FAQ Spotlight: Turbine Series Air Bubbles... A Real Problem?
This depends on the size of the air bubbles and the source of the air.
Small streams of "champagne" bubbles are probably just air coming out of fuel solution. At about 4"Hg vacuum, some air may begin to appear as small bubbles. A filter mounted 3 or 4 feet above the fuel tank and/or fuel passing through elbows and tee's creates low pressure zones where air and fuel separate. Air that is the result of low pressure is usually no concern, because the air is compressed back into solution at the injection pump.
Large "blobs" of bubbles that appear to come out of the "turbine" in the bowl must originate outside of the Turbine Series housing itself. The path from the inlet port to the bowl "turbine" is direct, and surrounded by fuel; so any air must be entering somewhere from fitting to the tank. (See illustration red arrow inlet flow path.) With the engine off, even the smallest fuel leak will eventually reveal itself as a wet spot. Fix these immediately. (Note: Never use pipe tape or dope on SAE O-ring fittings... this will cause, not prevent leaks.)
In the end, all fuel filters eventually plug, and if not changed, air and vapor will come out of the fuel, and the engine will stop. Best to change elements at 5 to 8"Hg above start point or risk an unscheduled complete loss of power.
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