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Click on above. This is the way it was done in the early '70's. The vac connection on an LS engine is a 1/8" barb hose connection, way in the back near the power brake booster connection. Or you could just use a vented gas cap.

 

the gas fumes from a open vented vehicle in a well sealed up garage are annoying, use the charcoal canister to vent the tank, you will need a valve on the purge hose

 

I agree with this. I run an open vent from the tank and the fumes are very noticeable. At times they might be considered offensive and will force me into looking for a gas leak in the engine bay.

I'm not knowledgeable about using a charcoal cannister, but perhaps I should be using one. I'll do some reading on it. If you guys have any good info on it, then I'm all ears (or eyes lol.)

 

My charcoal canister vent hose used to go to a port on the lower front of my old Quadrajet, but I had nowhere to connect it when I swapped in a newer carburetor. My canister and vent system (original from '75) did not appear to have any type of check or purge valve, so it seems the old carburetor drew vacuum through the canister all the time.

I first tried using a T into the PVC line and connecting the canister vent there, since it seemed to be almost the same place as the dedicated vent port on the old Quadrajet. However, this seems to make the carburetor run too lean in cruise mode (I have a wide band AFR gauge).

In my latest change I put a 1/4" nipple on the body of my stock air cleaner and I have the hose from the vapor canister connected to that nipple. It will draw canister air in continuously through the filter, but won't affect the mixture for the carburetor. I'm going to see how that works.

I also considered using a stock TBI spacer and its 3/8" hose fitting to connect the canister vent line. However, the orientation of the tabs on the base of the spacer is different than the orientation of my stock air cleaner, so i can't mount the air cleaner properly.

Bruce

 

This has a billet cap installed in the back of the cab




Here is my 72 eec fuel tank layout. I copied the 72 eec vent system but made a small change to the vent line layout so in the event of a roll the fuel will stay in the tank. Could be on my roof and not loose a drop.




I have had a number of old rides where if you get off camber enough your basically dumping fuel out onto the trail. That and the fact I want to run door less without having my head rignt next to the fuel fill made a sealed system a good choice.



Here is the current evap hose routing. The air pump is non functioning so that hose off of the J port has been eliminated going to the air pump and I just have a hose going to the egr solenoid otherwise it is as shown.




The thing has a 3/8 brake vent tube going to the tank and the purge valve opens sending the fumes into the throttle body

Stole this from another site on the TBI evap solenoid operation.

The ECM completes the solenoid ground path, energizing the solenoid to block purge vacuum and de-energizing the solenoid to allow the canister to be purged. The ECM energizes the solenoid during cold engine operation, at idle and when the vehicle is stopped with the engine running. The ECM de-energizes the solenoid and allows canister purge during normal engine operation, with the throttle open and road speed above approximately 5 m.p.h..




Now the fun part.
A LS engine uses a computer controlled a 2 part valve evap system. One solenoid/canister at the rear to Vent then a line running to a second valve at the engine to purge the vapor.



Here is a simple short video on replacing the purge valve on the intake.

The thing just pushes in there with a o ring seal held in place by a bolt.


I am thinking of just making a steel plate to "block off" the solenoid then re use my TBI canister and TBI purge valve and just have a rubber hose going that block off plate tapped and threaded with a hose barb on the 5.3 to purge it into the intake. Not sure if I will have a isue with that o ring seal doing this though.

I could just drill out the internals of the 5.3 purge valve so I know without a doubt the thing seals or go the other way and drill/break/tap out the purge valve on my 3 port(tank, vent, purge) TBI canister running a line to the 5.3 purge valve


Then have the thing purge some how????

Maybe using a relay off the brake light switch so anytime I break at a light or when I hit the brakes on decel the thing purges?

Emissions is being eliminated when I do the pcm. The thing is already a factory egr delete because I live in a non emissions state. But I don't want the computer involved in anything it does not need to be doing.

