G643(E) Service Manual Chapter 6. LPG FUEL DELIVERY SYSTEM 202
6. If present, set fuel select switch to LPG fuel.
When operated at the factory, it is critical to simulate
the airflow found on a forklift at idle as nearly as
possible in order to achieve the proper air valve lift
in the mixer. It may be necessary to place a load on
the engine to achieve the required airflow without
overspeeding the engine. Means of achieving this
load include:
a) Place an electrical load on the alternator. The
alternator should be able to briefly hold loads
of approximately 1.2 kW.
b) Attach the engine to a dynamometer.
Attach the Mototune Service Tool to the wiring
harness and add parameter MAFPort to the display
screen.
Factory Adjustment Procedure:
NOTE : Be sure engine is fully warm (ECT>167°F
[75°C]) before performing the idle mixture
adjustment.
1. Operating the engine on LPG fuel, start the
engine and permit the engine to warm up until the
coolant temperature (ECT on Mototune display) is
approximately 167°F (75 oC).
2. Set APP input to minimum.
3. Adjust the load until engine speed reaches 750
rpm.
4. Mototune display parameter LP Fuel Control must
display “Closed Loop.”
5. Use the Mototune Service Tool to monitor Duty
Cycle % on the Mototune display.
6. To adjust the idle mixture screw, use a 5mm hex
or Allen-type wrench. Turning the screw in
(clockwise) should increase the duty cycle; turning
the screw out (counter-clockwise) should
decrease the duty cycle.
7. Adjust the idle mixture screw on the mixer until a
reading of 40-45% is reached for the FTV Duty
Cycle in Closed Loop Idle (Figure 35).
Figure 41. FTV Duty Cycle Percentage Displayed on
Service Tool
8. Use the accelerator pedal to increase RPM above
idle momentarily (rev the engine) then release the
pedal to return to idle RPM. The duty cycle setting
should remain within the adjustment range (40-
45%). Place your thumb over the adjustment port
for a more accurate reading by preventing air from
leaking past the mixture adjustment screw, which
may cause the duty cycle to decrease.
9. Use the Mototune Service Tool to lock the FTV
duty cycle. Set display parameter
DitherValveDC_ovr = locked (displayed in screen
tab Manual Override 1 under AFR Trim Vales,
select “locked” under box labeled Lock DC%).
10. Use the Mototune Service Tool to monitor
throttle position (TPS1) and Exhaust gas oxygen
equivalence ratio (“O2 Value” in Figure 1). While
monitoring O2, slowly increase the pedal input
(APP) to achieve a TPS1 value of 15%.
11. Use the Mototune Service Tool to unlock the
FTV duty cycle. Set display parameter
DitherValveDC_ovr = unlocked (displayed in
screen tab Manual Override 1 under AFR Trim
Vales, select “unlocked” under box labeled Lock
DC%).
12. If at any time in step 10, O2 was greater than 1.2
go to step 13. If 02 remained below 1.2,
proceed to Step 15.
13. Adjust the idle mixture screw on the mixer until a
reading of 50-55% is reached for the FTV Duty
Cycle in Closed Loop Idle (Figure 35).
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