Service manual

G420F(FE) Service Manual Chapter 6. LPG FUEL DELIVERY SYSTEM 228
Figure 40. Opening the Service Tool Display
Idle Mixture Adjustment
NOTE : Be sure engine is fully warm (ECT>167°F
[75°C]) before performing the idle mixture
adjustment.
G420F LP Fuel Systems With O2 Sensor
Idle Adjustment
1. Install mixer and a UEGO or HEGO sensor. (A
UEGO sensor should be used when desired phi
settings are not at stoichiometric.)
2. After the mixer is installed, start and warm up the
engine to normal operating temperature
(ECT>167°F [75°C]). Also ensure that the vehicle
drive train and hydraulic systems are at normal
operating temperatures per vehicle manufacturer
recommendations.
3. Allow the engine to reach steady state at idle.
4. While monitoring the output of the UEGO or
HEGO sensor adjust the idle screw using a
standard screwdriver until the desired phi reading
is achieved (phi = 1.00 to 1.01 is optimal). To
make the mixture richer, turn the screw clockwise;
to make the mixture leaner, turn the screw
counter-clockwise.
5. Rev the engine to take it off of idle and let it return
to idle.
6. Once the engine has reached steady state at idle,
verify the phi reading. Adjust further as needed.
Power Valve Adjustment
1. The power valve should only be adjusted after the
idle screw has been adjusted properly. The
engine and vehicle drive train and hydraulics
should also be at normal operating temperatures.
2. Apply a load to the engine while the engine is
operating above idle speed. Torque converter stall
is the preferred operating mode for this test. If a
torque converter speed test cannot be performed,
the engine can be run at another speed (max
governor), but a load must be applied by using
hydraulics.
NOTE : While adjusting the power valve, do not hold
engine at load point for longer than 5-10 seconds.
Holding for a longer period of time will cause the fuel
temperature to drop, which could adversely affect
the power valve setting.
3. Monitor the output of the UEGO or HEGO sensor
while the engine is at the higher speed with the
load applied (phi = 1.00 to 1.05 is optimal).
4. If the phi reading is not at the desired level, bring
the engine back to idle and adjust the power valve.
5. Bring the engine back to the higher speed with a
load applied and verify the power valve setting.
Adjust further as needed.
6. Once the power valve is set, bring the engine
back to idle and verify the idle screw setting.
G420F LP Fuel Systems Without O2 Sensor
Idle Adjustment
1. After the mixer is installed, start and warm up the
engine to normal operating temperature
(ECT>167°F [75°C]). Also ensure that the vehicle
drive train and hydraulic systems are at normal
operating temperatures per vehicle manufacturer
recommendations.
2. Allow the engine to reach steady state at idle.
3. With the idle screw completely tightened
clockwise, use a standard screwdriver to adjust
the idle screw counterclockwise until a minimum
average MAP value has been reached. The MAP
value is displayed on the Service Tool screen.