Does anyone have info, pics and diagrams of an evap setup using a canister and the plumbing involved including the bracketry and canister location and part nos?
this would be for a 73 f250 2wd
i don’t know if these trucks came evap equipped but I’d like to minimize the fuel smell I get
if anyone has cobbled something together please share

 

When I was deplumbing my 87 F250 460, which had 2 air pumps, 2 canisters, a whole host of pipes and hoses that was totally unnecessary, many of which were burned up in an engine fire, like you I wanted to keep the evap system, or at least part of it. I did a lot of searching through the factory service manual to understand the workings of the stock system, and diagrams from 70's cars which used evap but before emission controls got too complicated. They all more or less work pretty much the same. I was able to pair it down to one of the original canisters and limited hoses. The canister is self venting, and has one hose coming in from the 2 gas tanks, a vapor line from the canister to the carb, and a vacuum hose controlling the purge valve. When the engine is running, vacuum controls the purge valve so you don't have an open vacuum leak while the engine vents the system, and is closed and smell-free when the engine is off.

In my picture below, you can see the hose running down to the lower left that goes to the charcoal canister, the purge valve in that line, and the vacuum hose right next to it that goes to the carb to actuate the valve. All of the parts were from the stock system I was able to salvage after the fire.




Here's a link to another thread I found with a good explanation of the parts involved I thought was helpful.
https://www.fullsizebronco.com/threa...1/post-6161161

 

It’s even simpler than that. A 73 doesn’t have a computer to control a purge valve, so you do not need vacuum or a valve.
You need a canister with one line from the one or two tanks, cap off the midsize one unless you actually have a bowl vent on your carburetor.
The 73 and newer cars and light trucks had the bowl vent, but your, 250 may not. If you’re not sure what that is, post a picture of the top of your carburetor without the air cleaner installed and we can take a look.
Of the two larger ports on the canister, one is covered with what is commonly referred to is a “mushroom cap” because it’s not really a closed off cap. It’s actually there to allow venting, but to keep debris and water splash out.
In fact, lower mounted metal canisters, like would’ve been on a light duty 73, often had a hose from that port, running up to a location on the firewall, so it was higher up and out of harm’s way.
A 2 Wheel Dr. pick up truck probably did not have that hose, and probably had the mushroom cap.
The second large one simply goes to the air filter housing, which is where the vapors get gently sucked into the carburetor.

The other thing you have to worry about is your gas cap. If your truck did not originally come with a charcoal canister system, your gas caps will be fully vented.
Kind of negating the effect of the benefit of the charcoal canister.
That’s a whole ‘nother discussion though, since I’m not sure what it takes to put a one-way vented cap on one of those filler necks.
I think there’s a discussion going on right now about just that subject.

 

There's no computer on my truck to control anything. It's purely mechanical, driven by the ability of the engine to absorb the gasses without creating a vacuum leak. It's a fully sealed system, it's simple and it works. It's just a downsized version of the OEM setup.

 

Gotcha. Thanks for the clarification.
I thought by 87 there would be a computer. And the only vacuum control solenoids I’ve seen were computer controlled, but that was mostly on 86 and newer Mustang and Explorer engines.
I’ll have to check the systems like yours out closer. But as you were saying, as long as there is something to control the valve, so that it’s not pulling vacuum constantly, sounds like you’re good to go.

 

And speaking of 250s with 460s…
Was yours a completely non-electronic carburetor? And was your ignition still fully adjustable?
Even my 83 had an electronically self-adjusting carburetor (non-feedback) with a throttle position sensor, and a lockdown distributor with ECU under the seat in the cab.
that was on an F150, though, so a completely different beast.
Sorry for the slight hijack Jpc, but I was curious how else yours was set up 52merc

 

Yeah, the 87 460 was the last holdout before EEC took over the world. It was the last of the traditionally carbbed engines, used the 4180 Motorcraft/Holley, which is why it had so much fresh air plumbing trying to get it to pass govment regs. I essentially took it back in time to the early 70's so all that's left is the PCV and evap canister, and set it up accordingly. Only thing electronic on it is the original Duraspark II ignition, blue strain box, just like it's earlier brothers from the 70's.

 

Thanks for the replies and info!

the carb was replaced with a Holley 600cfm 2 barrel

there is the strange canister mounted to the firewall. Could it be part of the evap?
there are two lines coming from the gas tank but one has been disconnected. I can’t see the top of the tank where the filler neck goes so not sure.

 

No, that is a simple vacuum reservoir.
Designed to hold additional vacuum for certain things, such as vacuum operated HVAC controls, perhaps some vacuum operated engine accessories, such as emissions components, stuff like that.
So while it might have one or two emissions related functions in its repertoire, it’s not part of the evaporative emissions.
For 73 it would’ve been pretty simple. Probably just the metal charcoal canister mounted down on the frame possibly on the passenger side near the wheel well.
I remember Broncos were on the frame behind the passenger front tire, but even though I have seen them, I can’t remember where the Pre-77 canisters were mounted exactly on pickup trucks.
For 78 and 79 there was a much larger plastic canister mounted on the top of the passenger frame rail, just behind the side of the radiator.
Yours would’ve had just a couple of hoses as I described previously.

Going to study the valve on that 460 a little better to see if I can possibly turn it into something we can use to retrofit our older vehicles.
For most of them though, we don’t use direct vacuum. If that special valve that he was describing is handy and readily available, that might be a game changer for some people.

 

i made a simple PVC canister and filled it with aquarium charcoal. Used scotch brite pads for filters on either end of the canister.

 

That’s awesome!

 

That is awesome, just don’t go anywhere where they might need to look under your truck for security reasons lol.

 

Already some good answers, but I'll add on...generally the same take as 52 Merc. I'll just share what worked for me. The previous owner of my '78 F100 removed the EEC system. I have a vented gas tank that had been plugged, and the old vapor hardlines still existed. The image at the bottom shows my setup. The canister and valve are really low-tech devices. I used a Dorman 994-093 valve and a Dorman 911-198 canister. I park in a garage, and this arrangement significantly cut down on the vapors coming from my fuel tank. Of course, it doesn't address the fuel bowl on the carburetor. If I had a vapor port on my fuel bowl (I don't), I would have tied that into the canister inlet as well. This configuration (+ a new fuel cap) worked for me. I 've been running it this way for about a year.

 

Very awesome thanks so much!
your diagram is exactly what I’m looking for and I bet it will help others,



here is a pic of my carb with bowl vents?
can these vents be incorporated in the evap system!

 

Good question - and poor wording on my part. No, there isn't an easy way to tie into those bowl vents...although it's probably possible with a few well placed hoses and valves. I was referring to an evap port that some carbs have to vent the fuel bowl when the vehicle isn't running. An example is shown below.