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Evap Emission System
#1
nuke 
Hi guys, I'm a newbie here, and for good reason- I own a 69 Mach. One of its problems is that my wife doesn't like to drive in it because it stinks up the garage. Ford started with the evap system in 1970 in California, and then refined it in all the 71-73 cars. For the older cars, the garage smells like gasoline until the fuel in the carb bowl dries-up- about a week later. For some reason the venting tank doesn't seem to smell as bad.
I have a general idea how it works, but not the particulars. I would like a good shop manual that has an illustration of the system, showing it in entirety. Can anyone recommend one?

I know that the changes are as follows:
1. The tank has special venting going into the fill tube, and a 10% bulge on top that provides an air gap. The tank actually mounts below the trunk floor, instead of becoming the floor of the trunk.
2. The filler neck has an internal vent and mounts differently than the older cars.
3. The vapor separator helps keep raw gas out of the line to the canister.
4. The fuel cap lets air in at .25 psi, and out at .75 to 1.25 psi. This is normally sealed with the engine off. My 69 has an indent tooled into the top of the filler pipe sealing surface to act as a vent. This brings up a question- are your cars hard to fill? Mine vomits gas out the back nearly every time I fill it up. I'm wondering if the changes to the system make it easier to fill?
5. And of course the addition of the carbon canister.

So you can see that I know the basic components, but I can only guess at how the are connected. Usually these systems go from tank to vapor separator, canister, purge valve to carb. Sometimes the purge valve is mounted on the canister and sometimes it is separate. The purge valve is triggered by teeing into the distributor's vacuum advance. This helps prevent hard starts, since the ported vacuum to the distributor doesn't kick in at start-up.
Any help would be appreciated to get ol'smelly out of the garage.
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#2
I just realized I made an assumption here that I shouldn't have. I assumed that the 71-73 Mustangs do not leave a smell of gasoline in the garage after driving- is that correct??
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#3
That is correct. Welcome to the forum.

I do not have the schematics. But here is how mine is set up. Keep in mind this is not stock complete.

There is a return vapor line running from top of fuel tank inside the trans tunnel. It connects to the charcoal canister. The charcoal canister then connects to a fitting on the air cleaner.
'73 Grandé H Code. Headman long tube headers, T-5 Transmission, 3.70 Traclok, Lowered 1" all around, Aussie 2v heads w/ 2.19 intake, 1.71 exhaust, screw in studs, full roller cam 608/612 lift 280/281 duration LSA 112, 750 CFM double pumper, Holley Street Dominator intake.

'73 F code convertible. Bright red. Needs total restore. (IE HOT MESS)

- Jason
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#4
All old cars can leave a smell of gas. The carb can leak, as can fuel lines. Combustion with these older cars is less complete than newer cars. Exhaust systems can leak as well.

Hell, even I inadvertently leak at times, and the wife complains that I smell as well. It's a sign of old age.
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#5
(12-06-2017, 04:15 PM)73pony Wrote: Keep in mind this is not stock complete. There is a return vapor line running from top of fuel tank inside the trans tunnel. It connects to the charcoal canister. The charcoal canister then connects to a fitting on the air cleaner.

These aren't quite the earliest systems; those would be in the 70 California cars, but I expected more stuff. With just one hose into the canister and one out to the air cleaner, then I can see how it could cause hot start and idle problems when the vapor is pulled into the engine at startup. This was apparently a problem in the 71 Chrysler system, so in 72 they fed it off the ported vacuum for the distributor, because ported vacuum doesn't exist at idle. I would expect a line running from the carb bowl vent to the canister also. That's what gives mine the most smell.

Hopefully someone can recommend a manual that has an illustration of the system. Anyone know of one?
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#6
(12-06-2017, 06:05 PM)midlife Wrote: All old cars can leave a smell of gas.  The carb can leak, as can fuel lines.  Combustion with these older cars is less complete than newer cars.  Exhaust systems can leak as well.  

Hell, even I inadvertently leak at times, and the wife complains that I smell as well.  It's a sign of old age.

Of course, but if you don't have those problems and it still smells of gas... I just blame the dog. Hey Mid, I love your avatar on this site. Big Grin
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#7
[Image: carbon_canister.png]
Good Golly Miss Molly, that is the monster of all carbon canisters. So it does have just two tubes- one big and one small, with what looks like a "in vent" in the middle. If there is a purge valve it must be separate. I'm anxious to see how this works.
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#8
They have no purge valve. The canister does not vent directly to the carburetor, but to the outside of the air cleaner housing, outside of the filter, so it works with very low vacuum and the fumes are well mixed with fresh air before getting to the carburetor. The fuel vapors are drawn out of the canister over a period of time, while driving.

I would check your filler cap gasket, and check the carburetor for external and internal leaks. These are the most likely areas for the fuel smell to come from. The vent holes in the carburetor usually aren't much of a problem, the air cleaner usually keeps them contained. The accelerator pump and power valves are common places that leak, as well as the bowl gaskets on Holley carburetors.


“If you can't explain it simply, you don't understand it well enough.”
--Albert Einstein
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#9
Mach1 Driver, Hello and welcome to the best Mustang forum you could have found. (We like all year Mustangs) I don't have any 69-70 Shop Manuals. The illustration is from the 65-72 Ford Master Parts Catalog. The 70 system functions the same as the 71/ system with everything being in about the same location with the exception of the  fuel vapor separator valve not being tank mounted. The valve (9A153) is at location "F". The system functions by storing vapors from the sealed fuel tank through the vapor separator valve to the carbon canister where they are stored. Upon engine crank up they are pulled into the intake system via a corrugated  tube from the canister to the air cleaner housing. The same carbon canister is used for 70-72 applications. The large cap is basically an auxiliary or back up vent "Just in Case".  I'm running the original 4300  series carburetor on my 71 3514bl with the evaporate system intact and have never had any fuel smells.
Like Don C posted I would take a good look at the integrity of the fuel system to make sure all seals are in good shape and you have no carburetor leakage.


Attached Files
.jpg   70 9a153_LI.jpg (Size: 1,010.51 KB / Downloads: 67)
.jpg   70 evap 1_LI.jpg (Size: 1,020.04 KB / Downloads: 79)
Steve

No Officer...I really don't know how fast I was going, my speedometer stopped at 140!
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#10
I thought a garage with and old car was supposed to smell like gas!
run_horse Run Horse Run!
John 72 Q Code
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