![]() ![]() While the atmosphere keeps the fuel in the tanks bubble-free, heating and the numerous bends in the lines and fittings create turbulence in the flow, the higher you climb the more likely the turbulence will create "vapor". Gasoline is sensitive to heat and pressure changes that along with the convoluted maze of tubing and fittings that the fuel has to travel through to get from the tanks to the engine is not ideal. The same thing happens when you hold your arm under water in the swimming pool and move it extremely fast, bubbles form in the area immediately behind your arm in the turbulent area. Decrease the pressure enough on a liquid and bubbles form. I did this on my Jeep and it works beautifully.A hydraulic pumping engineer described it to me and I will paraphrase a bit. Is no more "dead head" line pressure to overcome the carburetor needleĪnd seat.the pressure from heat bleeds off through the orifice and back to the tank. In addition, when the engine is shut off hot, there When fuel demand is low from the engine) to keep vapor lock at bay. Through the filter, and back to the "T" will keep the fuel cooler (even The constant small flow of fuel from the pump The line from the tank) but it won't bleed off all pressure while The fuel filter return port has an orifice restriction toĪllow just a little bit of fuel to return to the tank (or in this case, Plumb a line to connect the filter return port In the fuel line that comes from the tank to the fuel pump inlet, and Install the filter as close to the carb as possible, then install a "T" If one is notĬoncerned with originality, get a fuel filter from, Pump to the carb which makes them super sensitive to "hot soaking"Įspecially after shutting off the engine when hot. These Jeeps have a "dead-head" fuel supply from the Normally the fuel level in the bowl only needs to remain above the screen inside the bowl. Due to the “upside-down” nature of the bowl, it’s almost impossible to remove that last bit of air, but it hurts nothing. There will almost always be a bit of trapped air at the top of the bowl. I believe it also lowers the boiling point of the fuel. It reduces the amount of fuel in the pump and the line to the carb and in the carb and makes it take less heat to boil it. Air mixed with the fuel is not a good thing. If the bubbles enter around the outside of the chamber near the glass, the bowl gasket is leaking. If the bubbles enter the bowl from the fuel inlet near the bottom center of the bowl chamber, they are from air entering upstream, in the line or possibly the “shepherd’s crook” pickup in the tank. An indication of air leaking in is air bubbles in the glass bowl. These leaks often don’t leak fuel out, but do leak air in, especially if there is a restriction in the line upstream or in the tank pickup. ![]() When the clamp is used to squeeze the hose down tight, the hose can bunch up and leave wrinkles that leak. The hose clamped to a metal line is often not air-tight, especially if 5/16” hose is used on 1/4” line. The two most common things that I see that allow air to leak in are hose clamped to un-barbed metal lines and a loose pump bowl or bad gasket. The bowl is actually on the inlet side of the pump and the fuel is “sucked” through the bowl into the pump chamber. Another very common problem that gets blamed as vapor lock, and can actually contribute to vapor lock, is air leaks into the suction side of the fuel system, from the tank to and including the fuel bowl on the pump.
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