No Purge System

As mentioned earlier, a patent pending no purge system is now available for most vehicles for use in warmer climates.  This consists of the “Cold Start Kit” which is a series of 12 volt heating elements fitted to the injector lines, coupled with a 16 or 32 amp fuel heater just before the injector pump.  

In a no purge system, the oil will stay in the injection pump, the lines feeding the injectors, and in the injectors themselves leaving the fuel components to deal with cold vegetable oil during the initial start-up phase. The main issue with operating on vegetable oil, is that the oil is very thick, and needs to be thinned to flow through the injectors so that it atomises properly.  

When starting on vegetable oil from cold, it is best to heat the fuel and fuel lines before starting,  About 2 minutes will allow sufficient time for the fuel to be heated to a reasonable temperature for the fuel system to cope.  Cycling the glow plugs a couple of times before starting will help heat the injectors from the base and improve the primary combustion in the cylinder .  

Although cycling the glow time may heat the oil a bit more thoroughly in the pre-combustion chamber, all fuel components will be subjected to higher stresses for a short time. Lucas injection pumps found in some diesel engines may be more prone to premature failure under these conditions.

You might find that there is an amount of exhaust soot on start up and the engine might run a bit lumpy for 10 to 15 seconds.  This is due to the inability of the injectors to properly atomise the fuel due to cold temperatures.  As the weather approaches cooler winter temperatures, it may be necessary to blend some diesel fuel with the vegetable oil to assist with starting.

Not using cold start heating systems or cycling the glow plugs may leave your engine vulnerable to serious damage such as sticking rings, cylinder wall glazing and piston seizures due to improperly atomised WVO hitting the cylinder walls for sustained periods.

A problem with some direct injection diesels running as a no-purge system on vegetable oil is ring land coking, which occurs when improperly atomised vegetable oil contacts the cold cylinder walls and is scraped off by the piston rings. The fuel will not vaporise like diesel and tends to char on the ring lands and cause the ring to jam in the groove.  

This condition can also be caused by conventional diesel fuel in engines with faulty glow plugs and or injectors, and is one of the reasons why most diesel engines make use of pre-combustion or swirl chambers. Many direct injection engines have a depression in the top of the piston to keep fuel from the cylinder walls, but it is best to check.

You might find that a single tank system with ‘Cold Start’ is certainly the easiest way to get started, as the basic system can be installed in less than a day for under $500, without specialist tools and equipment.  Other parts can then be added as your fuel savings grow, eventually arriving at a dual tank system if required.

I would still recommend a fuel processor and heat exchanger be placed in the fuel line to remove any water particles and assist with fuel heating.  You may require an electric pump either at the tank as a lift pump or after your fuel processor.

The no purge system does put considerable strain on your electrical system with an additional draw at start up of 24amps for a small engine and 30 amps for a larger one, which could draw up to 30amps while operating. 

If a no purge system is installed it is recommended to maintain a strong battery, and would be advantageous to upgrade the output of the alternator and or install a second battery.

I currently use an external car battery in the Tarago for the preheating of the fuel lines in the morning if we have forgotten to purge, as the single onboard battery sometimes can’t cope with the initial draw of the Cold Start system prior to cranking over.

Cycling the glow plugs may cause premature failure, so checking the condition of the glow plugs should be factored into your service regime.  It is important to ensure that the heaters are all working.  Checking the amperage draw at service or installing an amp meter will resolve this.

I have been operating the Nissan Patrol as a no purge system for months, without using a drop of diesel fuel.  As we originally set this vehicle up as a two tank system, I can now fill both tanks with 100% vegetable oil fuel, offering me a range of 1200km before having to refuel.  This allows me to drive anywhere in the State and back or between capital cities before having to refuel.