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-   -   Dissappearing Fuel (http://www.rib.net/forum/f8/dissappearing-fuel-56856.html)

cgf10 25 July 2013 19:02

Dissappearing Fuel
I have a Yamaha 100hp 4 stroke. Its a great engine but this year I seem to have a strange new problem to solve. The fuel seems to be dropping out of the fuel line and requires pumping with the primer bulb for every single cold\first start of the day. Once started the boat seems perfectly ok to start throughout the day but if I come back the next day I have to reprime the bulb and find the fuel line appears to be totally empty. Anyone else had this issue ?

Nos4r2 25 July 2013 19:55

You've got a minor air leak in the fuel line somewhere. It might even be at the bulb. Check the connections.

You won't necessarily see a fuel leak from it if it's a tiny leak.

cgf10 26 July 2013 02:51

Nos - thanks, in that case I think I know exactly where this is. The gasket between the fuel sender unit and fuel tank has expanded and no longer makes a perfect
seal. I've ordered a new one already so hopefully that will be my problem solved.

Nos4r2 26 July 2013 04:13

I suspect it's not that gasket-unless Ribeye use some very unusual ( and extremely complex) tanks. It's more likely you just need to nip up or reseat a jubilee clip or change the primer bulb. It shouldn't be any drama to sort out.

boristhebold 26 July 2013 05:23

Im slightly confused, I thought it was normal practice to pump the fuel bulb at the start of each days of boating. I have a 200HP Yamaha and always pump the bulb each day I use it.

Nos4r2 26 July 2013 05:39

You shouldn't have to do it for every cold start. You probably don't need to pump it Boris. I don't have to on either boat as long as the fuel line isn't disconnected or a tank runs out.

The way I read the OP's question is that if he doesnt pump, it has to draw fuel all the way from the tank and takes ages to fire up.

vjmehra 26 July 2013 07:51

We have to pump every cold start, but then we have portable tanks and disconnect the fuel hose every time. So maybe that is the difference?

Festinghouse 26 July 2013 08:10

replace the primer bulb, this has a built in one way valve which often fails allowing fuel to siphon back to the tank. be careful as some bulbs need to 'hang' vertical for the valve to work properly. i had all this trouble a couple of years ago. i also fitted an electric pump which works on a push switch on the side of my console to prime the engine from the helm rather than wading round to the engine - this has proved to work very well.

jyasaki 27 July 2013 17:08


Originally Posted by Festinghouse (Post 557611)
replace the primer bulb, this has a built in one way valve which often fails allowing fuel to siphon back to the tank.

If the fuel line is sealed up, there should be no way for the fuel to leak back, as the vacuum formed as it receded would keep it there (does that statement actually make sense?).

Someplace has to be letting air into the line to allow the fuel to drain back.


Festinghouse 27 July 2013 17:38

ok, heres an idea, if you have a clear inline filter you will notice that it never stays full, even if you try to fill it prior to connecting the fuel line to the engine. my guess is that the 'air gap' is actually vaporized fuel, and it is the expansion of that which causes the fuel to return to the tank.
i welcome other peoples ideas on this one!

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