So im going through some catastrophic fuel issues at the moment, ive done plenty of research trying to understand the parts tho im admittedly a bit dyslexic so it takes me awhile, im hoping to get a bit of guidance through my specific issue. my goal right now is to have atleast one tank working properly and no gas leaking but im going to try to provide a bit of back story and some pictures here:

So when i recieved the car right tank was over flowing, soon found out they both have pressure issues when the left sprung a leak from the bottom
So at this point left is leaking (alot) right is taking the over flow and not working ( found part of the issue ill post in picture)

As of now i flipped some fuel hoses around and started running off the passenger tank that overflows, but im still getting gas leaking from the driver side (fuel return?) so i decided to take off the service plate behind the wheel because it looks to be where its coming from and theres nothing inside of it except some wires that run to who knows where, i was expecting a leaking fuel sender, but it might be alot worse. also i read there would be the pressure relief valves behind the wheel but the schematic i have says its in the front? A bit confusing here for me as i dont know where to start. took me a half of tank to get to work and back the other day 15 miles and i know 85% sure im not loosing that much gas from the leak, maybe driving with tanks open?

Im going to check the fuel canister since it seems like an easy task hopefully its serviceable to some extent, ill probably just end up breaking it somehow and buying another i have a feeling, and hopefully theres some pressure valves behind it, i dont know why theres so many different sources with different information. but if anyone whos done thing can help me with a checklist or an order of things to check it would be much appreciated. im trying to do this with limited tools since most of mine got stollen with my daily driver im down to 2 jags right now that will be daily driven if they like it or not.




I thought the relief valves would be by that mount but i dont see any fuel line? I didnt try taking off that big bolt. no sender either? maybe what i read was for older models. gas tank almost looks plastic.

yeah so this is why i couldnt pull fuel from right tank, fine with me stay clogged for now

ended up just looping that fuel hose onto itself giving me a 'working' fuel tank that i had to clean, that screw on the bottom is awesome. yes i capped that off also and i bought about 4 fuel filters.

 

The pressure valves are next to the cannister, which is in front of the right front wheel. I'll try to find a pic. You'll probably see one of the valves running in a fore-aft orientation with a rubber connector hose to a metal pipe. The metal pipe clearly runs towards the rear of the car. This is the vent to the tanks. Disconnect the connector hose so that the metal pipe is open to atmosphere. The tanks should now vent and not become pressurized.....assuming the vent pipe is not clogged.

The sending units are reached by removing the tail lights. But the sending units won't have any bearing on your issues; they do not have a history of leaking.

The leaks could very easily be the tanks themselves as they often rust out at the bottom and, from what I see in the pics, I think rust is an issue with your car.

Cheers
DD

 

The pressure valve set-up should look something like this






Cheers
DD

 

Yeah after i drained the overflowing tank i really got no hope for the leaking one ( you can tell by that clogged valve how bad they were, im surprised it ran on that orange gas) i just need to fix that pressure to delay the inevitable. not sure if im committed to replacing them or looking into a fuel cell but id like to keep one of these cars original seeing as i have alot of papers and even a phone i had no clue it came with . the bolts on the bottom fender make me want to consider plan B and C already. Im enjoying the straightforwardness of the design just wish i didnt wait 9 months to ask where that stupid valve was thats actually a massive help, so thanks alot! . I should just be able to poke through the valve with a drill or something instead of leaving it disconnected correct? and my next step i believe it to figure out why the tanks drain into each other. hopefully this is just as straight forward or ill have to redirect more fuel lines

 

Welcome to the Forums. I assume you have a Series 3 (1979 to 1987), the earlier cars had two in-tank fuel pumps. Yours looks like the series3 switchover system with the single fuel pump in the boot.

I had the same problem with the one way plastic valve in the front wheelwell. Yes, take it out and stab a little drill bit through it and that well relieve the tank pressure.

The cover in the back wheelwell is for the return valve wires. I had a huge leak from one of my tanks and after removing the bottom fender panel I discovered it was the short rubber hose from the return valve to the tank. So gas going all over everywhere and it was just a $5 piece of rubber hose and not the tank at all.

Under the rear fenders you'll see a rubber plug or if it is missing you’ll see a big brass plug in the bottom of the tank. Order a bunch of the rubber gaskets for that plug (they cost 84 cents each so order plenty). Then go to the grocery store and get a large disposable aluminum turkey roasting pan. The kind you use at Thanksgiving to bake a turkey. They only cost a couple of dollars. Your going to spill gas so get one of these to catch it. Now you can remove the big brass plug in the bottom of the tank and get the gunk out.

As you probably know, there is the one fuel switchover valve in the boot and in each rear wheelwell there is a return valve. That’s so if your pulling fuel from the right tank the return fuel is going back to the right tank. And vice versa for the left tank. If one of those return valves behind the rear wheels is stuck, broken electrical connection, or just wired wrong by a previous owner (I had that happen once) then gas is going to be returning to a full tank and overflowing.

