormal condition.
: A malfunction or abnormal condition occurred previously, but the affected system or component
is currently operating normally.
ACTUATOR OPERATION TABLE62 Malfunction history ( )
code No. erasure *1
• There is no history.
• There is some history.•00
• Other: Displays the total
number of ( ) and ( ).Replace all ( ) with ( )
by the operation start pro-
cessing.
64 Setting history display
• There is no history.
• There is some history.
• History is unknown (Histo-
ry data is damaged).Displays the presence or ab-
sence of the setting history by
Power Tuner.
•00
•01
•02—
65 Setting map erasure
• There is no setting.
• There is some setting.Displays the presence or ab-
sence of the setting history by
Power Tuner.
•00
•01Erase all setting maps by
the operation start process-
ing.
70 Program version number Displays a program version
No.—
Diag-
nostic
code
No.ITEM Actuation Procedure
30 Ignition coil Actuates the ignition coil five
times at one-second inter-
vals.
“WARNING” on the Yamaha
diagnostic tool blinks five
times when the ignition coil is
actuated.Check that a spark is gener-
ated five times.
• Connect an ignition
checker.
36 Injector Actuates the injector five
times at one-second inter-
vals.
“WARNING” on the Yamaha
diagnostic tool blinks five
times when the injector is ac-
tuated.TIP: Before performing
this operation, be sure to
disconnect the fuel pump
coupler.
Check that injector is actu-
ated five times by listening
for the operating sound. Diag-
nostic
code
No.ITEM Display Procedure