the fuel crossover line:

It never will because you only filled one tank. If you have a half full tanks and only fill one tank after it levels off you will be 3/4 full.

Are you having trouble getting the fuel cap off one tank? LOL

 

2) will only take half as much time as 1) above.

 

You need to install, on each end of the fuel crossover line, what is called a "breakaway valve". It is like a check valve that works both ways. It will let the fuel flow through the line to balance the tanks. But if the line is cut or severed by a gator or road debris, the drastic flow will be stopped by that valve. Thus there will be a minimal loss of a fuel spill. If I'm not mistaken it is requirement by U.S. and Canadian D.O.T. to have these on crossover lines. A good way to install is as follows: 1) small ball valve out of each fuel tank. 2) a "T" fitting on each ball valve with a removable plug on the outside. 3) a breakaway valve on the inside of each "T" fitting. 4) and finally the fuel crossover line in the middle. The reason for this is, if the line is blocked or clogging up, you can close the ball valves and unscrew the caps at each end and blow out the line. then re-install the caps and open the ball valves and there you have it a cleaned out fuel crossover line.

The link below is from the FMCSA about all fuel system regulations:

http://www.fmcsa.dot.gov/rules-regulations/administration/fmcsr/fmcsrruletext.aspx?reg=393.65

 

You need to install, on each end of the fuel crossover line, what is called a "breakaway valve". It is like a check valve that works both ways. It will let the fuel flow through the line to balance the tanks. But if the line is cut or severed by a gator or road debris, the drastic flow will be stopped by that valve. Thus there will be a minimal loss of a fuel spill. If I'm not mistaken it is requirement by U.S. and Canadian D.O.T. to have these on crossover lines. A good way to install is as follows: 1) small ball valve out of each fuel tank. 2) a "T" fitting on each ball valve with a removable plug on the outside. 3) a breakaway valve on the inside of each "T" fitting. 4) and finally the fuel crossover line in the middle. The reason for this is, if the line is blocked or clogging up, you can close the ball valves and unscrew the caps at each end and blow out the line. then re-install the caps and open the ball valves and there you have it a cleaned out fuel crossover line.

The link below is from the FMCSA about all fuel system regulations:

http://www.fmcsa.dot.gov/rules-regulations/administration/fmcsr/fmcsrruletext.aspx?reg=393.65

 

You cant "LEGALLY" pull fuel from a crossover line and the one mentioned above pulling from both tanks is a dual feed system "it pulls fuel from the top of both tanks at the same time. Tanks stay fairly even by the simple level effect in that the closer the fuel is to the top of the tank the easier it pulls, so it pulls fuel down till both tanks even out then pulls from both evenly.

The system that started this post is what I have on my classic and it pulls from the top of one tank and has a single crossover line that can be manually shut off to prevent flow to the aux tank. My truck has 2 100gal tanks that give me the option of filling both for 200 gal capacity or shutting the crossover valve and running of off just the main tank (mine is on the drivers side) for 100 gal capacity. ( this system was supposedly removed from production in the 90's for safety reasons. (who hasn't knocked at least one of these lines off and dumped fuel all over the place???)

Again I state you can not have your feed line from the bottom and I wouldn't want to. Pickup line should be from the top and go down till about 1/2" to 1" from bottom of the tank since water and other junk settles and then you can drain this off without it being sucked into the fuel system.

 

Hello Jmlloar.
I never mentioned anything in my post about pulling fuel from the "crossover lines" or as you say having feed lines on the bottom. That is ILLEGAL on ANY motor vehicle except motor cycles. What I mentioned is that you have to have "Breakaway Valves" at each tank so that will prevent fuel loss if the crossover line is ruptured, for it to be legal. My KW has two 150 galon tanks (special order through Kenworth). It is still a dual feed from both tanks... meaning there are two suction lines on the top of the tanks that "T" into one line to the engine. There are two return line that flow through a special "T" fitting return fuel equally to each tank. There are two fuel gauges, a left and a right. There is a "Crossover line" from one tank to the other at the bottom of the tanks to equalize the fuel in the tanks. The crossover line can be blown out by closing the ball valve on each tank and opening the lines clean out ports to remove any moisture or debris from the line. The reason for the two fuel gauges is in case one of the suction lines clog or the crossover gets cloged and the tanks do not balance out, I will know if I am only sucking fuel out from one tank. All this was installed by Kenworth and is perfectly legal in North America.

 

Didn't mean to offend, never meant you said pull from bottom just pointing out not to do it.

Also, you only have to meet regulations that were in effect on the day of manufacture. Otherwise it would be like saying "you cant drive your 1960 B model mack unless it has dual pass air bags installed"

My cabover has nothing other than a crossover hose and one manual valve between the 2 tanks and it is perfectly legal. My 1994 white/gmc came from the factory with dual feed-return lines and a crossover hose with 2 manual valves and it is legal. neither of these have a breakaway valve on them but I can still drive them with no fear of a fine. Most of the laws in the fmcs have the little tag that says "if manufactured on or after such and such date then it must have (this)

 

Furthermore ALL aircooled VW's feed from the bottom of the tanks does that make them illegal to drive??

 

Hey no problem. There was no offence taken. I know things can be taken out of context in forums. The info I posted was from my personal experiance with my W9 and the info from the FMCSA site and the rep I spoke to.

Thanks for the VW info, never new that.

 

You can do a search, dual draw systems have been talked about a lot on this site. It's a very simple system that is usually trouble free if fuel is clean. Trash in tanks is the #1 cause of problems, the best thing you can do is to install screens in the fills. The #2 problem is when someone changes a fuel line it's a little too long and makes an air trap or changes a fitting to a different style/restriction. A 90 on 1 tank and a 45 on the other will cause problems. When changing lines, make them the same length and route them just like factory.

On the suction side, the 2 tanks feed a common Tee, nothing special. The engine pulls fuel from both tanks, simple. On the return side, the engine returns to a tee, but the tee has 2 reed valves in it, 1 going to each tank. In a running engine fuel is flowing toward the engine from both tanks, so the suction line is not a good flow path to equalize the tanks. If 1 tank has more fuel in it than the other, the fuller tank has more fuel weight in it trying to flow (by gravity) toward the lower tank. This makes a slight increase in flow from than tank to the engine, it also resists the reed valve opening on the return side to that tank. So what you get is a more fuel feeding the engine from the fuller tank and more fuel returning to the lower tank. When the lower tank equalizes, so does the flow coming from and returning to the tanks. What really happens is a sort of cycle, 1 tank may have an inch or two more fuel, then it swings to the other side. Back and forth, keeping them close to even, but not perfectly.

When the engine is off, the suction line is becomes the equalizer and gravity slowly equalizes the tanks, as long as there is no air in the system. So if you were low on fuel, not totally empty and only filled 1 tank, it'd take a while for them to equalize (it's only a #8 or 10 line). But if you started the engine, they'd equalize much faster.