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DESCRIPTION AND OPERATION OF THE FUEL
SYSTEMS
LPG FUEL SYSTEM
The primary components of the LPG fuel system
are the fuel storage tank, regulator, throttle control
device, fuel injectors, engine control module (ECM),
catalytic converter and Heated Exhaust Gas Oxy-
gen (HEGO) Sensor.
LPG FUEL TANK
LPG is stored in the fuel tank as a liquid. The ap-
proximate pressure of the fuel in the tank is 16.5
bar (240 psi) when the tank is full at an ambient
temperature of 27° C (81°F). The boiling point,
(temperature at which the liquid fuel becomes va-
por) is approximately -40° C (-40° F). When the
fuel changes from liquid to vapor the fuel expands
and creates pressure inside the tank. When the
tank service valve is opened the pressure inside
the tank forces the liquid fuel out though the pickup
tube located near the bottom of the fuel cylinder.
The service valve mounted in the end of the cylind-
er controls the flow of fuel from the tank. By turning
the handle to its “open” position, fuel flows out of
the tank and into the service line. The service
valve is also equipped with a safety feature called
an excess flow check valve. This feature reduces
the flow from the service valve in the event of a rup-
ture of the fuel line or any downstream fuel
transport components. A safety valve is built into
the tank. Normally set at 25.8 bar (375 psi), it will
release pressure to prevent tank rupture due to
over-pressurization of the cylinder
Typical LPG Cylinder
1. Liquid Outage Fill Check Valve
2. Pressure Relief Valve
3. Liquid Outage valve w/quick disconnect coupl-
ing
4. Filler Valve
5. Fuel Gauge
6. Vapor Withdrawal Tube (when applicable)
7. 80% Limiter Tube
8. Fuel Level Float
9. Liquid Withdrawal Tube
SERVICE LINE
LPG flows from the fuel tank to the Regulator via
the service line connected to the tank utilizing a
quick coupler. The other end of the service line is
connected to a bulkhead connector, allowing for a
safe means of passing through the sheet metal
and into the engine compartment. The service
line is made of high pressure hose with special
material or possibly tubing which is compatible
with the LPG fuel and should always be replaced
with an OEM supplied part.
The bulkhead assembly should never be
removed. Never run a service line through
the sheet metal.
FUEL FILTER
LPG, fuel like all other motor fuels is subject to
contamination from outside sources. Refueling of
the equipment tank and removal of the tank from
the equipment can inadvertently introduce dirt,
rust and other foreign matter into the fuel system.
It is therefore necessary to filter the fuel prior to
entering the fuel system components downstream
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