Evap Emission System

[Mach1 Driver]

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.

 

[Mach1 Driver]

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??

 

[73pony]

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.

 

[midlife]

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.

 

[Mach1 Driver]

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?

 

[Mach1 Driver]

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.

 

[Mach1 Driver]

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.

 

[Don C]

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.

 

[secluff]

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.

 

[jpaz]

I thought a garage with and old car was supposed to smell like gas!

 

[Pastel Blue]

I thought a garage with and old car was supposed to smell like gas!

Not really... and not good for your long term health.

 

[Hemikiller]

Any car with an open element air cleaner is going to stink of fuel until the carb dries up. I have an original style air cleaner on my 71 and have never smelled fuel in the garage. Then again, my garage is not hermetically sealed like a newer house.

 

[Mach1 Driver]

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.

I was looking for a 71-73 manual to see the illustrations you provided from the 65-72 Ford Master Parts Catalog. Thank you so much, that is extremely helpful.

As for leaks etc., I'm the original owner and it has had leaks in the past, particularly from the economizer valve on the bottom of the carb, and once from the acceleration pump. But currently it is in good repair with no leaks. It just smells like all pre-1970 cars do. They were designed to vent to the atmosphere from the tanks and carb, so they are doing what they were designed to do. All our previous houses had detached garages, and I thought the smell when we opened the door was from the lawn mower. Imagine my surprise when we finally bought a house with an attached garage and have a lawn service. That puppy will stink-up the garage for at least a week after it has been run.

The tank, and fill pipe are normally the same on 69s and 70s, so I'm not sure where the vent connection is made. My car has an indent in the fill tube in the sealing surface for the gas cap to vent the tank. Pretty crude huh? The evap system was first installed on 1970 Mustangs in California only, so there must be other parts involved. 

I'm glad you found the illustration for a 1970, as they are most like my 69. What I find interesting is the vapor separator valve that appears to be mounted to the drivers side subframe. I found one at West Coast Classic Cougar for a mere $179.10 used. I'm not sure how this works exactly. It has a line running in and out and appears to have a foam media where perhaps it also pulls-in air? I'm not sure what the point of that would be. It would be good to know if there is a hole in the subframe for the passage of air. A picture is attached. So a line somehow connects to the tank or fill pipe, then goes to the vapor separator valve, then to a tee. One side goes to the crankcase vent and the other to the canister. Then from the canister to the air cleaner via a corrugated hose.

There doesn't appear to be any connection to the carb bowl vents (where I get most of my smell). This is perplexing.

 

[Fabrice]

Mine was stinky during and after it ran. Even my cloths would smell "mustang" and staying in garage while it ran was kinda suicidal...

Ditched the good old 650 DP Holley by an EFI and bad smell/fumes are gone. It runs much better and cleaner too. I no longer get these "1 more minute in garage and you dead" fumes.

Next is to connect the valve cover breather, that is also emitting much less vapours now, to the old vent line and put a small bike filter near tank (the vent on tank is now return line point).

Before and after the EFI, I ran same 2 high flow K&N air filters, clean and oiled (one on carb, one in hood) , no intake/engine changes.

There are much more pluses for EFI's vs carbs, but just this makes the swap worth it.

 

[Mach1 Driver]

Mine was stinky during and after it ran. Even my cloths would smell "mustang" and staying in garage while it ran was kinda suicidal...

Ditched the good old 650 DP Holley by an EFI and bad smell/fumes are gone. It runs much better and cleaner too. I no longer get these "1 more minute in garage and you dead" fumes.

Next is to connect the valve cover breather, that is also emitting much less vapours now, to the old vent line and put a small bike filter near tank (the vent on tank is now return line point).

Before and after the EFI, I ran same 2 high flow K&N air filters, clean and oiled (one on carb, one in hood) , no intake/engine changes.

There are much more pluses for EFI's vs carbs, but just this makes the swap worth it.

That's exactly what I would expect- going with an EFI eliminates the two vented fuel bowls on a DP Holley. Whose EFI are you using? If the vent line is now the return line, then the canister must not be connected to anything at the moment?

 

[Fabrice]

I run a Holley Snipper, but a FITech or any EFI would do the same if properly installed.

[if the vent line is now the return line, then the canister must not be connected to anything at the moment?]

The gas tank on 7123 has a vent gap on top. The old metal line that was used originally for fumes to go back there

is currently unused. The original fuel line has been replaced and another return line added. This new return line

goes back to tank via what was the original vent gap hole. While unconnected atm, I kept the old vent line because I want the breather fumes to be redirected

to a filter thru it. Even in its twenties when the old canister was in place, the car had unpleasant vapours entering the cabin from time to time

because the ventilation is right above it. So I want to recycle that line to have engine crank fumes moved to where the ventilation cannot pick it.

As said above, since the swap, its like a modern car, all the nasty smelly dangerous gases are gone. Or better said, they are so reduced, they feel like gone.

in this thread, you can see picts of at least 3 installs and details about the tank changes.

https://www.7173mustangs.com/thread-holley-sniper-efi-and-robbmc-surge-tank-351c-and-fmx?highlight=Sniper

 

[Mach1 Driver]

I run a Holley Snipper, but a FITech or any EFI would do the same if properly installed.

[if the vent line is now the return line, then the canister must not be connected to anything at the moment?]

The gas tank on 7123 has a vent gap on top. The old metal line that was used originally for fumes to go back there

is currently unused. The original fuel line has been replaced and another return line added. This new return line

goes back to tank via what was the original vent gap hole. While unconnected atm, I kept the old vent line because I want the breather fumes to be redirected

to a filter thru it. Even in its twenties when the old canister was in place, the car had unpleasant vapours entering the cabin from time to time

because the ventilation is right above it. So I want to recycle that line to have engine crank fumes moved to where the ventilation cannot pick it.

As said above, since the swap, its like a modern car, all the nasty smelly dangerous gases are gone. Or better said, they are so reduced, they feel like gone.

in this thread, you can see picts of at least 3 installs and details about the tank changes.

https://www.7173mustangs.com/thread-holley-sniper-efi-and-robbmc-surge-tank-351c-and-fmx?highlight=Sniper

Thanks, that's good info. I took a poll on a couple of other forums and though just posted, so far the EFI respondents agree that the gas fumes are gone. All of the cars are older and don't have canisters, so that confirms my suspicion that the fuel tank doesn't add much if any noticeable odor and the carburetor is the culprit.

 

[Mach1 Driver]

Now, back to one of my earlier questions; Filling the Tank. My 69 has always vomited fuel out the back on nearly every filling. Unless you fill it with an eyedropper it spits back at you. Your 71-73s have an air space in the tank top and an internal tube in the tank running over to the fill tube, and the fill tube has a baffle running up inside that mates with the tank tube. This is part of the vapor recovery system, but I'm wondering if it helps when filling the tank- do yours spit gas back at you when filling???

 

[Hemikiller]

Now, back to one of my earlier questions; Filling the Tank. My 69 has always vomited fuel out the back on nearly every filling. Unless you fill it with an eyedropper it spits back at you. Your 71-73s have an air space in the tank top and an internal tube in the tank running over to the fill tube, and the fill tube has a baffle running up inside that mates with the tank tube. This is part of the vapor recovery system, but I'm wondering if it helps when filling the tank- do yours spit gas back at you when filling???

Never had issues with the tank spitting back when filling on any of my 71-3s. 

This guy has a 70 evap system for sale if you wanted to go that route.

http://mustangmania.com/parts/844/

A simple test to see if you can contain the fumes would be a fully functioning closed element air cleaner with a 71-2 style charcoal canister hooked up.