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Old 31 October 2011, 13:27   #1
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Ribcraft 4.8 fuel problem

Hi all,

I have a problm with my RC4.8 in the fact that i could small petrol when i walked past the boat today and thought i would have a look. I opened the fuel filler and out gushed a good load of fuel (it had obviously been resting against the cap). I filled it after last use last week but not like that its impossible to do that! Have taken the breather off and blown down it and heard the fuel bubble up then shoot up out the breather hole (if that makes sense). Is this right?? Seems like air is getting in to me but has anyone any ideas on this one. Sorry the newbie quesion!!

Many thanks

Si
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Old 31 October 2011, 13:54   #2
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It's quite warm here at the mo. Same with you? If you filled to the brim with cold fuel, I wonder could it have expanded a bit? Or are you parked on a bit of a slope?
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Old 31 October 2011, 19:23   #3
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I thought this but to be honest the amount of fuel that came out was probably a litre or so would take it down below 'brimming'. I park the boat where i fill it so it doesnt move at all. Just cant work it out at all....
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Old 01 November 2011, 01:07   #4
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I'm with Wilk...as the fuel warms it expands and parts of it will vaporise developing pressure. The smell was the vapour under pressure being forced out the breather (which will be relatively small in size). The gush when you released the cap was the liquid fuel under pressure being ejected.

Cars manage this phenomenon these days with relatively complex vapour management systems. Boats don't have that...

If you fill up with fuel at the garage, don't trickle it in beyond the pump automatic shut off. If you fill up from cans, make sure you leave an expansion volume above the liquid level...I'd suggest at least a litre.

Also, but much less likely...is the breather breathing or could it be blocked in some way? I know you've said you can blow through it but (presumably) that's with the filler cap open...is there any inrush of air into the tank when you remove the filler cap after a period of running? Any fuel starvation problems with the engine as a result of a vacuum developing within the tank that restricts fuel flow?
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Old 01 November 2011, 07:48   #5
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I suspect that the filler and/or breather pipe aren't at the highest part of the tank.

Ie if they are at the "downhill" end of the tank as the boat is parked there could be air/vapour trapped in the "uphill" end of the tank that had expanded forcing fuel up the filler / vent.
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Old 01 November 2011, 11:42   #6
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Thanks for the replies. I have had no issues with a fuel vacuum when in use and yes the breather was tested with the fuel cap open. I am guessing then from what you have said that its a build up of pressure in the tank. I will keep an eye on it and then let you know.

Many thanks for your help.

Si
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