I have finally pulled the trigger and have started buying parts for my 1979 f150 so i can work on it in the spring. I ordered the 38 gallon without eec for my truck and upon looking closer it says until 1978 not 1979 for fitment. I looked on the forum but could not find the answer of is it a matter of it not fitting or is it an epa thing. As far as i knew the frame should be the same and as long as I run a vented cap i think I'll be ok. Any ideas would be apprectied.
thanks

 

I would like to know that myself.....

 

I cant think of any issues, I have the 38 gal tank on my 78 F250 SCAB.

 

EEC is the abbreviation for Electronic Engine Control (aka onboard computer), no 1970's Truck/Bronco/Econoline has it.

What you are actually referring to is the Evaporative Emission System, abbreviated Evap/Em.

Evap/Em uses a NON vented fuel cap and unleaded fuel. The fuel tank* has a hole in it adjacent to the fuel sending unit for the fuel vapor valve.

A vapor line routes from the valve along the passenger side frame rail to the valve on the charcoal canister located on the frame rail, usually below the alternator in the engine compartment.

Evap/Em was introduced in 1970, was initially installed on all Passenger Cars, F100's, Bronco's and Econolines that were sold new in CA

By 1979, most states mandated Evap/Em.

*If the F100/350/Econoline has Evap/Em and two fuel tanks, both tanks will have a vapor valve.

If NY doesn't have a smog test and your truck has Evap/Em, using a non Evap/Em tank won't be a problem.

Here in CA it's a different story, as CA smog tests all 1976 and newer vehicles.

 

Ok, figured it was just an emission thing. The non emission tank isn't listed for 1979 so I just wanted to make sure it would fit. It doesn't have the vent in the tank now in the 19g tank just a vented cap so I figured it would work just wanted to make sure

 

Just a heads up on your tank swap:


I have a 78 F150 and put the 38 gallon tank with EES in it but sealed the hole and didn't use the evap plug/line to a canister since I didn't have it already. My stock 19 gallon tank didn't have EES either. Due to my 38 gallon tank not having a way to vent it builds pressure and after a day or so will pressurize the tank to the point it starts to leak fuel out of the sending unit hole. It would release the pressure when the fuel cap (vented but only to allow air to be vented in and not out) was taken off and the leak would stop. I stuffed a rag in the fuel neck to keep gas from sloshing out until I can either find a cap that vents out, or drill my current cap to allow it to vent pressure.


Also, If you haven't already go ahead and extend your sending unit float arm so your fuel gauge will read more correctly than running it as it is now.

 

I cut the evap line approx 5 inches long and put a check valve on it to release pressure. My cap is also vented

 

Thanks for the Info, my tank now builds pressure and when I take the cap off it goes whoosh. So I drilled a very small hole on top of the metal part of filler neck and havnt had an issue since.

 

thanks for the info

 

I went through 3 McParts store caps before I drilled my own with a very small bit.

 

Had to drill tiny hole in my replacement cap too. It was suppose to be correct. Same thing with all Chinese translations, lacking a bit.

 

i heard its due to caps being able to vent in not out, not sure if its true or not but thats what i was told by someother guys on here.

 

That's what mine was doing.

 

One other thing that Ford changed for the different tanks was the location of the fill-vent tube (the big one that burps the system while filling up with gas) from one side of the large fill tube to the other.
So if yours has the fill-vent to the front of the filler hose and the one you get has the fill-vent to the rear, it "officially" does not fit.
That's not to say that you could not make it work, but for most it's probably a bit awkward to do.

And I don't know if that also changes anything in the shape of the tank that might make it hard to fit with the existing hardware, but anything's possible.
But all the tank manufacturers I've read details on have that little tidbit about the fill-vent location in their descriptions of why the one for most trucks is $200 bucks and the one for mine is $500!!!!!
I never bought the expensive one, and was not ready to spend 200 on an experiment either.
Hopefully it all works out for you.

And correct on the venting of the cap. Basically all caps are "vented" one way or the other, but later caps were only vented one way (inward) to allow for air to take up the space when the fuel is used. But not allow pressure (from heat expansion or whatever) to push fuel vapors outside into the atmosphere. Instead those later ones vented their pressure into the vapor recovery (EVAP) system and it's charcoal canister.
Like the lowly PCV valve then, it's basically a good type of smog control.

Paul