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Fuel select valves |
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In twin-tank systems
where diesel fuel is used to start the engine and vegetable oil is used
when the vehicle is warm, one or more fuel selector valves are required to
manage which fuel is used at any given time. The valves can be
operated manually or electriacally via one or more switches. Temperature
sensors, timing devices and buzzers can be employed to automate the change
over to vegoil and the purge, helping to ensure that the warmup and purge
cycles are completed properly - safeguarding the engine's fuel
components
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As a bare minimum, a single 3 way fuel selector can be used to switch between the diesel and the vegetable oil fuel supply, with the return fuel from the engine being 'looped' back into the engine. This is not an ideal setup for a number of reasons
By using two 3 way fuel selector valves or a single 6 port selector valve the options are greatly increased. The fuel can be returned to the original tanks or the vegetable oil can be 'looped' with the diesel returned to it's tank. Pollak fuel selector valves are 6 or 3 port valves which switch the fuel feed and return lines simultaneously. They operate by using an electric motor to drive the valves into position. Being motor driven, they have high closing pressures (65psi) and are suitable for applications with in-tank fuel pumps. The valves are stable in either position, only drawing current for a fraction of a second while the position is transferred. They manage the switching of both the supply and return of fuel from the selected tank along with the fuel gauge switching if required. They are considered to be the best valves available for twin tank vegetable oil applications, as a result of their high specification, reliability and durability. Pollak Valves are available from BioTuning in the Online Shop . Pollak Valve fitting instructions can be downloaded from here Solenoid valves are electromagnetic 3 port selector valves that are used to switch between two fuel lines. They are driven such that the valve selects from one port when energised and from the other port when de-energised. Typically, they are rated to a lower fuel line pressure than the motorised valves and they only come in the three port version so 2 valves are required to manage the feed and return flows. There are a few options when it comes to acquiring solenoid valves for use with vehicle fuel systems. These included very cheap models which are not up to the task of switching between vegetable oil and diesel and have been known to fail. One of the more robust brands of three port solenoids are the Tecalemit models. These include a standard 12volt model with 4mm internal bore and a large bore version with 8mm internal bore in 12volt or 24 volt. These valves can also be picked up at the scrap yard or eBay etc. The large bore 12v version have been used in Jaguars and Daimlers for decades and have a strong British pedigree. Tecalemit Valves are available from BioTuning in the Online Shop . The Tecalemit Valve specification sheet can be viewed here In some twin tank conversions, a manual valve is used under the bonnet to purge any air that may be trapped in the fuel lines in a looped return system. These can be also be used for selection of the fuel lines and can either be located near the gear lever on the floor by the side of the driver or under the bonnet. These can either be domestic plumbing parts or dedicated fuel tank switches as those found in Landrovers for example. These parts are not easy to find cheaply. |
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Disclaimer
While every effort is taken to ensure that the information
on this site is accurate we accept no responsibility or liability for any
problems encountered while acting upon it.
