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post #6 of (permalink) Old 10-11-2002, 01:17 PM
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Re: engine question

Vapor lock is when the suction side of the pump lowers the pressure below atmospheric pressure and when combined with high temperatures, lowers the boiling point of the fuel. The fuel turns to a vapor in the line before the pump and the pump sucks vapor but no fuel. It's mostly a problem with the pump in the engine compartment, either electric or mechanical. If the pump is in the tank or next to it (below the fuel level) it shouldn't be a problem. The reason the return line solves vapor lock is it lets fuel continually flow through the system so it doesn't have time to 'stop' before the pump and warm and vaporize. It just depends on the routing of the fuel lines, heat sources and where the pump is.
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