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Tan, MerCruiser Certified Technician
Category: Boat
Satisfied Customers: 10894
Experience:  40 yrs. experience with complete engine repairs both inboard/outboard and MerCruiser Certified Technician.
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I have a Perkins 4-108 and I keep getting air in the fuel lines

Customer Question

I have a Perkins 4-108 and I keep getting air in the fuel lines after engine shuts down and sits over night. I bleed the system then it will start up again and run like a top. I have checked all connections but wonder if it is a problem with the return fuel line somehow. Fuel tank is below engine. I have heard that Bermuda 40s used to have this problem chronically with Perkins but can't understand why. Thanks. Peter from Marblehead
Submitted: 2 years ago.
Category: Boat
Expert:  Tan replied 2 years ago.
Hello Peter. My name is***** is due to the check valves in the lift pump they are not seating completely and the fuel is siphoning back into the fuel tank. You can install a anti siphon valve in the fuel line where it connects the the fuel tank or install a shut off valve at the same location. Turn the fuel off when you aren't using the engine. The anti siphon valve has a check ball that closes when the engine isn't running keeping the fuel from siphoning back into the fuel tank. click here Does this make sense?

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