Alpga Technical information

June 1994

Convertor LP gas filter lock mounting
A recent vehicle accident between a Ford utility and a Ford taxi resulted in one of the vehicles
burning due to fire being started by an electrical spark igniting the escaping LP Gas.The taxi suffered major panel damage at the front near side area. The LP Gas lock off was fitted adjacent
to the headlight assembly. The LP Gas lock off was fitted into the back of the convertor with no support bracket.When the lock off is fitted this way and in this position,it becomes vulnerable to accident damage.

Due to the accident and the poor positioning of the lock off, an LP Gas liquid leakage occurred which was ignited by a spark created by a grounded live 12v wire running to the headlight.

The excess flow valve operated as designed but a major fire still occurred due to the liquid escaping
from the service line. Fortunately, the driver and passengers managed to escape the burning vehicle.

AS 1425 and in particular clause 3.9.7 requires the LP Gas lock off "shall be located so as to be
reasonably protected from impact in a collision".
Screwing a lock off into a convertor , then not
supporting it with a bracket and placing the convertor/lock off assembly behind a headlight is not
protecting it from impact damage in a collision.

The LP Gas lock off is the last line of defence against escaping LP Gas liquid in the underbonnet
area. Consequently, care should be taken with where it is fitted. Even with an electric shut off at the
cylinder, there is enough fuel in a service line to create a dangerous situation.

LP Gas Lock off operation
AS 1425 clause 2.17 states that prior to an LP GAS lock off opening , two conditions must be met

  1. The ignition is on.
  2. The engine is turning.

It also states that the LP Gas lock off "may be permitted to open for a period of up to three seconds when the ignition is first turned on so as to allow priming of the fuel system".

Some installers are not fitting a conventional electronic or vacuum control for the LP gas lock offs
to meet Standards requirements but are using the OEM vehicle's Electronic Fuel Management computer control of the fuel pump circuitry to control the LP Gas lock off operation.

There are some fuel injected vehicles which have petrol fuel pump electronic controls that would satisfy clause 2.17. However ,there are others that allow priming of the fuel system but when the engine is turned off they allow the petrol fuel pump circuit to be still energised for one to ten seconds . This is particularly evident when the engine oil is cold or some non original engine oil filter is fitted.

When this situation occurs it is contrary to AS 1425 requirements and can lead to a quite dangerous situation.

An installer must be familiar with the operation of the Electronic Fuel Management system of the vehicle he is converting prior to making a decision on the method he is going to use to control the operation of the LP Gas lock off.

If you are not sure , the safest option is to fit an electronic LP Gas controller that meets AS 1425 requirements.

This information was supplied to courtesy of the Australian Liquid Petroleum Gas Association