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Looses prime i have replaced all the hoses and primer button and replaced the diaphrahms in the carburator. but i still hear air when i pump the primer bulb. any other ideas ??
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need to clarify your statements
you say-- have replaced flexible lines from the tank to the engine --replaced the primer bulb
well that is all the rubber hoses from the tank to the pump on the engine
Then you further state only parts not replaced are the connections between the
gas tank and the motor and the tank itself
Well that connection is the rubber hoses that you stated were already replaced
So this may help rubber in outboard motors rots internally so replace all rubber from the tank to the motor, overhaul the fuel pump on the motor and all the rubber hoses from the pump to the carby/s
the primer bulb will not pump fuel if the tank vent is not open so that is one reason you feel like it is pumping air when priming
best advice is --no e-mix fuels to used on out board engines
Do not mix them up!! Doing so will bring debris into carburetor. Assuming the line from back of tank to carburetor is the fuel feed line then you should also plan to replace it if the other lines have failed..
The primer bulb sucks (pulls) the air fuel through the carburetor thus venting out any air. The process draws the fuel through the in tank filter through the impulse fuel pump. The fuel connects via an internal carburetor passage from the pump to the needle valve and during the prime passes the needle valve into the pressure diaphragm chamber. From there the fuel is drawn(sucked) into the inlet side of the purge/prime valve and returns the air fuel into the tank.
The center hose on the primer is the return into the fuel tank. The hose from the center of the primer bulb goes directly to the fuel tank and is the return. The outer diameter hose connection to the primer is the connection made to the carburetor. By closing off the end of the hose you can test with your finger the function of each hose. You do not want to pass fuel into the carburetor by reversing the primer hoses.
it still needs priming all the way down to the foot valve
try putting a hose fitting in the primer hole and with a good water supply ( tank, garden hose ) turned on run the pump until you get a good supply the turn of the primer hose
if you have an air leak the pump will stop pumping after a few seconds as it sucks in the air and the prime is lost
could indicate that there is no water at the foot valve
Does the engine run fine after it starts? Most common problem with primer bulb losing prime is an air leak in the fuel line or primer bulb. Air leaks don't always leak fuel. If there is an air leak between the primer bulb and gas tank there is no pressure, only vacuum. If it is not a major leak it might not leak without pressure but it will allow air to enter the fuel line. If it is a very minor air leak it could allow air to replace the liquid in the fuel line over time, but so little air once it is primer again that the fuel pump can over come it with volume of fuel.
Primer bulbs do not stay firm, as they are when initially pumped up, after the engine is running. There are check valves in the primer bulb that hold pressure in the primer bulb and throughout the fuel line to the engine. Once the engine starts the fuel pump creates vacuum drawing fuel into the engine diminishing this pressure and releasing the check valves. At this point the primer bulb is just another segment of fuel hose allowing fuel to pass through it as the fuel pump demands. The primer bulb functions much better when the outlet side is higher than the inlet side. This position makes it easier for the check valves in the primer bulb to seat and release as needed. If the primer bulb is functioning properly and is positioned with the outlet side higher than the inlet it should not be necessary to cover the end of the fuel hose with your thumb to get it to prime.
If the engine is hard to start after being fully primed there could be a problem with the fuel system on the engine. Some engines are hard to prime once air has entered the system, especially fuel injected models.
Check to be sure there isn't a small hole or crack in the priming bulb. If there is it allows air to enter fuel line, loosing the prime. Most have a collar that unscrews to remove it.
The hoses run through a hole into the gas tank, they are fitted with a filter inside the tank. Drain the tank, and manipulate the hose end to where you can grab it throught he filler hole, Remove the filter, run new gas lines into the tank and through the filler hole to replace the filter, reattach to the carburator. The primer bulb should have 4 small screws attaching it to the carburator. Remove the screws, place in new primer bulb, and you should be back to trimming asap.
get a container with fuel(about 4 liters will do). put a hose from the Primer to the fuel container and another hose from the injection pump return line to the container. if it works fine then the air leak is between the tank and the primer.
If it's coming from the primer bulb, replace the bulb. If it's running out the carburator, take iff the air filter and check for obstructions. 2 - 3 pumps is all it should need.
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