The highest air temperatures during a ‘heat soak’ will occur 30-40 minutes after the engine is shut off and can stay at that peak for up to 1-1/2 hours. Normally, the quieter the engine compartment is, the hotter the air tempera ture will be on the inside during the ‘heat soak’. This is because there is no air movement inside the compartment and no coolant flow through the engine. The air temperature inside the engine compartment during a ‘heat soak’ will rise higher than during the engine’s ‘running time’. This period of time is called the ‘heat soak’ time. This can cause high air temperature inside the engine compartment while the engine is operating and for a period of time after it is shut off. This is done by using an insulation material and by making ‘engine covers’ tighter. Over the last several years, engine compartments have been designed to be quieter. Fuels purchased in most areas of the USA from late September through early April will cause most of the problems.Ī. Refilling the boat’s fuel tank with lower RVP fuel will decrease the chance of vapor locking. 11 to 15 RVP (cool to cold weather) fuel will change from liquid to a vapor at lower fuel temperature than 8 to 10 RVP (warm to hot weather) fuel will. Find out what the RVP of the fuel in the boat’s fuel tank is. Fuels containing alcohol are more likely to vapor lock on hot days.ī. Find out what type of fuel is in the boat’s fuel tank. If these more common problems are not causing the complaint, then continue.Ī.
#Small engine vapor lock portable#
Use a portable outboard fuel tank con nected directly to the engine’s fuel inlet fitting as a quick way to test the system.
Include the brass fitting threaded into the engine’s inlet in this test. Always use a wrench to hold a brass fitting that is threaded into an alumi num casting when tightening another fitting threaded into it to prevent the casting from cracking.Ĭheck the complete fuel supply system of the boat for a fuel restriction. Often systems will leak air but not fuel. Pressurize the fuel system that goes to the en gine to 8 psi (55 kPa) with a hand pump to see if it holds this pressure. IMPORTANT: Do not pressurize the boat’s fuel tank(s) in this test.ĭisconnect the fuel line from fuel tank(s).
#Small engine vapor lock cracked#
Check for a cracked housing where a brass fuel fitting is threaded in it. Check the tightness of all fuel fittings and clamps. The outside air temperature on the day the boat is being operated.Ĭorrections That Can Be Done To Help Minimize Vapor Lockingīefore looking at the customer’s problem as a vapor locking condition, make sure some thing else is not causing the running problem.Īir leak in the engine or boat fuel system.How quickly the engine is shut off after running at cruising or higher rpms and how long the engine and engine compartment are allowed to cool off after use.Extra fuel filters, fuel manifolds, anti-siphon valves, shut off valves, tank selector valves and the number of 90 degree fittings used. This includes Inside Diameter (ID) of fuel line and fittings, fuel line length, routing, bends or kinks and the clamps that secure it. Temperature and vacuum on the fuel that is being delivered to the engine.Engine compartment air temperature and its ventilation system.‘Win ter grade’ fuels sold from October through March in most areas have the highest RVP. Type, formulation and RVP of the gasoline in the boat’s fuel tank or sold in the area.These con ditions include but are not limited to: It will normally take several following conditions to make an engine ‘vapor lock’. NOTE: The new ‘Reformulated’ fuels have the RVP (Reid Vapor Pressure) very carefully controlled. Fuels containing alcohol and ‘winter grade’ fuels will cause vapor locking complaints to increase.
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