where do these hoses go?

[cruznude]

After stripping all the smog and installing the weber 32/36, I have issues and am tying up loose ends, I still have the charcoal canister and am wondering how or where all the hoses connect up to.  Then under the fuel filter there is another line coming from down below and after looking in a chiltons manual cannot find anything on it. Can some one please help as I think this might be part of my problem.  Thanks to all.  Oh, sorry guys forgot to mention I have a 79 620 KC.

[Stoffregen Motorsports]

Do you have any pics of the hoses in question?

[datzenmike]

Possibly the fuel return line. If this is not connected, then this is once again another problem with ad hoc removal of your emissions equipment. If this is the return line, there is no benefit to disabling it and every reason to expect your truck to be hard to re-start next summer when it gets above 90.

 

A picture(s) would help showing the engine and carb.

[MikeRL411]

Charcoal cannister hoses are color marked with a dot that corresponds to the color dots on the cannister. Fool proof if you haven't tossed the original hoses or were too liberal with cleaning fluid when you degreased the engine compartment components.

[cruznude]

Possibly the fuel return line. If this is not connected, then this is once again another problem with ad hoc removal of your emissions equipment. If this is the return line, there is no benefit to disabling it and every reason to expect your truck to be hard to re-start next summer when it gets above 90.

 

A picture(s) would help showing the engine and carb.

Yea its the fuel return line.  Had to go to U Pull It and saw a 78KC and figured it out at that point.  since I have the weber I assume its okay to plug. Now as it goes for the charcoal canister, ia it necessary to hook up since theres no smog?

[datzenmike]

You missed the point of a return line. All L20Bs run HOT and all have a return line. It's definitely there for a reason. Fresh cool fuel is pumped past the carb and unused is returned to the tank. This keeps cool gas available in hot weather and there is less chance of gas boiling during the summer when the under hood temperatures near the boiling point of water. Engines get hotter for about 10 minutes when shut off and gas will boil in the carb and the lines making re-starts very difficult and often impossible. Another benefit is all the fuel is constantly filtered and this keeps the lines and the tank clean. Next summer when your truck won't start down town, remember this post.

 

The charcoal canister is a storage container for gas fumes from the carb and or the gas tank. When engine vacuum is applied to the purge valve when running, the fumes are sucked into the engine and burned. It's use and operation are totally benign and it reduces gas smells. Serves a purpose but not if removed.

[cruznude]

I understand what your saying DM, its more like a vapor lock w/o having the fuel return le. inUndertand I would like to have it but don't know to apply it with the weber.  Also undertand the charcoal canister but on the canister,(fuel tank) hooks up to the metal line along the firewall on drivers side, (dist) is hooked up to the distributor,and the (purge) where can I hook this up to?  On the opposite side of the feed on the weber is another brass plug and was wondering if I can apply a nipple like the fuel feed side and allowing this to be a fuel return line?  Sorry I can't send pics . Can never figure that photobucket it.

[Z-train]

Carb is irrelevant to return hook up.

[datzenmike]

The stock L20B has a metal line from the pump output to near the carb, turn around, and back to near the pump where it connects to the return line to tank. Near the carb is an outlet on the hard line you can connect to the weber carb. At the return line near the pump is a restriction. Without the restriction the fuel would simply pump back into the tank. The restriction causes the pressure to build (around 3-3.5 PSI) so it will flow into the carb.

 

On the evaporative control (canister) the middle hose goes to the aluminum tank vent hard line on the driver's side. Some others, like California models, also have a hose to the top of the fuel bowl on the carb.

The purge line connects to the base of the small round cap and to any manifold vacuum source.

The vacuum signal line connects to the vacuum advance to the distributor.

 

Engine off... out gassing is collected from fuel tank and stored in the charcoal element.

Engine running... vacuum advance signal opens purge valve allowing air to reverse through the canister and push fumes into the intake manifold to be burnes.

[cruznude]

Thanks DM, all this confusion is coming to an end. You've been a big help.  Just had to take it slow with me and explain.. Thank again.

[JoeCool]

Maybe this will help with what Mike was saying about the fuel return line...

 

This is my setup, right line is fuel line, left side is the fuel return line going back into the tank. It is capped off from the factory by Weber or EMPI because a lot of vehicles don't use a fuel return line. Nissan/Datsun does however. I tried running mine without simply because I didn't buy enough hose, but every time I shut the ignition off the pump would overflow the carb for a millisecond and fuel would splash down onto the intake and exhaust manifold below. So I went to the parts store and bought a 5/16" brass fitting and some more hose and hooked it back up.

 

 

The only line you really need other than that is the vacuum advance hose to the distributor that hooks up to the bottom of the carb. You can remove the evaporative emissions (charcoal) canister but I kept mine and left the fuel vapor hose attached from the tank because I just didn't feel like removing it and I ran two hoses from the EGR portion of the intake to the canister just for looks and the fact that the darn caps kept blowing off! You can see the one directly under the EGR block off plate, the other is above it where the red cap is on the PCV, it has since blown off and now has a hose run to the canister.

[cruznude]

Thanks Joe Cool. Yes, thats what I was thinking about doing there with the return line.  Big help.  Yea I dont have none of the egr stuff on, but will work it out.  Thanks to all.  I'll take it one step at a time.  No hurry.  You and DM all the other ratsuners have good and safe holidays....

[cruznude]

You missed the point of a return line. All L20Bs run HOT and all have a return line. It's definitely there for a reason. Fresh cool fuel is pumped past the carb and unused is returned to the tank. This keeps cool gas available in hot weather and there is less chance of gas boiling during the summer when the under hood temperatures near the boiling point of water. Engines get hotter for about 10 minutes when shut off and gas will boil in the carb and the lines making re-starts very difficult and often impossible. Another benefit is all the fuel is constantly filtered and this keeps the lines and the tank clean. Next summer when your truck won't start down town, remember this post.

 

The charcoal canister is a storage container for gas fumes from the carb and or the gas tank. When engine vacuum is applied to the purge valve when running, the fumes are sucked into the engine and burned. It's use and operation are totally benign and it reduces gas smells. Serves a purpose but not if removed.

Okay all is understood except that if I have nothing to connect up the purgr line up to, can I remove that stock plug on the manifold in front of the first and second cylinder and use that? Just put a brass nipple there.  Just like we have it done for the brake master cylinder?  Or do I have to go some where else?

[datzenmike]

Depends on the intake. All L20B intakes will have a small fitting on the driver's side below the carburetor. The purge line connects into or near the vacuum source for the air inlet snorkel valve for mixing warmed air with cold... but any connection to manifold vacuum will do.

[cruznude]

Thanks DM, I can see this project getting finished soon!