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Old 10 June 2007, 06:14   #1
Country: UK - England
Town: Bristol
Length: 5m +
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Posts: 338
Fuel Priming Question

Does anyone know whether this is a problem or normal?

In the past, when squeezing the priming bulb on the fuel line, on several outboards I keep squeezing until it is rock hard.

Yesterday, I noticed, because the engine cover was off, that once the bulb was hard if I continued to squeeze it, I was getting fuel coming out of the carbs through the air intakes. The engine was actually tilted up a bit so the air inlets were lower than the cylinders.

Part of me thinks that the carb floats should close off and prevent any fuel coming out.....or am I just 'beating' the float holding pressure with extra hard squeezes?

I stripped all three carbs, cleaned and rebuilt them but it still did it.

So, is this OK or do I have a serious problem?



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Old 10 June 2007, 17:28   #2
Country: UK - Scotland
Make: Ribcraft
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I guess it depends how hard you were squeezing the primer. They normally seal pretty well but remember their main purpose is to stop fuel against the pressure of the normal engine fuel pump. You don't mention what engine this is on but I assume the fuel pump is on one of the carbs / manifold.

I normally pump the primer until it's just hard and nothing leaks but I suspect if I kept pumping I'd see fuel flowing out!

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Old 10 June 2007, 17:31   #3
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Originally Posted by Orville View Post
am I just 'beating' the float holding pressure with extra hard squeezes?

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Old 11 June 2007, 06:08   #4
Country: UK - England
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Engine: johnson 175
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You don't want to pump the primer bulb untill it is rock hard this can cause fuel pump diaphragms to rupture which cause fuel leaks and shut downs.
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