Weird pipe in the trunk

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Burntorange70 said:
Nice explination Dan.
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Thanks.

The best thing to do is unhook and get rid of that whole mess.
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Naw, it ain't! The evaporative emission control system does no harm, and directly saves you money. It traps and condenses gasoline that would otherwise float off into the air, so you get to use the gasoline you bought and paid for. It also reduces gasoline stink when the car is parked in an enclosed space (like your garage). All benefit, zero drawback. It's a stone-simple system; if the lines are messed up just correct their routing and call it good.
 
To late for me it was long gone when I got the car. I would have taken it out any way though. Like a lot of things on my car it weighed to damn much and had to go. LOL I am not woried about fule economy in my 340 Dart. If I want MPG I drive the Neon. But thats just me.
 
Very nice explanation and info slantsixdan!

Feel like I learned something today even though I don't have that unusual vent system in my 74 Calif. car.

Mike
 
Thanks for the very detailed explanation of how it works. I knew what it did, but not how it did it until I read that. Thanks again.
 
So this also explains the "tube" coming out of my fuel pump. WOW. Now I know what to connect to it. Thanks for the info Dan.
 
It's the fill pipe for the moonshine tank.
 
Just going over old topics, my 71' Duster being a canadian car had all the evap system but ws removed long before I got it.

This leaves me with the issue of venting. I ended up drilling a small hole behind the handle on my fuel cap but this isn't the answer.

I had thoughts on finding a filler neck with a vent tube on it and just running it under the car with a duck bill style breather/drain to keep stuff out or are there better ways?
 
Find the vent on top of the tank, and vent to where you want. A sponge in the rubber line will work, just direct it out of water splash.
 
Hi Dan,

So where you mention connecting the purge / fuel tank vapor line into a T to the PCV line, would that cause an issue if the car backfired thru the carb?

Would the flame travel thru the manifold vacuum line to the tank, or does the purge valve prevent this because when the intake manifold goes positive pressure it forces the purge valve to close?
Or does a flame not travel thru a small tube?
Or does the positive pressure from a backfire in the dist advance vac line force the purge valve closed?

Thanks I really have to know in the next .02 seconds.

. :glasses7:





slantsixdan said:
A charcoal can is easy to adapt to non-spec applications. Original types have three ports: TANK (tank vent), CARB or BOWL (carb bowl vent), and PURGE. If you find a replacement with only one vent port ("tank", these are common on fuel injected cars that don't have a bowl vent) you can simply tee the carb bowl vent line into the tank vent line near the canister, then connect this composite vent line to the one and only vent port on the canister. Size does matter here; the late model units tend to be smaller because there's less vapour to handle (no hot carb pouring off vapours).

There needs to be a canister purge valve that only opens when the engine is above idle. Some canisters have these built in (looks like a round "flying saucer" atop the canister itself), but many do not, including Mopars after '72 and most late-model ones in which purging is controlled by the computer via a solenoid. Fortunately, standalone purge valves are readily available and inexpensive. NAPA Echlin # 2-28011:

purge_valve.jpg


Small fitting gets teed into the vacuum advance hose (which should have no vacuum at idle, full vacuum above idle)

Big fittings go inline with "PURGE" hose from canister, which gets teed into the PCV hose.

Whew! It's Miller time. :lol:
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It's a vent pipe in case Valiant Rebel or Dart Doctor are riding in the back seat.... :fart:

It's there to save the front passengers.... :drunken:
 
slantsixdan said:
The system you're asking about is present on '70 California cars and '71 50-state-plus-Canada cars. '71 was the first year all cars in North America (not just California cars) were equipped with evaporative emission control systems (ECS). This first-two-years system is more complex than the relatively simple '72-up system.

The '70-'71 setup uses a complicated fuel tank: there is a small inner tank at the top of the main tank and connected to the main tank chamber by a very small passageway, so that the main tank chamber fills up with the secondary chamber still mostly empty. The gas pump nozzle detects a full tank and clicks off, you hang up the nozzle and drive off. Over the next little while, the secondary tank fills up from the main chamber, dropping the fuel level in the main chamber so as to prevent fuel leaving the tank when things warm up and expand.

These '70-'71 ECS fuel tanks have four vent fittings, one at each corner of the top of the tank. These are brought together in the trunk to a more-or-less vertical vent cylinder leaning against the left wheelhouse — that's what you're seeing. This vent cylinder has five hose fittings: one for the hose from each corner of the tank, and one for a hose connecting to a line that runs up to the right rear corner of the engine bay. it is not supposed to vent into the trunk!

