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My filler neck on my rear tank is leaking some, and should be replaced.
Can you do this with the tank in the truck or is it easier to drop the tank? This is the OEM tank between the rear frame rails behind the rear axle.
Also, I'm never sure about using a vented or non vented cap. When I've used a vented cap, when my truck sits in the sun, it makes a giant puddle of gas on the driveway. With a non vented cap I think pressure is building in there to the extent it's pushing out wherever the weakest link is. As of now I'm using a non vented cap after I lost over a gallon of gas last summer in the driveway.
When replacing the rear tank, it's enough of a pain in the neck getting the filler hose lined up and started by yourself I end up with the filler neck loose anyhow - I think you can do it easier with the tank still in the pickup.
As far as vented/non-vented - you pretty much need a vent either way, so if you don't have a vent in the top of the tank, you need one in the cap. I don't know how far back the charcoal canisters went, or when they started venting the tanks, but you should be able to see a vent hose coming out of the top of your tank if you have one - if not, you need the vented cap. Your gas leak could be from having a vent, but the hose is broken/gone, so it's too close - I want to say that the vented tanks without a canister had them run up high under the box side? That way, the gas burped it's way back down into the tank before it could get to the end of the vent hose. I would guess you probably need a vented cap, and if I were a betting man, I'd say your sender gasket/oring is bad, causing the leak.
Evaporative Emission system (Evap/Em): NON vented fuel cap, unleaded fuel. Vapor line(s) route from vapor valve on mid/ship and/or aft axle tank to charcoal canister in the engine compartment.
Ok, I do have the soup can underhood, so it would seem I need an unvented cap. Leaking with the unvented cap is around the hose clamps where the filler tube hits the tank...guessing 40YO rubber is the culprit there. Will order up a new filler neck.
You are pretty much going to have to drop tank to be able to access the metal clamp that holds the other end of the rubber fill hose to the tank. Unless you remove the bed bolts and lift up the end of the bed.
And since the tank is off I'd insp and clean the inside of tank and replace sending unit if needed. Insp sending unit end of the pick up tube sock filter. FYI it is bonded on there with some Ford top secrete stuff.
Great time to go poly tank or up grade to 38 gal....
You do have a fill neck with a vent line? Are you sure your vent line is not stopped up? Do you have mud dobbers in your area??
And FYI the gasket the holds the metal fill tube into the plastic cup that is on the inside of the gas flap, can be a PITA to get off. Gas gets on there and makes it rock hard. You do not want to break the plastic cup on the back side.
Also, I'm never sure about using a vented or non vented cap. When I've used a vented cap, when my truck sits in the sun, it makes a giant puddle of gas on the driveway. With a non vented cap I think pressure is building in there to the extent it's pushing out wherever the weakest link is. As of now I'm using a non vented cap after I lost over a gallon of gas last summer in the driveway.
I'm assuming that, when the fuel makes the puddle, it's coming out of the same place you put it in. Also, I'm wondering how full is the tank when it happens.
Page 81 of the 1976 Ford truck owner's manual says: "Expansion of fuel due to temperature increases may cause fuel overflow at the filler cap when the vehicle is standing or if the cap is removed. To minimize this condition, it is recommended that the amount of fuel put in the tank when filling be limited to the automatic pump shutoff. If your vehicle has two tanks, use fuel from both tanks after fill-up to reduce fuel levels."
I know that some have experienced pump shutoff long before the tank is actually near full, but the principle of not filling the tank up into the filler tube may be a good one.
not coming out the cap. It's pushing out the filler neck where it's clamped to the tank.
Where is the vent line on these?
Not going with the 38 gal rear tank...that's too much weight back there...already have a 100lb bumper with a 100lb spare tire on a swing away back there. I have dual tanks - the other one is in the cab.
Thanks 77&79 for the links...will look at those after I get back from camping this weekend.
The vent line should be right next to (on the front/fwd side of) and attached to the main metal fill neck. Do you have a evap tank with the small rubber line attached to the top center part of the tank that goes to a charcoal canister?
See my 1st attached pic, you can see it right next to the main fill tube.
The vent hose was originally taped to the filler hose (see example in pic below). Ditto when you bought replacement filler hoses at FoMoCo parts counters.
If the vent hose isn't taped, it could collapse.
'Course, these trucks were "slow fill" from day one. People complained, but there wasn't a damn thing we (Ford dealers) could do about it, due to the curvature of the filler necks.
And, with Evap/Em, the situation is even worse, because the gas station nozzles used with unleaded fuel were smaller in diameter than they were with leaded fuel.
Plus, the filler tubes used with Evap/Em had a restrictor in them that would not allow the leaded nozzle to fit in.
On my '79 F150 Lariat Stupor Cab, I could read a chapter of War & Peace while waiting for both tanks to fill...a royal PITA!
The fume recovery pump nozzles used in CA seem to make the filling process more burdensome. While not perfect, pump nozzles elsewhere without the fume recovery feature make it easier.
I rehabbed my rear tank last summer and replaced the filler neck while I was at it. Getting that filler neck on the metal fender-side neck was a chore. The metal neck has a large rib on it, and the hose does not like to stretch at all.
I ended up having to rig up a tourniquet-style clamp to force the hose on. It was one of the jobs where the first 95% was easy, but that last 5% made me want to burn my truck to the ground.
I had to move the hose clamp about 4" down the rubber hose and added another up the metal neck as far as I could. I made a loop under those clamps with some wire and used a screwdriver to twist the wire and take out the slack.
It was still stubborn, and I probably didn't need a clamp in the end.
I had to move the hose clamp about 4" down the rubber hose and added another up the metal neck as far as I could. I made a loop under those clamps with some wire and used a screwdriver to twist the wire and take out the slack.
It was still stubborn, and I probably didn't need a clamp in the end.
That filler pipe can, in most cases, be removed from the fender if it ever proves to be helpful. I wouldn't feel sad about using the clamp. Gasoline seems to have a way of leaking when other fluids wouldn't under similar circumstances.
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