Fig 7
The 2012 Chevrolet Express and GMC Savana 3500 and 4500 Cutaway Vans can now be equipped to operate on Liquefied Petroleum Gas (LPG). They include RPO K07 (Vehicle Fuel – Liquefied Petroleum Gas, Liquid) and RPO UFM( Parts Package – Complete Vehicle Kit, 3-Tank) or RPO UFP (Parts Package – Complete Vehicle Kit, 4-Tank).
Before the Vortec 6.0L V8 engine will start, vaporized LPG fuel in the fuel lines and injectors must be replaced with liquid fuel. A priming process is activated each time the ignition key is turned to ON. This can take eight or more seconds, depending on how long since the engine was last run. The LPG control module illuminates the Wait to Start indicator lamp on the center of the instrument panel during the purge cycle.
Liquefied Petroleum Gas
LPG, the same gas that is delivered to homes for domestic utility use, is mainly propane — a highly flammable, colorless gas. An odor additive enables detection by smell. Propane should never be smelled and a hissing sound should not be heard, except during refueling.
The fuel gauge has been calibrated to LPG pressure and will display full at approximately 36 gallons (136 L) for the 3-tank system and 58 gallons (220 L) for the 4-tank system. LPG quantity is affected by changes in fuel temperature and fuel pressure.
It is normal to hear the fuel flowing while the engine is running with the ears close to the pipes and other components. Do not confuse this with a hissing sound at fittings that may indicate a fuel leak.
The LPG system, including the tanks and tubing, has been designed to hold gas at a working pressure of 312.5 psi (2,154.6 kPa) and a burst pressure of 1,250 psi (8,618 kPa). It has also been tested for safety. Baffles are built into the tanks to keep the fuel pump submerged in liquid propane at all times.
LPG Tank Components
Fig 8
As an example of the LPG tank components, the front tank of 3-tank system (Fig. 8) includes:
1. LPG fuel bypass loop, mounted to a T-fitting on the return port of the fuel tank
2. Connection for the fuel return line from the distribution block
3. LPG cut-off solenoid, mounted to the outlet port of the fuel tank
4. Fuel level sensor
5. Liquid propane service valve and port
6. Manual shut-off for the liquid propane service valve (handle not included)
7. Spitter valve. Used for visual verification of 80% fill
8. LPG bypass loop solenoid and valve
9. Manual shut-off valve for LPG bypass loop
10. Fuel tank fill port and behind it, inside the tank is the 80% stop fill valve
11. Fuel tank electrical wiring harness pass-through for the internal fuel pump
12. Fuel tank access cover plate, for the internal components
13. Manual shut-off valve for the fuel return line
System Components
Fuel Tank Shields – The tank shields protect the LPG tanks. If a tank shield is removed for any reason, always reinstall it before operating the vehicle.
Overfilling Prevention Device – This device is a float-actuated valve that prevents the tank from being filled more than 80%, to allow room for expansion. A properly functioning OPD valve stops gas flow immediately when the mechanism closes.
Overflow Valves – Every inlet and outlet valve on the propane tanks has a built-in overflow valve. If propane tries to exit the system at a higher rate than a calibrated amount, the difference in pressure closes the overflow valve and restricts the flow with a 0.080 in. (2 mm) diameter orifice. Once the difference in pressure is equalized, the overflow valve will open.
Pressure Relief Valve – If the pressure in the fuel tank exceeds 312.5 psi (2,154.6 kPa), the valve vents propane vapor to the atmosphere. The pressure will not get this high unless the tank has been overfilled or unless the tank is hotter than 140°F (60°C).
Fuel Pump – The fuel pump is mounted inside of the fuel tank. The purpose of the fuel pump is to increase the line pressure of the liquid propane by 40-60 psi (275-414 kPa) over the internal tank pressure to ensure the propane is always maintained in a liquid state. To service the fuel pump, remove the fuel tank internal components access cover plate.
Fuel Injectors – Each fuel injector has a supply passage and a return passage. A passage between them is restricted by a cooling bushing. As liquid propane passes through the cooling bushing, pressure drops, the propane vaporizes and cooling occurs. This maintains the fuel in a liquid state, regardless of the outside temperature.
Fuel Transfer (4-tank model only) – On the 4-tank system, the main tank controls all fuel delivery to the fuel injectors. When the liquid propane control module senses a difference in fuel level between the tanks, the secondary supply valve opens and the secondary fuel pump operates. Liquid propane is pumped from the rear tanks into the main tank.
EVAP System – The conventional EVAP control system has been disabled, with the exception of the EVAP purge solenoid valve. All EVAP DTCs also have been turned off, so there is no scan tool support. A unique EVAP sub-system maintains compliant levels of evaporative emissions.
LPG Maintenance Schedule
The LPG engine is designed for routine maintenance (fluids, filters, etc.) similar to gasoline engine vehicles.
The LPG fuel system requires replacement of the LPG fuel fill filter and LPG in-line fuel filter every 30,000 miles (48,280 km).
- Thanks to Sherman Dixon and Chris Graham