Mi-04 Lp Fuel Filter; Fuel Lock-Off (Electric) - Daewoo G420E Service Manual

MI-04 LP Fuel Filter

Figure 11
After exiting the fuel tank, liquid propane passes
through a serviceable inline fuel filter to the electric
fuel lock off. (Figure 11) shows a typical inline type LP
fuel filter manufactured by Century. The primary
function of the fuel filter is to remove particles and
sediments that have found their way into the tank.
The LP fuel filter will not remove heavy end solids
and paraffin's that build up in LPG fuel systems as a
result of vaporization.
Tier
G420E/G424E LP Engine
MI-04 Fuel Lock-Off (Electric)
Figure 12
The fuel lock-off is a safety shutoff valve, normally
held closed by spring pressure, which is operated by
an electric solenoid and prevents fuel flow to the
regulator/converter when the engine is not in
operation. This is the first of three safety locks in the
MI-04 system. (Figure 12) shows the electric fuel lock
assembly.
In the MI-04 design, power is supplied to the fuel
lock-off with the SECM controlling the lock-off ground
(earth) connection. The lock-off remains in a normally
closed (NC) position until the key switch is activated,
this supplies power to the lock-off and the SECM but
will not open the lock-off until the SECM provides the
lock-off ground connection. This design gives the
SECM full control of the lock-off while providing
additional safety by closing the fuel lock-off in the
unlikely event of a power failure, wiring failure or
module failure.
When the liquid service valve in the fuel container is
opened liquid propane flows through the LP filter and
through the service line to the fuel lock-off. Liquid
propane enters the lock-off through the ¼" NPT liquid
inlet port and stops with the lock-off in the normally
closed position. When the engine is cranked over the
main power relay applies power to the lock-off and
the SECM provides the lock-off ground causing
current to flow through the windings of the solenoid
creating a magnetic field. The strength of this
magnetic field is sufficient to lift the lock-off valve off
of its seat against spring pressure. When the valve is
open liquid propane, at tank pressure, flows through
the lock-off outlet to the pressure regulator/converter.
A stall safety shutoff feature is built into the SECM to
close the lock-off in case of a stall condition. The
SECM monitors three engine states. Crank, when the
VR sensor detects any engine revolutions. Stall, when
the key is in the ON position but the VR sensor
detects no engine revolutions, and the Run state,
when the engine reaches pre-idle RPM. When an
operator turns on the key switch the lock-off is
opened but if the operator fails to crank the engine,
the SECM will close the lock-off after 5 seconds.
17 System Operational Overview