But I still need the thing to purge that tank so I don't rupture my tank which would be real bad with the tank inside the cab.
Double edged sword running it in the cab. The chance of rust/tank damage is greatly diminished(I live in Michigan where stuff rust fast) No need for a massive tank skid plate or the thing sitting low to hit on things and the need for forward and reverse baffling is eliminated. The thing also gravity feeds through 3 different spots to the pump so there is no change of the pump sucking air.
But being in the cab that tank needs to be fully without a doubt sealed or I am going to know it right away.

I am thinking the brake light/relay thing will work just not 100% on that so open to what you guys have done here and ideas.

 

I would just connect the 5.3 purge solenoid to your charcoal canister. The 5.3 computer will already be programmed to run that solenoid. If your old purge solenoid on your canister is normally open then you can just hook up to it's hose and draw through it.

You don't need the second solenoid at the tank, though you might have to install a ressistor into the harness so that the computer thinks it's there and doesn't set a code. Or leave the 2nd solenoid connected to the harness, just not connected to anything.

On 70's carbureted engines, the charcoal canister purge had a vacuum operated valve to open the purge to manifold vacuum. They had a coolant temp valve to block the system when the engine was cold. And used a type of vacuum port that supplied vacuum to the purge valve at part throttle only like the ported vacuum advance did. EFI throttle bodies don't have that type of vacuum port, so your best, simplest solution is to use the 5.3 purge solenoid. Even when the purge solenoid is closed, the fuel tank still vents through the canister so you won't hurt your tank.

Many late model computers monitor that the evap system is holding vacuum, and if not sets a code. So hopefully, your system is not programmed to do that, or you will have to find a work around for that as well.

Sent from my moto x4 using Tapatalk

 

I am basically doing the the exact same thing with my 02 as this guy did with his 01.

https://youtu.be/1lpuIiPB2sk?t=201

2 power wires(not including starter/grounds) simple hookup to run it in stock form.

I am not sure if the guy removing the vats on my computer can retain the purge function or not. I mean it would be nice if it was still active. But I don't know if it will still be active so I am approaching this like it will not be active and those that have done these swaps are using a vented cap.

Contacting him Monday to find out on that and set up a time to flash the ecm sitting right next to me.

Going through this thing on the stand and throw new gaskets in it then basically call it done to get ready for mounting it to the manual and getting the swap stuff around. Run the thing for 30-50k and then replace the short block with another in the 150 range to run that for 50 more thousand.

Going to be able to have a light for codes and I will be able to use a reader. But using basic gauges so I won't be looking at anything flashing or some log data screen if I do get a code.

 

The solenoid back at the tank performs one function.Diagnostics.

It is called the canister vent valve or canister closed valve.It basically closes and allows vacuum to build during a diagnostic check by the computer.
The purge valve opens briefly as the canister valve is closed.Then the purge closes trapping vacuum in the hose.There is a pressure sensor in the tank.(very important to have if you want to run without a check engine light)
When it sees that vacuum is held at a specific amount ( via tank sensor) for a given amount of time ,it passes the monitor and runs the next one.
It is open to flow the rest of the time, to vent fumes through the canister, where they are absorbed, -- and to let fresh air in so fumes can be pulled through the purge solenoid on the engine when the purge solenoid is active,
allowing the fumes to be burnt in the engine

The tank pressure sensor should be easy to install on any retrofit.It would be ideal to put it up high with an extension hose to keep raw fuel from entering.

Or simply delete that function from the tune

 

http://67-72chevytrucks.com/vboard/showthread.php?t=733068

The above link shows pictures of the eec system in a stock application. I will show them tonight.

I basically copied it and just cross crossed my lines on top of the tank so if the thing was on its passenger side fuel could not flow down to the canister.

My 87 canister has a tank, vent, and a purge valve.

The tank runs to the tank.

The vent is open with i am guessing a one way check valve so when the tank empties the vacume pulls that check valve allowing fresh air to flow into the tank line and the tank.

The purge runs to the port on the throttlebody to be pulled into the intake.

Now i could just run a low3-5 psi check valvle removing the purge valve which would allow that pressure to escape to the outside air like a vented cap does.