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Location:
brisbane
Registered:
October 2004
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elec fuel pump for carbs, return line??
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Mon, 07 February 2005 06:59
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well it seems that all the electric fuel
pump setups for carbs that i have seen
do not have a return line to the tank,
including my own...
why is this?
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I Supported Toymods
Location:
Sydney
Registered:
December 2002
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Re: elec fuel pump for carbs, return line??
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Mon, 07 February 2005 08:35
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Most inline pumps don't need them as when the fuel has no where to go the pump will still only keep the same pressure.
In most cases a mechanical pump by nature will just increase the pressure until something bursts... unless it has a return valve.
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Location:
Kita-Ku, Sapporo, Japan
Registered:
January 2003
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Re: elec fuel pump for carbs, return line??
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Mon, 07 February 2005 10:47
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yup, but be careful as some pumps are regulated to a much higher pressure than you need.. most carbs only need a few psi, like 2-3, and some pumps (i can't remember which i'm thinking of.. holley? carter??) do maybe 7-10psi if unregulated..
there are carb pressure regs too.. ebay for abotu $15 regularly (holley brand)
my "fuel miser 4cyl" pump was internall regulated to 3psi.
Cya, Stewart
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Location:
brisbane
Registered:
October 2004
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Re: elec fuel pump for carbs, return line??
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Mon, 07 February 2005 11:46
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yeah iv got a holley at 3.5psi on 45dcoe webers
what about rising rate regulators, so same pressure
but higher volume(rate) if needed, sounds nifty but
probably unnesssary for carbs dunno? speco make one
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Location:
Tasmania
Registered:
May 2002
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Re: elec fuel pump for carbs, return line??
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Mon, 07 February 2005 12:40
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Mechanical fuel pumps don't need a return line. They hold pressure and will not flow anymore fuel if none is needed. No hose is going to burst or anything like that. Pull one apart and you will find why. The mechanical lever does not pump the fuel, it ust pre-loads the spring. The force of the spring on the diaphram is the only this that pumps the fuel.
I am running a electric fuel pump, to 2 sidedraft Solex carbies. I don't have a return line or a pressure regulator, and it runs fine. I have had a regulator, but it made no difference on any setting, or without. So maybe the pump is running the right pressure and the needle seats and floats are working ok. Or maybe the carbs are flooding and the whole setup is too crude for me to notice? Runs ok, ecconomy not too bad.
New Toyotas do not have a fuel return line anymore. It's to do with emissions. Warm fuel vaporises and creates more emissions, so with no return line the fuel in the tank is left cold.
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