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Old 06-29-2015, 08:57 PM
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flejter1
 
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There are a lot of good answers and theories here. The solenoid valves are important and needed like gunradd stated for starting purposes. The ECU commands the pump to start the fuel but it is the solenoids being controlled to pulse at a certain rate to allow small amount of fuel for ignition, then allow more for pre heat as well as the run valve will start pulsing with the start valve to regulate the fuel during pre heat and fuel ramp until it is running. I don't think a fuel pump can be controlled at such a small rate for starting purposes. The pump is pumping way more fuel than what is needed so the valves are restricting the amount supplied. Once it is running the "start solenoid" is shut off and the run solenoid is held full open with the ECU controlling the pump for full fuel delivery. The Solenoids are electro magnetic to open and they have a spring to return them closed when power is shut off to them. When you start most turbines, you hear the ticking of the valves opening & closing rapidly through the whole start process. You can manually start a propane version but even then you are opening and closing the propane valve (acting like a solenoid) to get the proper initial fire going. You don't just go wide open on the propane as it usually to much gas and won't ignite. As for a kero start version, good luck with manually trying to start that. Yes, the solenoid valves have many other benefits like many others here have stated.

Hope this helped,

Dirk