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Old 09-23-2005, 17:35   #1 (permalink)
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fuel emptying from whole system

My 351 XY has a 600 Holley, stock mech. pump. If I don't start it every 5 - 7 days fuel evaporates from the bowls and drains back as far as the fuel pump.
It may be going back past the pump as well as it takes an awful lot of cranking and sometimes won't get fuel up by itself.

Mate suggested that fuel may be siphoning out of system into fuel tank.
There are no leaks anywhere and no evidence of fuel dripping out of boosters or throttle shafts while sitting. Even the filter is empty.
The car has a vented cap and vented standard tank.

If I start it every 5-7 days it starts first crank usually.

Has anyone had any similar dramas?

Thanks Northey
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Old 09-24-2005, 02:03   #2 (permalink)
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Re: fuel emptying from whole system

The 1 way valve in the fuel pump is either stuffed or what your actually seeing is the bowls aren't empty it's just the accel pump on the carb doesn't work. Does it flat spot when you boot it?
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Old 09-24-2005, 02:13   #3 (permalink)
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Re: fuel emptying from whole system

I used to have the same problems years ago when i ran a 302c and 600vac. If i didn't start it for a week, it was real real hard to get going. I have never had this prob with the BG carby, but did allways have an electric pump too. Maybe brenx is onto something.
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Old 09-24-2005, 02:40   #4 (permalink)
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Re: fuel emptying from whole system

A number of times now I've removed both sight screws after the car has sat for a week and both bowls are empty. The acc. pumps don't even have fuel in them.
To save all the cranking I use a squirter to fill the front bowl until the pump will squirt and then the car starts easily.

The acc. pump works ok. As soon as the throttle is touched fuel squirts.

I've looked few times at around five days and there is some fuel in bowls but no sign of fuel weeping on gaskets, etc. Everything around inside and outside of carby is dry.

I understand that it can drain back to the pump because of a faulty valve but that volume of fuel (2 bowls, lines and filter) then has to go somewhere else. BTW the fuel pump doesn't leak either. Not externally anyway.

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Old 09-24-2005, 02:43   #5 (permalink)
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Re: fuel emptying from whole system

If the valve is faulty it won't leak externally. Another thing to check is the power valves not leaking. I honestly can see how it'd empty all of that without any sign. Is it boiling the fuel?
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Old 09-24-2005, 02:51   #6 (permalink)
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Re: fuel emptying from whole system

Powervalve is new, gasket not torn or damaged.
It's not boiling fuel. The car is not being driven at moment and it only gets run until engine is starting to warm up. That is when temp gauge starts to move. I can still rest my hand on block after running.
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Old 09-24-2005, 02:55   #7 (permalink)
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Re: fuel emptying from whole system

Next time you turn it off get a torch and look down the carb. You'll probably see fuel dripping. Somethings a miss with that carb.
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Old 09-24-2005, 15:10   #8 (permalink)
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Re: fuel emptying from whole system

Couldn't reply earlier - computer not running well. Mate, been there done that. No fuel dripping from boosters.

That's why I got interested in the siphoning theory. Even if the carb were leaking, that doesn't explain the filter being emptied. If, as Brenx suggested earlier, the 1 way valve in pump failed, that means the fuel has to return to the tank. Is that possible?

Know it seems unimportant but its a right royal pain in the dot having to remove shaker, air cleaner, etc and fill a fuel bowl so I can start car every week.

Any suggestions welcome.
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Old 09-24-2005, 15:45   #9 (permalink)
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Re: fuel emptying from whole system

Quote:
Originally Posted by northey
That's why I got interested in the siphoning theory. Even if the carb were leaking, that doesn't explain the filter being emptied. If, as Brenx suggested earlier, the 1 way valve in pump failed, that means the fuel has to return to the tank. Is that possible?
It's more than possible. It's a reality. I've seen it happen with my own eyes. The car I saw doing it had a fuel filter between the pump and carb. Not exactly the best place to put the filter but it'll do. Due to the filter being their I could watch the fuel drain back. It'd just bubble away and drain.
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Old 09-24-2005, 15:58   #10 (permalink)
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Re: fuel emptying from whole system

Good one Brenx, I'll look some more.
Thanks for replies.
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