Why would gas sometimes come out of the front tank filler hole (where the gas cap screws on) on a dual tank system?

Leothestranded here, yes the same guy that posted the question. After checking with the folks at a local auto parts store, I was informed that Ford pickups with dual tanks are a consistent pain in the pocketbook (and elsewhere) for anyone who drives them! They asked my which tank I was stuck using, as all ford dual tank systems end up having some sort of a problem which results in one tank being unusable (rusted thru tank, fuel relay failing, electrical problems, etc.). I told them I was using the back tank as that was the tank I was using when the fuel tank relay failed (these guys are good). Unknown to me at the time, in fuel injection systems there is a return line from the injection system back to the fuel tank to bleed off any excess fuel the injectors don't need and on a dual tank system that line only goes to the front tank, eventually that tank gets full and overflows. If the relay had failed while using the front tank it never would have been a problem as the fuel would be consumed at a much faster rate than the excess fuel was being returned to the tank. I simply siphoned off five gallons of gas from the front tank & the truck runs fine again as well as not burping gas all over the place. I'll just have to siphon off gas from the front tank every six months or so to keep it from happening again. If you are having this problem and you can only use the back tank, try this first, it might save you some money and aggravation. Good Luck!

Thank you for this! I have a pain in the tush 93 ford f150, whose front tank went kaput, and have been using the back tank. When today in a parking lot noticed the familiar gas splotches on the ground. And thought what in the world now!! I too saw gas filled up in the filler hole, thought maybe I didnt put the gas cap on tight enough and then thought DUH you arent using that tank. Hopped online to see what I could see and low and behold I find your post. THANK YOU so very much for giving some insight into my mind numbing all consuming breaking the pocket book constantly! beast of a ford truck! Looks like Im siphoning gas later!!

I didn't know what was happening with my Ford F 150 1990I have dual tanks the front one was pumping out gas I had no idea what it was doing so I started to check the fuel lines took I put your filter it looks fine

Same thing with my 89 f150. The front tank doesn't work, but it fills up with gas over time. Any quick fix for this problem? I would like to totally disable the front tank and make the excess gas return to the rear. Is this possible?

Seems like a safety recall SHOULD be put in place for safety, environmental and monetary reasons! I did call this same info to Ford about my truck having the same problem. That number is, I believe – 1.800.392.3673 (number supplied by them as I was bounced around) Personally, I'm wondering if the ETHONAL content has become an issue?

from some guy on Craigslis and then when I came home after I got home I noticed gas is leaking and then when I came home after I got home I noticed gas is leaking and I thought it was the fuel lines because I didn't think that it was coming out of gas tank and I thought the wind was blowing the gas again on the fuel line up on the side of the truck making it look like it's coming out of the front tank filler hole and I went we can take and they told me it was going to cost me like $500 to replace the fuel lines cuz really I thought I was going paranoid craz

I simply dropped the front tank and bought brass fittings with caps and put them into the plastic fuel lines after cutting em off and then put hose clamps on them and cut off breather line and put a bolt in it then strapped it all secure to frame. Now running off rear tank. Guess if it works like I understand then I should never fill rear tank all the way as to allow room for any returned fuel?

There is a fuel canister mounted on the frame rail that switches the fuel tanks. It is most likely bad in the way that it is not returning the fuel to the correct tank, causing overfilling of the other tank. My 1989 f250 did the same thing and that was the problem. g

Thanks guys, this puts an end to my mystery with my 1990 300ci f150. When using rear tank, i see level going down rapidly, then when i swich to front tank level is much higher than a moment ago. Funny that the feed so heavily exeeds demand in the first place and really bad that the exess fuel is not returned to tank of origin. But since both tanks are in working order this only brings down practical max fuel capacity to volume of front tank. Many thanks!

$700 i replaced both tanks completly pre asembled got them from amzon also my truck has a return to each tank. I can run on rear tank and never over flow my front tank (93 f150 extend cab short bed)

I am experiencing similar problems with my front tank being the usable one and my back tank overflowing. I crawled under the truck and see that the bottom of the front tank is moist. The back tank completely dry. The cab will sometimes be filled with the smell of gas. I hope it's just fuel line issues.

wicklen, you can totally fill bot tanks, but use the front tank at least 1/2 down before switching to the rear, then back to front when rear is empty, and you still utilize all fuel capacity

It's called the fuel reservoir. It is way top much on amazon and ebay. They also sell a 38 Gallon tank (for the back tank) if you wanna cut it would all together. Auto part stores have metal connection lines so you can eliminate one tank or the other. Personally I wish these rip off artists would sell the fuel reservoir for what it's worth, about 25 to 30 bucks. But they want 80 and up. It switches the tanks according to which tank's fuel pump is running. Probably at least 75 percent of what's going on here. FORD should have a recall, even though it's this old. They had an update years ago, rebate sorta speak, but if you didn't take advantage of it within a prescribed time you didn't get it, it went away. I think it is an environmental hazard, so Ford should fix it.

Sorry about some of the grammar and spelling. I didn't proof read it, it was on my phone, but I think you got the idea.

Ps my truck is a 1987, and yes I think the recall should go that far back.

Ford Motor Company had a recall back then for the check valves to be put in line on both tanks and if you did not put those check valves in eventually the pump for do that

Same issue. Front tank stopped working. (Fuel pump?) Rear works fine. Front syphons off rear if I syphon gas out of front and for awhile overflowed. What's the fix? How can I just disconnect the front tank, syphon out the gas, and keep it from syphoning from the functional rear tank? 93 f150 Greg

I am having the same issue with my 94 Ford f150 flareside. Before my front pump went out completely, I noticed when the front tank ran out of gas and I switched to the rear that all the gas in the rear was being transferred into the front tank and rear would would be emptied. Then I switched back to the front tank and it would have gas in it. Has anyone experienced this same issue? If so, can you tell me how I can stop the gas from being ttransferred? Because the pump in the front is out completely and just need a temporary fix till I can get the cash to get a pump and put it in. And I noticed that after sitting for a while that I'm losing around a 3rd of a gallon of gas and that can add up to a lot of gas after a couple of trips.

I’m having a similar problem with my 88 Ford Econoline 250 XL. The back tank gas gauge seems to be off so we never really know how much gas is in there. The front tank has been purging gas like it’s getting overfilled but we aren’t even putting gas in that tank. When we switch to the front tank, it’ll drive for maybe 5-10 minutes and then act like it’s empty and the van turns off. We’ve primarily been using the back tank since the van actually runs when that tank is being used. There’s also a leak coming from the undercarriage in the right corner area of the drivers seat. How does this get fixed?

is this dangerous?

Yes we still have smokers what if your sitting at a red light and someone desides to throw a cigarette out.

I have aftermarket gas caps that has been allowing the gas to come out when too much gas gets transferred in this 'Cross flow' What happens if you put on tighter caps and then the gas has no where to go??

Same thing, I have only been using the rear tank. I drove it after sitting for 6 months, and when I parked, gas was coming out of the REAR tank I was using(around the cap). It was like it was pressurized, and only a quarter tank full. ??!!