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Drop Tank questions

Started by _youngy_11_ , Jan 22 2010 11:18 AM

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8 replies to this topic

#1 _youngy_11_

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Posted 22 January 2010 - 11:18 AM

Hi, I have a drop tank in my LX feeding a efi V6.

I filled it up all the way for the first time yesterday and noticed a small fuel leak when I got home.

It was coming from the plate ontop of the tank where the internal efi pump is. The plate has a gasket and from memory had a good seal.

I have noticed that when taking the fuel cap off a sucking noise, i.e the fuel tank is under negative pressure.

Is this acceptable?

All I have coming from the tank is the feeding fuel line and the return fuel line. I don't need a breather or anything do I?

Im thinking that the negative pressure has pulled the seal in, and I have only noticed it now due to the full tank and a bit of hard cornering.

I just found a photo.
Posted Image

The breather outlet on the other side was blocked off as I was too close to the exhaust.
Thanks Ryan

Edited by youngy_11, 22 January 2010 - 11:26 AM.

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#2 76lxhatch

That was easy!

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Posted 22 January 2010 - 03:55 PM

You should have a breather somewhere - with the engine using fuel the return line is never going to return as much as the pump pulls out

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#3 ls2lxhatch

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Posted 22 January 2010 - 03:57 PM

You will need some sort of breather system to allow air to replace the fuel as the tank is emptied. A breather system is also required to allow for fuel expansion on a hot day.

The factory petrol cap has a two way valve that allows air in or out if the pressure exceeds a preset amount. There are also breathers connected to the charcoal cannister.