Charcoal canister work around?
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Charcoal canister work around?
I have a 1976 f250 with a 390 engine. The truck has been sitting for 3 years and last week when I took it out the pressure in the gas tanks was building up and causing the truck to choke out. After I released the pressure in the tanks it drove fine again until the pressure built up again. After reading some postings on this site I have narrowed it down to the charcoal canister. The question I cannot get the answer to is: Can I remove the canister until I scour the junkyards to find one? For emissions I would rather keep it or find a workaround. Has anyone found a different canister that works? I read some of the heavy-duty vans have a similar canister is this true? I have also read you can build one... The truck was also running a little hot the last time I took it for a drive (70 degrees out). Is my problem really vapor lock? The gas that did leak out when I released the pressure from the tanks was not really hot at all. . I am replacing the thermostat to see if it was stuck open.
Thanks
-Sp
Thanks
-Sp
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Any similar sized cannister from the junk yard will work from cars or trucks. Some units have a large hose going to the air cleaner and some use a smaller tube running to manifold vacuum that is controlled with a solenoid valve. Is the cannister plugged up somehow? You can disconnect the tank vent line but you may get a strong gas smell around your truck.
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I am pulling what I think is the charcoal container out Friday to see if it is clogged. What I am pulling.. if it is indeed the charcoal filter is under the car below the driver side seat. It has what looks like to be a sensor on it. I have heard it to be a vapor container and charcoal container. There are two lines going into tI am pulling what I think is the charcoal container out Friday to see if it is clogged. What I am pulling.. if it is indeed the charcoal filter is under the car below the driver side seat. It has what looks like to be a sensor on it. I have heard it to be a vapor container and charcoal container. There are two lines going into the unit, one from each tank and one going from what I could follow to the carb. I am simple trying to troubleshoot the over pressurized gas tank(s) and get this beast on the road. This is my first old ford truck project, I am picking up a book this week to do some reading. he unit, one from each tank and one going from what I could follow to the carb. I am simple trying to troubleshoot the over pressurized gas tank(s) and get this beast on the road. This is my first old ford truck project, I am picking up a book this week to do some reading.
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From: SD
They're right. The part you are refering to, under the driver seat along the frame rail, is the tank switch. When you switch from main to auxilary tank, this valve moves and draws fuel from the correct tank. This valve is probably not the problem.
If it was made with a vapor canister (some were not) it would be mounted near the radiator on the passenger frame rail - about the size of a large coffee can. If there is no vapor canister, then you have a different problem. Some fuel caps need to be vented, you may just need a vented fuel cap. Does it do this with both tanks or just one?
Marty
If it was made with a vapor canister (some were not) it would be mounted near the radiator on the passenger frame rail - about the size of a large coffee can. If there is no vapor canister, then you have a different problem. Some fuel caps need to be vented, you may just need a vented fuel cap. Does it do this with both tanks or just one?
Marty
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I would say to have your gas caps checked out.
They should be releasing pressure long before this.
I seriously doubt that it is the charcoal canister. The vapor lines going to it from the tanks however might be plugged. One reason not to top off your gas tanks...
I've seen charcoal canisters filled up with gas cause of this.
Yes I'd definatly have those gas caps checked out or replaced with pressure releasing caps.
They should be releasing pressure long before this.
I seriously doubt that it is the charcoal canister. The vapor lines going to it from the tanks however might be plugged. One reason not to top off your gas tanks...
I've seen charcoal canisters filled up with gas cause of this. Yes I'd definatly have those gas caps checked out or replaced with pressure releasing caps.
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I believe you are right
Thanks for the information....
Yup that was the tank switch all right .. And I believe the gas cap is my issue. I faded out one tank from the switch and let her run for a while. Pressure build up.. Then I did it with the other tank. Same problem. The gas caps that are on the truck are those new locking caps. For emissions testing in Colorado I do not think I can use the vented caps. They check the tail pipe and the gas cap, however my old original 1966 Volvo cap passed so we will see. I will check the other spots for the canister..
Thanks
Yup that was the tank switch all right .. And I believe the gas cap is my issue. I faded out one tank from the switch and let her run for a while. Pressure build up.. Then I did it with the other tank. Same problem. The gas caps that are on the truck are those new locking caps. For emissions testing in Colorado I do not think I can use the vented caps. They check the tail pipe and the gas cap, however my old original 1966 Volvo cap passed so we will see. I will check the other spots for the canister..
Thanks
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Scott,
Please use the FTE default font so All of us can read the text.
All I can read easily is where it starts: "They check ..... "
Users that use small font in their posts usually get over-looked or cause the Reader tro do all thw work by having to make it larger just to read.
To me, this is unfair.
The reader shouldn't have to do all the work to read something
Please use the FTE default font so All of us can read the text.
All I can read easily is where it starts: "They check ..... "
Users that use small font in their posts usually get over-looked or cause the Reader tro do all thw work by having to make it larger just to read.
To me, this is unfair.
The reader shouldn't have to do all the work to read something
Post Fiend
Joined: Jul 2004
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From: Northern California
They do that in california as well. They have to release pressure at a certain PSI or the caps will fail the test. They also have to hold pressure until a certain PSI or they will also fail the test.
The caps when working correctly, should alow fresh air to enter into the tank when gas is burned, but prevent vapors from exiting the tank, unless the pressure gets too great.
It may be that you got the wrong type of locking caps, that are not vented. On certain evap systems a ventable cap is vital, otherwise vapor lock will occur.
The tank instead of being pressurized will be in a vacuum. No air in the tank at all.
Forgive the terminology on the following...
The fuel pump will "suck" out gas until a vacuum develops inside the tank, the vacuum in the tank then "sucks" on the gas at an equal force of the fuel pump and therefore overpowers the pump so no gas or not enough reaches the carb.
I think this is what is happening to you. A ventable gas cap will eliminate this problem.
The caps when working correctly, should alow fresh air to enter into the tank when gas is burned, but prevent vapors from exiting the tank, unless the pressure gets too great.
It may be that you got the wrong type of locking caps, that are not vented. On certain evap systems a ventable cap is vital, otherwise vapor lock will occur.
The tank instead of being pressurized will be in a vacuum. No air in the tank at all.
Forgive the terminology on the following...
The fuel pump will "suck" out gas until a vacuum develops inside the tank, the vacuum in the tank then "sucks" on the gas at an equal force of the fuel pump and therefore overpowers the pump so no gas or not enough reaches the carb.
I think this is what is happening to you. A ventable gas cap will eliminate this problem.
Last edited by 81-F-150-Explorer; May 8, 2006 at 03:02 PM.
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