Liquefied petroleum gas (LPG) is extracted from natural gas or derived as a by-product of the petroleum refining process. It actually describes a whole group of products consisting of one or a mixture of the hydrocarbons propane, propylene, butane and butylene. In Australia, two grades of LPG are commonly used:

The LPG you use for your BBQ or other appliances is propane only. Car LPG is a blend of mainly propane and butane.The two types aren’t interchangeable. It’s stored under pressure as a liquid. When the pressure is reduced (for example, for combustion), the liquid turns into gas and expands to about 270 times the liquid volume.
 
This means LPG is very convenient to transport and store. The gas is heavier than air and very explosive. LPG therefore contains a strong odorant (‘rotting cabbage’), so you’re quickly aware of any leaks.

Source: Choice Sep 06
Maintenance of LPG and Duel fuel vehicles

Apart from general vehicle maintenance LPG has some other needs for engine protection. LPG has less deposit and will keep the oil cleaner than petrol. Even though the oil looks clean it may be contaminated with acids. However, Sutherland Shire LPG Centre can alleviated this problem with regular servicing and oil changing, at recommended periods.

Regular safety checks
 
A safety check can be carried out as part of the maintenance schedule, at rego time or at any time the owner wishes. Typically checked items are:

The LPG tank is Protected from heat sources, loads, and the ground clearances and road objects
 
Tank service valve operation designed to close off the gas line at the gas tank if the engine stalls or the ignition is switched off has no gas leaks and is not subject to any manufacturer recalls

Lines and connections are protected from heat sources and are in good condition

Gas locks, mixers and converters are secure

Gas locks close off fuel supply if engine stalls or if the ignition is switched off

The wiring is neat and tidy, and secured to avoid shorting of sparking

That there are no exposed electrical terminals

Heat shields are in place to protect gas components subject to tank pressure

Ignition Check - Ignition quality is critical for successful LPG operation as in most systems a miss fire will almost always cause a backfire. Backfires can cause a car to stall, or hesitate in an intersection. It can damage air induction components and air filter boxes, and can even cause engine damage

Leads for continuity and for insulation breakdown, especially at spark plug boots

Coils for output voltages
 
Spark plugs for age or fouling

Timing suitable for LPG or petrol operation

Mixture Check - Newer systems are computer controlled and mixture checks usually involve using specialized test equipment suited to the brand of gas system being serviced. Sutherland Shire LPG Centre has laptops and hand held computers dedicated for servicing these systems.

Adjustments are commonly needed on some brands to allow the computer to have control in its operational range. Blocked air filters can also have detrimental effects on mixtures but, depending on the gas system, the computer can compensate for the increased mixer signal for a little while.

Converter Service - Converters receive the LPG in a high pressure liquid form and output to the engine a low pressure vapour. Any oil or waxy contaminates that are in the LPG fuel will stay dissolved in the liquid phase, bypassing any filters. and end up collecting in the gas converter as the LPG is drawn off as a vapour.

These heavy ends (longer molecule chains) look like oil or a light wax, and can damage the converter diaphragm by causing stiffening, softening, perforation of the diaphragm or lean against the diaphragm and cause incorrect operation. Also, with heat, sometimes these oily residues can carbonize, and become small particles that block idle jets and passageways.

A converter service is recommended at 20,000 kms on average. It usually involves draining the oily residues (best done when the converter is hot), and cleaning any removable jets, but sometimes my involve an overhaul kit or a new gas converter.

Gas lock and Vapour filters. Gas locks must always have a filter in line before the valve seat, so that no contaminate can cause the seat to leak when closed off. These filters need to be changed at service intervals specified by the installer of manufacturer. On gas injection systems, the gas injectors can be effected by contaminates so there is a vapour filter fitted between the vaporiser-regulator and the injector rail. These should be replaced at service intervals.

Sutherland Shire LPG Centre, located in the Caltex Workshop at 56 North West Arm Road, Gymea (Cnr Avenal Road) can carry out all these checks, repairs and conversions/installations on new systems.
 
Just phone David or James
on 9545 6809 or 0411 33 0005