Carburation to Gas LP

(Gas L.P. Traditional Systems)

The principle of carburation resides in take advantage of the physical forces. This is how the carburetor was designed which basic principle is to use atmospheric pressure and gaps created by it. The Gas L.P. is not pumped to the carburator, it passes through the carburator with the atmospheric pressure created by the need of fuel of the engine.

It is vital that carburator neck gaskets are in perfect conditions, because otherwise it might  be presented a leak of pressure affecting directly the proper functioning of the vehicle. 

The Gas L.P. contained in the tank is in liquid state in order to take advantage of a better storage. 

The liquid condition of Gas L.P. needs to be transformed into steam, which is done in a device called a regulator or vaporizer converter. The vaporizer has two receiving chambers where they prepare the fuel, called primary and secondary.

In the primary chamber the fuel will drop down its normal initial pressure in the tank at a pressure of 4 ½ to 6 lb, per square inch. To perform this operation it is necessary that it feeds on heat because when vaporization take place, it will be doing it with heat absortion, which, when is not enough it will result in  temperature drops, until  freeze. A vaporizer is necessary because on the contrary, it will cause difficulties especially to the engine start with cold cooling system and even more  in winter time, if not able to disperse the cold generated by vaporization.

In the secondary chamber: It is a great sensibility chamber which works  by pressure differences. With the vacuum caused by the carburetor, it lower the  internal pressure relative to the ambient and then a diaphragm is displaced by the higher external pressure, dragging a cam (secondary leads) which gives a secondary valve opening. 

Cruising Speed: 14:1 a 14.5 :1 vacío 12 a 15 pulgadas.

Power: 12,8: a 2 13.2: a vacío 3 a 5 pulgadas.

Lower: 12:1 a 13.2:1


We must clarify that although the gas analyzer is a reference that guide us, It is not establishing exact relationships of mixtures.  

There are two Gas carburetion systems to Gas L.P.: The mixed system, which may be used interchangeably with LP Gas or gasoline, and the total LPG in the mixed system. They are used as main components of the tank-filter valve (solenoid). The  LP Gas fuel solenoid, the switch, the adapter and the vaporizer can be used for extra protection on the safety valve. 

In all the LPG equipment, the same parts are used, except the gasoline solenoid.  Instead of  the adapter a carburetor is used. 

Before the installation of LPG equipment it is recommended to obtain the basic data of the engine, such as: displacement, maximum speed and type of carburetor installed, this in order to select the right equipment that includes the adapter or carburetor. 

To provide a better relation of air – fuel in all its operations. This point is very important because a bad calibration of the venturi will provide poor and rich mixtures at different stages of its work, with low performance in power, fuel consumption,  flashovers valves, pistons and carburetors. 

It is needed to have a plan for installation according to available space and not to start ing it without taking into consideration the following:  (Mixture with air recess is called "poor" and excess fuel is called "rich") .


The best place (when there is space), is in the inner bins provided at fixed locations, either directly, or through the use of brackets. 

The maximum distance recommended from the vaporizer to the carburetor, is 60 cm. A greater distance can cause reflection losses in engine operations. 

The place should be as fresh as possible and therefore avoid close hot spots, even with ventilation because when the engine stops, the heat irradiation increases damaging the components life. The height should be less than the water cooler for a complete filling of water by gravity and prevent air bags that prevent free circulation. 

The breathing  of the secondary diafragm  (the hole located at the bottom of the front cover), must not be placed in position that allows direct intake of air fan, hindering its operation. 

The vaporizer position must be always vertical, so that the vibration or shocks produced by the operations, won´t be transmitted to the internal mechanisms. It has to be considered a place that eases  and provides  an adequate maintenance environment. 


The solenoids must be installed in fresh places, making sure they have a good electrical ground for your optimal operation and that cables, both of power input and ground will not produce false contacts. 

Both fuel inputs are located on the oposite side of the brass connection (bodies). (solenoid position and inflated rubber). 


It is recommended to make the socket starting from the ignition switch to the coil before passing through the resistor. We insist that the given voltage for operation must be total and if we install 12 to 16 solenoids  there should be no voltage loss. They have been designed to open up with presssure of 17.5K per square cm. 1250lbs. per square inch and the most common failure is due to the low voltage operation. 


