Landoll Bendi B40i4, Maintenance Manual

Page: 123 / 142

ENGINE WITH FUEL SYSTEM
5-3
2.4L LPG Engine System Operation
The manufacturer of record for the 2.4L engine, fuel and
emissions system is GFI. The key components of the
2.4L engine system are the propane vaporizer, the
electronic throttle, the engine control unit (ECU), the
injector driver module, the fuel rail, the propane injectors,
the oxygen sensor and the catalytic converter. The
system operation, which operates on a torque based
control strategy, is summarized as follows:
Propane
LPG is stored in the fuel storage cylinder in liquid form at
pressures ranging from 25 to 300 psig (depending on the
ambient temperature). When liquid propane changes
from a liquid to a vapor, it expands 270 times. Heat and a
drop in pressure, supplied by the engine coolant and the
fuel vaporizer, are required to change the propane from
the liquid form to a vapor. The fuel storage cylinders used
for this application are designed to deliver liquid fuel,
unlike a cooking cylinder that is designed to deliver
vapor.
LPG Tank Valve
The valve opens and liquid propane flows from the fuel
storage cylinder to the vaporizer through an integral
liquid fuel filter.
Fuel Shutoff Solenoid
This solenoid is a normally closed valve on the vaporizer,
controlled by the engine ECU, allows the fuel to flow into
the vaporizer when the ignition key is turned on and the
engine is running. The fuel shutoff solenoid is also
opened momentarily (for 2 seconds) when the ignition is
first turned on to allow the system to pressurize even if
the engine is not started.
Vaporizer
When the fuel shutoff solenoid (1) on the vaporizer is
open, liquid propane flows into the vaporizer (B) where
the pressure is reduced to approximately 88 kPa (12.6
psi) and heat from the engine coolant (D) are used to
convert the liquid fuel to gas (A). The regulator
mechanism in the vaporizer provides the gaseous
propane at a consistent operating pressure of 88 kPa
(12.6 psi), referenced to the manifold pressure, to the fuel
rail and gaseous fuel injectors. By referencing the outlet
fuel pressure to manifold pressure, the injectors can have
a longer pulse widths at idle (low MAP, hence low fuel
pressure) which results in a more stable idle and also
supply the required maximum flow at full load (high MAP,
hence high fuel pressure).
Figure 5-1: Vaporizer
Figure 5-2: Vaporizer Pressure Regulation