Full Tank Fuel Pressure on a Hot Day... Fuel everywhere.

[Spool]

Is it possible that I don't currently have a Charcoal Canister?

I've never looked for one as I recently learned about this, but I can't seem to locate it in under the hood or along the fuel lines.

-73, C20.

[bd]

The factory location for the canister is to the left (driver side) of the radiator.  Look for a 5/16" steel line in the vicinity that is open and unused.  How many hose nipples are on top of the fuel tank sending unit(s) - 3/8" is supply to the pump, 5/16" is tank vent to the canister.

[Spool]

Wow. I don't have one. Someone removed it.

I'll check back to see where the steel line ends from the tank soon and the sending unit.

The sending unit is on the top of the tank correct? Would I have to drop the tank to check?

[bd]

With some luck, a bright flashlight and flex-mirror combined with a little body contortion will give you an adequate view of the top of the tank.  Wear eye protection and be careful of falling dust and debris.

[Dr_Snooz]

Wow. I don't have one. Someone removed it.

Not surprising. In the years following mandated smog controls, some people had a thing about removing every last bit of "smog crap" as soon as it was legal to do so. It's not something I recommend for reasons you're discovering. Nearly every smog control on a vehicle has a dual purpose. The first is to reduce smog. The second is to extend engine life.

[Spool]

Dr. Snooz,

How would it better my engine life?

I read it holds vapors and uses it for the engine burn later, which would slightly increase my mpg.

But also, without it, years ago, did they just have vented gas caps to relieve pressure?
I've seen that not many people agree a vented gas cap is a proper solution.

[1967KaiserM715]

A vented gas cap can prevent fuel spillage by reducing tank pressure(good) it also lets the harmful gases escape straight into the air-and in an enclosed environment, like a garage, this would be bad.

A charcoal canister will allow the gases to properly vent the tank to reduce pressure, and also acts as a filter to reduce emissions straight into the air.(2 good things)

A charcoal canister is one of the emission things I would keep.


Sent from my iPhone using Tapatalk

[Spool]

I was able to reach my phone near the fuel sensor with ease to snap the photos attached.

There is the one line, as you can see, that I was able to follow down towards the engine, cuts across to the passenger side and then I lost it once it got just in front of the oil pan.
What would the other connector be?

So, if I where to do this the right way, installing a charcoal canister, how would I need to alter the fuel sensor?
My curiosity is why now, after two years, is there pressure building up in my tank? If it's not a charcoal canister that's clogged, than what is it?

In the meantime, I think I may just go with a vented gas cap for now.

[1967KaiserM715]

It's possible you already have a vented cap, and that failed. You have the simple 1 fuel supply sender. I don't know if it's factory correct for your truck, but trucks and cars did come with tanks with just one line, before any real emissions stuff took place.

Sent from my LGL34C using Tapatalk

[bd]

Some 1973 models were constructed without an evaporative emission system (EES).  Either a substitution of parts occurred sometime during its life or your truck was built without EES.  Check for an unused (abandoned) 5/16" steel line running along the frame between the fuel tank and the vicinity to the left of the radiator.  If there is no 5/16" line, your truck was built without EES.  Use a vented fuel tank cap and don't overfill the tank.

[Spool]

Thanks Guys.

BD, When under the truck, I followed the line from the sensor as mention which was isolated before it crossed to the other side.
On the other side it was accompanied with another, but I think it may have been the brake fluid for the rear.

In regards to why it is now, building pressure opposed to before, is there anything that could have clogged something?
Confusing as I would have a full tank in Phoenix with no problem, but now in Los Angeles 2 years later at 75degrees, I can't fill it.

I've attached pictures of my cap. Which I don't believe is vented. I bought this cap from Autozone 2 years ago.

[bd]

That looks like a vented cap and it's probably plugged.  Replace it with a new vented cap.  As a WAG, symptoms could be the result of changes in fuel formulation, either seasonally or geographically, that impact the volatility and/or expansion characteristics of the fuel.

[Dr_Snooz]

Dr. Snooz,

How would it better my engine life?

I read it holds vapors and uses it for the engine burn later, which would slightly increase my mpg.

But also, without it, years ago, did they just have vented gas caps to relieve pressure?
I've seen that not many people agree a vented gas cap is a proper solution.

In your case, it's not doing much to extend engine life. I was referring to your fuel spillage issue. A charcoal can keeps your car from smelling like fresh gas all the time. I had an old Honda that did that. It wasn't a huge problem, but always noticeable. Other smog controls do extend engine life. EGR prevents pinging. PCV reduces sludge. O2 sensors allow for a perfect fuel mixture, reducing thinned oil or lean misfire. Only the cat is purely for smog purposes. The AIR injection is useless, IMO.

[75gmck25]

Your truck has a single gas line on the sending unit, which means it must have a vented cap.  It sounds like your best choice is to just use a good vented gas cap, unless you want to go through the trouble of changing sending units and running new hard line up to the front of the truck.

My '75 with California Emissions has three hard lines connected to the sending unit, using short sections of hose:
1 - gas line to the fuel pump
2 - fuel return line from the fuel pump
3 - vapor recovery line to the charcoal canister under the hood, and then to the carburetor (pulls vapor through the canister)

Using a fuel return line is supposed to have some advantages in fighting vapor lock, since the returning fuel is cooled as it cycles through the tank.  Using a vapor recovery line reduces the gas smell you may get from the vapor coming out of a vented tank.

Bruce