Inside that vent cylinder, each of the four fittings from the corners of the tank continues vertically, each to a different height. The fitting to the engine bay continues inside the cylinder almost to the top. The idea with the 4-corner venting and the different-height pipes inside the cylinder is that no matter what angle the car is at, in what direction, there will always be at least one vent fitting above the liquid-fuel level, so there'll always be a vapour vent, thus preventing pressure buildup that would force fuel vapours out into the atmosphere.

The '70-'71 ECS is also unique and interesting in that it uses the engine crankcase to store fuel vapours piped forward from that vent cylinder in the trunk and from the carb bowl. The interface point is a fitting on the fuel pump body on slant-6 cars, or extra fittings on the engine breather cap on V8s. When the engine is started, the collected vapours are drawn off out of the crankcase via the PCV valve. This system does a reasonably effective job of containing the vapours, since the crankcase is well sealed, but it can cause hot start/hot idle problems, since there is no control over when the vapours are extracted from the crankcase. Most of the unburned hydrocarbons wound up out in the atmosphere anyhow, having been first put through the engine (and emitted as black smoke). :roll:
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So let me get this straight... the 4 vent lines from the top of the tank go into the metal vent tube in the trunk area.. then there's another long line that goes from the vent tube all the way up to the engine compartment, and gets plumbed into the PCV system at the valve cover? So what if I'm running no PCV system?
 
Cal_gecko said:
So let me get this straight... the 4 vent lines from the top of the tank go into the metal vent tube in the trunk area.. then there's another long line that goes from the vent tube all the way up to the engine compartment, and gets plumbed into the PCV system at the valve cover? So what if I'm running no PCV system?
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Why wouldn't you be running a pcv on your car?
The crankcase needs to vent or else it will blow out your gaskets, usually the valve covers.......
 
Cal_gecko said:
So let me get this straight... the 4 vent lines from the top of the tank go into the metal vent tube in the trunk area.. then there's another long line that goes from the vent tube all the way up to the engine compartment, and gets plumbed into the PCV system at the valve cover? So what if I'm running no PCV system?
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The fuel tank vent system and the PCV are separate systems. They just both happen to connect to engine vacuum

Essentially, ORIGINALLY the entire vent system of these tanks ended up being the 1/4" line coming from the tank up to the front. So if you've removed the "carbon can" and rest of the plumbing up front, you need to leave the 1/4" line open to vent the tank at the very least.

(This, partly, is one reason I wanted an older model..........no smog controls)
 
So - I've been digging into some issues my car's having with fuel delivery under heavy load/high rpm when the engine is hot .. it basically drops my fuel pressure down to 0-1 psi ... so I'm evaluating every aspect of the fuel system (1971 Dodge Dart - CA car) ... it had a 318.. I put in an LA360.

So today, I looked at the vent lines .. the 4 vent lines run from the tank to the "pipe" going into the trunk.. they are all new lines.

The 5th line (that runs up to the front of the car) doesn't go anywhere.. when I follow the line up to the front, just below the firewall, the metal line goes to a rubber hose, which is capped off with a bolt. I don't understand what I'm supposed to do with that line.. where's it supposed to go? to the carb? to the valve cover?

should I just leave it?

another issue I've noticed - and not sure if it's related to the venting issue .. I am using a Stant locking gas cap.. and i always have 'leakage' from the cap.. dripping down the side of the car .. very annoying.
 
I guess you have trouble reading?

Cal_gecko said:
drops my fuel pressure down to 0-1 psi ...

The 5th line (that runs up to the front of the car) doesn't go anywhere.. is capped off with a bolt...................... i always have 'leakage' from the cap.. dripping down the side of the car .. very annoying.
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67Dart273 said:
Essentially, ORIGINALLY the entire vent system of these tanks ended up being the 1/4" line coming from the tank up to the front. So if you've removed the "carbon can" and rest of the plumbing up front, you need to leave the 1/4" line open to vent the tank at the very least.
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You have to make sure the 1/4 line is open, high up in in the engine bay, and NOT clogged. Either that or re--do the tank vent system so that it's vented from the top of the filler just like the 69 / earlier cars were. Or........hook up every bit of the carbon can system.

WHAT YEAR is your car? Do you have a shop manual?
 
No - don't have a shop manual ... don't have the stock breather system either ...

and just to rib you back ... perhaps you have trouble reading too ...
so I'm evaluating every aspect of the fuel system (1971 Dodge Dart - CA car) ... it had a 318.. I put in an LA360.
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;)
 
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