1976 F250 Camper Special gas caps leaking

[islandboy315]

I have a 1976 F250 Ranger XLT Camper Special with a 460 and dual tanks and am having problems with fuel leaking out of both tanks at the gas filler cap. The gasket seals seem to be ok, but after driving it for about 10 minutes or more, pressure builds and gas slowly oozes out and has damaged the paint a bit. Tried replacing gas caps but it keeps doing it. Engine is also running very rich and a little rough. I had a problem a while ago with a hole in the gas line and the truck wouldn't start, they fixed that but it does still run rough.

Thoughts?

Thanks in advance.

 

[m78]

Look at the hoses where they clamp to the filler and vent. Sometimes they dry out and split.

 

[islandboy315]

The gas comes out the fill cap, not before it. The gas caps are flush with the truck body and are not behind a door.

 

[m78]

woops, didn't pay attention to the year. Maybe its because your truck is upside down.
Maybe Dennis knows where the vents for the tanks are on that truck. (Could be plugged.)
I also remember another thread where vented or unvented gas caps were discussed but wouldn't know where to find it.
I have unvented on my truck.

 

[islandboy315]

Thanks, will look for that thread. Funny about the upside down truck.

 

[Beach66Bum]

and he doesn't even live in Australia

 

[Mil1ion]

Usually hot climate causes expansion.
Is your problem..fuel sloshing around ?
Try stopping after first click off..... when refueling.

Hope this helps

 

[miottimouse]

check that the vent on top of the tank is not plugged

 

[Ozzie]

I also have a 1976 F-250 with a 460. It is a Ranger, but not XLT and not Camper Special. Mine also has the dual tanks. Some trucks had the evaporative emission set up and some didn't. Mine came from San Jose, and therefore has the fume pot and related plumbing. As you know each tank has its own style cap to match the fender. Each comes in vented and non-vented types and locking and non-locking types. I haven't had any overflowing problems with mine. As has been suggested, either don't fill it to the brim or run each tank down a little, check for venting, and make sure you have the proper caps. The standard caps vent in & out. The evaporative emission caps have one way valves. They allow air to go in but prevent fumes and fuel from coming out. The systems are described on page 24-50-1 through page 24-50-37 of the shop manual, volume 2.

 

[BKW]

Evaporative Emission = NON vented fuel cap.

 

[Big Jim F150]

I have a 78 F-150 Ranger Lariat, which is a Trailer Special, with the 351M / 400 engine and I also have the dual tanks and mine will flow gas from the fillers but mine are behind doors on the side of the bed, mine will do it if it's hot outside and I know that gas will expand when it's hot outside, especially if the truck is parked so it's not sitting level with the drivers side facing downhill, and sometimes both tanks do it, but I've tried filling to the first click, and I've also run the offending tank down a little, for that I switch from one tank to the other, and try to park where it's level, but sometimes it will still do it. By the way I'm running a four barrel Holley carburetor, and my truck originally come out Texas, but it was built in Dearborn Michigan, so it's not a Cali rig. I don't have any emissions stuff on it. Any ideas to what I can do or have done to solve the issue before it screws up my paint job, for this truck is mainly used for shows and cruisin' but it also gets driven in "motorcycle" type of weather.
Thanks for the help, and information.FTF really Rocks!!

 

[BKW]

I have a 78 F-150 Ranger Lariat, which is a Trailer Special, with the 351M / 400 engine and I also have the dual tanks and mine will flow gas from the fillers but mine are behind doors on the side of the bed, mine will do it if it's hot outside and I know that gas will expand when it's hot outside, especially if the truck is parked so it's not sitting level with the drivers side facing downhill, and sometimes both tanks do it, but I've tried filling to the first click, and I've also run the offending tank down a little, for that I switch from one tank to the other, and try to park where it's level, but sometimes it will still do it. By the way I'm running a four barrel Holley carburetor, and my truck originally come out Texas, but it was built in Dearborn Michigan, so it's not a Cali rig (does not have to be).

I don't have any emissions stuff on it (Uh huh).

Any ideas to what I can do or have done to solve the issue before it screws up my paint job, for this truck is mainly used for shows and cruisin' but it also gets driven in "motorcycle" type of weather.

With CA emissions doesn't make any difference. What does make a difference is if the particular state required emission related parts or not.

For sure, it has PCV .. and could also have had an EGR valve, T/E (Thermactor Emission-smog pump), Evaporative Emission, and a cat converter.

And since the 4V manifold has been added (no 351M/400 installed in a passenger car/F100/350/Bronco/Econoline came w/a 4V originally), it's possible all the emission parts have been removed by a previous owner...probably because TX may not require a smog test. I'm CA born and raised, have lived here for most of my 70 years .. so I'm unaware of what other states emissions requirements are.

Here in LA LA Land, a member of t'other site has a 1976 F350 390 4V Stupor-Duper Camper Special that was sold new in NorCal. He bragged in his signature that it had no smog equipment on it. I knew that wheeze was false and I also knew he had no clue what to look for.

So, one day I drove out to San Berdoo and looked at it. Raising the hood, I see a chrome air cleaner, Evap/Em charcoal canister with all the lines missing, plugs in the heads where the T/E manifolds were once connected, PCV removed, EGR plate blocked off...etc. And since the guy didn't notice this when he bought it, he's up **** creek without a paddle!

Because...CA smog tests all 1976 and newer vehicles which means it cannot be registered until all the original smog parts are replaced. He's in the same boat today, as I looked at it in 2008 and he's done nothing since then to fix it.

The only fix that I know of is to run one gallon of gas less when you fill it up. I bought a 1979 F150 400/C6 Stupor Cab new, it leaked gas from day one...until I figured out what the problem was.

Don't fill the tanks to the brim!

 

[Big Jim F150]

Thanks Bill, I'll do that. But what was the cause of the fuel leaking problem on your 79 F-150 Super Cab with the 400 C6 combo ? And what did you do to resolve the problem? I forgot to mention in my last post that I have an Edelbtock intake manifold. And I still have a PCV valve on it. Should I have vented fuel caps, or do I need the non vented ones with mine being a 78?
Thanks in advance.

 

[BKW]

Thanks Bill, I'll do that. But what was the cause of the fuel leaking problem on your 79 F-150 Super Cab with the 400 C6 combo ? And what did you do to resolve the problem? I forgot to mention in my last post that I have an Edelbtock intake manifold. And I still have a PCV valve on it. Should I have vented fuel caps, or do I need the non vented ones with mine being a 78?

When you fill the mid-ship and/or aft axle fuel tanks all the way up, gas will seep out (due to expansion) during hot weather or if the truck is parked on the slant.

So the trick is, once you know the capacity of the tanks, when filling, omit at least one gallon.

And btw: These tanks have been "slow fill" since new and there's nothing that can be done about it, as it has to do with the curvature of the fuel filler tubes.

No Evaporative Emission = Vented fuel cap(s) / With Evaporative Emission = NON vented fuel cap(s)

With/without Evap/Em: Not only are the caps different, but so are the filler tubes. Evap/Em also requires unleaded gas.

 

[jloggi12]

I have a 1976 F250 Camper Special that my daughter drives and she is having the same issue here in AZ. when her truck sits the fuel comes back out the fuel caps and its happening with both tanks. We have parked on a slant and flat and it happens when the truck is on both spots, is the key just to keep the tanks less than full?