The first step to diagnosing the leak is to remove the lower fender panel. Get down there and look under the rear bumper side piece and you’ll see some bolts to remove that piece of the bumper. Then remove the big screws on the panel plus a couple bolts in the wheelwell and that panel will come off and then you can see where the leak is coming from. You can still drive the car with that panel off so if you can’t get everything done all at once you can still drive the car.

I’ve been through all the problems you are having so start with these things and let us know how it goes and then if necessary we can give you some further information.

Jeff

 

how many different fuel systems do they have for these cars? When i first opened the trunk i was convinced someone had already been fiddling with it.. but the last owner told me they didnt make very many of this year. doesnt seem like a bad design at all just a bit of a headache if you dont already know where things are. Im going to take care of the pressure and check the fuel canister today and if i have time before it rains ill be on to the changeover valves, not sure if ill be able to source them localy but it doesnt seem hopeful. maybe i can rebuilt them? Ill try to take some pictures for everyone and for future reference if theres not already enough of them, thanks a ton jeff. All you guys helping me out here means the world to me.

 

okay so this is where im at... *sigh* i took out the pressure valves and destroyed the insides, the massive amounts of pressure seem to have disappeared and the left tank that was leaking is intermittent if not at all which tells me its probably that line you were talking about yellow. I did not check the canister seeing as i was excited to try it and really have no clue what to look for... and im still getting less than 5 mpg. which i discovered why, now the fuel is draining into the other tank and its full.. and flooding out of the fuel canister after a fill up (educated guess?) i had to drive it a mile from the gas station and boy i didnt realize how close i was to burning the whole thing down. it started running real rough misfiring by the time i got home the exhaust was glowing down to the back mufflers where my leak is.. guessing the engine was pulling huge amounts of fuel into it via relief passages? after sitting for a few minutes i hear a waterfall under the front, ofcourse its not the cooling system.. yet.. gas is shooting out of the canister!!

So im guessing whats happening here is the return valves are backwards, non functioning ect as you said and what i should do is stop dicking around and just buy the new parts which i did but it will be some time before they arrive.

So in my original post, i should have done the right thing and cleaned out the valve in picture 2 and just put it back together properly since it did work when i bought it and by the looks got gummed up after the drive since it was sitting so long and should work just fine minus draining issues and my fuel leak... ofcourse if i missed something about the fuel canister over flowing please feel free to chime in.


The two valves by the cannister one was not hooker up but there was no flow through it anyways.


after the flooding exhaust was glowing red

gas purging through the cannister



this looks like **** i dont like these high quality pictures, but this is the disconnected tank i didnt use full... gas didnt leak through the top but it came back through the cannister im guessing???


Also found this leak in the engine bay i stopped real quick


Hope someone finds these pictures helpful, im enjoying bonking my head learning. but time for fixed to be fixed!! id take the whole thing apart but im in an apartment and it isnt ideal.. luckily someone moved out and left me a fire extinguisher ive been meaning to get!! If thats not an Omen or a saving grace i dont know what is, id recomend anyone reading this to keep one handy if your doing trial and error with fuel like me. Hope you guys dont mind me documenting my journey to understand these fine and finnicky machines.

 

In your photo of the two valves, the one on the right with a fitting on either end and straight through, that's the one I opened up with a drill bit and it fixed the pressure problem.

I suggest parking your car outside and finding the problem before you drive it. Go slow and safe, we don't want you, your car or anyone else going up in flames.

Every vintage car I have ever owned I always carry a fire extinguisher in the back seat. I made black cloth sleeves for them so they are not very visable and they don't roll around but I can get to it quickly. I figure it's like carrying and umbrella. If you carry it then it won't rain.

 

I agree, thanks for the advice and knowledge. Ive gained back both tanks and they seem to be draining into themselves as they should, ( i think i can hear it with the cap open? ) have to clean out the trunk after messing with the tank switch i spilt alot of gas.. the cabin is really reeking of fuel when the car is stationary and off since i flooded those hoses to the canister. im looking at a diagram here and its showing fuel evaporators. is this something i can service or replace? I want to go over this whole system if possible.. i dont mind an issue here or there but this car in particular does worry me with the fuel smell and how hot everything gets under the hood. i caught the cat glowing just a little bit last night after a freeway drive( its relatively new with a new 02 sensor ) but i wouldn't be surprised if i messed it up already, topic for another thread tho ill digress. ive had quite a few older cars but this one takes the cake.. not sure if the technology used on this vehicle here is the end of something old or the beginning of something new being used.



I also tore up the "3 way purge valve" the other item in the picture hope thats not going to be an issue