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Discussion Starter #1 (Edited)
The truck is almost completely done! Woohoo. Just need to take care of some particulars.

Need some help with the fuel tank:

Right now it consists of a tank with two AN-6 fittings (one for fuel and one for fuel return), and a non-vented cap. I worry that when consuming fuel that the tank will build a mild vacuum inside the tank and starve the injector pump on the Tdi.

What do you guys think? Does it need a breather? If so, how would you do it. Vent the tank with an open hose routed up high with a rollover valve? Vent the tank with the same thing plus a check valve (assuming it would open to air when under vacuum)?
Could I just run a t-fitting in the return line very close to the tank and route it up high (or put a check valve in) and hope when the vacuum gets high enough it will suck air?

Orrrr, will it just work with the tiny leaks that are prolly present in the whole system.

Thanks for the help,

Billster
 

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Shouldn't be any problem Bill. You have a closed loop system, deeeesil to boot. You'll pump what you need, and return the rest.

There might be a problem with excessive presure build up (with gas but with d?), but not with vacume.

Run it. See what happens. 99.9% possitive you'll have no problems.

--D
 

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I am almost with RR on this one. The only thing that would concern me would be heat related expansion. I "think" that the diesel evaporation rate is MUCH lower than gasoline, but I don't know how much, and it gets damn sunny/hot down there.

I am of the run it though too, but maybe, just maybe with a vented/pop off cap. I don't think it's a big deal either.

j
 

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I think you need a breather, not so much for expansion, but also to prevent your tank from imploding as you suck it dry. Stop and think, you have a sealed system - what happens to the pressure inside the tank as you suck 5,8 10 or whatever gallons of fuel out? The tank comes under vacuum and may collapse like a 2liter bottle of coke.

Disregard this rant if you are running a fuel cell, but even then, there may be some other issues.
 

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I'm with Busto on this one. Venting will relieve any problems of expansion/contraction and consumption.

Definitely include the roll-over valve. FWIW, there any of a number of "Conservation" vents used in industry to alleviate just this issue with much more interesting liquids than diesel fuel.

Peace,
Paul
 
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