Gas L.P. is a fuel so noble that it tolerates any kind of operation even under adverse circumstances even though low performance issues will appear, as well as power loss,  flutter valve pistons and carburetors.

90% of the disadvantages attributed to LP Gas carburetion are due to low quality equipments or good equipments installed improperly. 

The hoses that attach the vaporizer along with the adapter that absorb vibration or movement without loosening screws or parts that become vents. 

It should leave a slight bend to absorb the changes in distance from the vibrational movements and securely fastened by means of clamps to the connections of the two parts. 


Tanks must be special made for carburetion and must have all its valves. Placing the tank in a place away from hot spots like engine exhaust. (double check valve tests). 


The vaporizer receives liquid fuel, then it converts it into steam to reduce its pressure and supply the  required amount by the engine to form a proper mixture. 

The capacity of the vaporizer is 400 M. The range starts from small engines of Cl 1-2 & up to engines of 900 cubic inch. 

Liquid LP gas  requires of a  feed temperature to become steam, this is easily accomplished with hot water provided by the engine, but before the engine water achieves a desirable temperature, it is required to have a scattering area with higher temperature , which is obtained in the water chamber of our vaporizer. 

We talk of course of water with antifreeze because water freezes at 0 ° Celsius. 


  • Lack of water in the radiator 
  • Very moldy water 
  • Imperfections in the operation of the water pump or a clogged conduit. 
  • Primary valve shabby and hence the vaporizer has excessive gas  that makes itself to freeze for not achieving the gas to evaporate.
  • Incorrect installation of the nozzle to a higher place than the radiator. 
  • Incorrect installation of the hoses. 

The vaporizer has inside of it neoprene and rubber parts that are removable.  Its duration is determined at the level of mercaptan containing LPG. Therefore it is impossible to know the length of them. 

To determine if diaphragms work, It is necessary to remove the cover of the vaporizer   (secondary),  if the diaphragm breaks when stretching  or it does not have elasticity then it has to be changed. 

Otherwise if is has its original elasticity then it´s convenient  to lubricate it with vaseline and put back in place. 

To improve performance of the vaporizer, place the gas duct already vaporized or the one that goes to the higher section of carburator. This is made not to block  this duct with  impurities and mercaptan

It is necessary to check every month inside the secondary chamber to find out if there are indications of mercaptans.  It is convenient to put a drain of carbon to drag out all the impurities. On the contrary the mercaptan will thicken drilling the diaphragms.

Vaporizer diaphragms as a form of precautionary tuning, must be removed at 8 or 10 months of normal operation.

If the vehicle is a forced work vehicle like a garbage truck, a gas tanker  or a delivery vehicle is necessary to change or lubricate the diaphragms from 4 to 6 months.

If this is not done the vaporizer will begin to send semi evaporated gas to the engine and it will begin to have effects as the flutter valve or piston drill and certainly excessive consumption of LPG

IMPCO has  three models of vaporizers. In a brief explanation may know its use .

MODELO “L”: It is the most used and commercial converter. It has a standard for all kinds of gasoline engines starting from a freight elevator  to high revolution engines or forced work vehicles. 

MODELO “E”: This model is used in turbocharged engines, fuel injection, natural gas equipment for stationary engines. In high displacement engines is  not convenient though if it can be used in low cubic capacity engines. Consumption would be excessive and with problems of flutter valves and pistons drilled. 

MODELO “J”: This model is usually used in forklifts and low cubic capacity Volkswagen engines, stationary engines etc. It is not suitable in high displacement engines  because the mixtures would be very poor and would cause overheating. 

MIXER 300ª

The main feature of this type of mixer is a vacuum chamber which works with a neoprene diaphragm resulting a differential pressure for optimum mixing. 

It has better advantages over all adapters – Venturi. 

The proof is that other brands have a similar mixer. 

Some of its many advantages is the return or discard of the leftover gas through the diaphragm,  this is very important because with a explosion in false with excess gas  and an adapter system – Venturi can cause flaming in the carburetor and in the 300A is almost zero although the flaming in the carburetor can be caused by other types of problems.