Insufficient Power Output - Toyota 4Y 2006 Manual

INSUFFICIENT POWER OUTPUT (INCLUDING HUNTING)
1
Classification
Ignition
Fuel
Main places for inspection and adjustment
1. Ignition timing [Point 21
2. Vacuum advancer
3. Ignition circuit
4. Governor controller
5. Vacuum pipe
6. Vacuum controller
7. Breaker plate
1. Air governor [Point 31
2. Carburetor
3. VCV inside air governer
Compression
1. Valve
2. Piston rings
3. Piston
14. Cylinder
I
[Point I]
Inspect the relief down speed
This is a test to see whether the lack of power output is on the engine side or on the drivetrain system side. If the
relief down engine speed is within the standard values, then the engine is normal and the drivetrain system needs to
be checked.
Drivetrain [Point I]
Note:
If the ignition timing is retarded, the engine speed will become slower during a torque converter stall test.
Do not mistake this for a reduction in stall speed (only torque converter vehicles).
1. Slipping of the clutch
2. Slipping of the torque converter one-way clutch
(torque converter models only)
[Point 21
Generally if the ignition timing is retarded excessively, the vehicle after-fires, and tends to overheat easily. If the
ignition timing is advanced excessively, this tends to cause knocking and loss of power. With forklifts in particular, the
construction makes knocking unlikely to occur (the drive gear ratio is large), and therefore it becomes difficult to
recognise fault phenomena indicative of advanced timing.
[Point 31
Adjust the air governor
If the relief down engine speed is faster than standard, or if the engine starts hunting, adjust the air governor. If power
output does not improve (the relief down is large) even after adjusting the air governor, the fault is in the governor
itself, or in the fuel system, ignition system, or compression system.