ATI gasoline aux tank test pressure

One other tidbit to consider. It might not be necessary to close off the rollover vent on the deck tank, and make a closed system. Taking the weight of gasoline to be 6.3 pounds per gallon, you only need about 3 feet of head to equal 1 psi. Now, for the EVAP system the test pressure is 1 psi, so the operating pressure is lower. This explains why in the installation instructions, it is suggested that you may have to close up the system, not you must plug or plumb a return from the rollover valve. You still need a return line from the gas tank to the deck tank. ATI sells a fill line insert, that has two taps, one for fill the other for return. This would make a simple and safe system that does not set a check engine light. You are close on pressures, but I will try the safest/easy way first.

Or to paraphrase this whole thread, it's a major pain in the @ss to direct feed gasoline from an aux tank into the fuel system....

I know a lot of vehicles will turn on the CE light. I pulled into a station decided to gamble with the engine running while fueling. As soon as the cap came lose engine died.
When I got home I tried a few times, no light. Might make trouble if add a tank.
On my old Pete, the pump returned a lot of fuel to tank. When I wanted to get weight down I would shut off the return to 1 tank, and the feed from the other. This way I could stack near all the fuel in 1 tank, turn on that feed, the other off, keep fuel deep in that tank.
Now just trumping. Could you set up a couple of valves so could only use the return to the main tank? 1 switch could start aux pump, kill main pump, open valve from aux, and close a valve added in main supply line. This would keep the system sealed up, except for the line under pressure. (That switch could be a timer)

I have dug into it a little. For gasoline, if you want a deck tank and want to use it as an aux tank, then ATI is maybe the only one. You have to use a pump, return line, and probably close up the system to prevent a check engine light. (Does Titan make one yet? They are pricey.) I plan to wire it in with a timer, and pump gas from 1/2 to 3/4 of the truck tank in my travels.

I have found that people make mistakes, so just like my work days, I run the math again. Even more so when it concerns my own health, safety and property. When you consider that the flash point of gas is about -40 degF and a pick up has plenty of ignition sources, then yea, I am going to look at the system, before installation. The cap on the aux tank still needs its own pressure/vacuum reliefs, I don't want to suck it in or pop it from a line kink.

Three thoughts:

Don't make anything you can't unmake.
What have I forgotten?
How can I make it better?

ATI is the only tank manufacturer that I have been able to find that advertises their tanks for auxiliary use with gas.ATI

To be legal a pump is supposed to be used.

LanceRKeys wrote:
So can these tanks be plumbed directly to the vehicle’s main tank? I have a gravity flow on my diesel, but I will be going to a gas truck next and fear that ford’s 48 gallon tank won’t be quite enough.

Check with the tank manufacturer. Most of the ones I looked at a few years ago where rated to transfer most liquids, or be plumped in for diesel. That might just be CYA, so they don't have to get involved in vapor recovery and all that other stuff.

So can these tanks be plumbed directly to the vehicle’s main tank? I have a gravity flow on my diesel, but I will be going to a gas truck next and fear that ford’s 48 gallon tank won’t be quite enough.

I should hope that the designers of the tanks made them compatible with the vehicle that they are being installed on. It would seem short sighted to market an aux tank that caused the customer's check engine light to constantly be on.

Tip of the lid to ATI. Operating pressure should not exceed 2.5 psig. I will assume the test pressure is 3 psig (just like my diesel tank). The normal max test pressure on a EVAP system is about 1 psig. So, if Ford does not rewrite the book on the 7.3 EVAP system I should be good.

A 2.5 to 3.0x safety margin warms the cockles of my engineer heart. Burst pressure, is probably somewhat higher, however never put it to the test.