Gas tank vent

WZ JUNK · June 01, 2016, 08:13:10 PM

I used a gas tank and throttle body engine from the same donor car in my 1954 Chevy project. I eliminated the charcoal canister used on the donor car. My concern is that the canister was also the vent for the fuel tank. I do not think the gas cap act as a vent on these vehicles but I am not sure. Without a vent I am concerned that the tank will pull a vacuum as the fuel is depleted.

If I need a vent, how can I provide one? I am considering the use of a pcv valve attached to the line that formally went to the charcoal canister. I would add the pcv to the charcoal canister connection on the tank with the pcv placed so that gravity would hold it closed as it does when the engine is at rest. The pcv will act as a check valve. It would need some kind of air filter to keep dirty air out of the tank. This valve would allow air to enter the tank as the fuel is depleted but would self close when the engine is not running. Maybe there is a better way. Do you have any ideas?

John

enjenjo · June 01, 2016, 08:36:40 PM

John. I have just run a vent line with a G2 fuel filter stuck in the end, there has never been any problems with this setup.

WZ JUNK · June 01, 2016, 09:02:39 PM

Quote from: "enjenjo"John. I have just run a vent line with a G2 fuel filter stuck in the end, there has never been any problems with this setup.

That would work. Can I use the tank connection that went to the charcoal canister?

John

kb426 · June 01, 2016, 10:23:21 PM

I'm using that line from my tank on the 51. I'm just letting it out in the free air. Sometimes you can smell fumes. The original line was plumbed into the air inlet that was removed.

enjenjo · June 01, 2016, 10:54:51 PM

Quote from: "WZ JUNK"
Quote from: "enjenjo"John. I have just run a vent line with a G2 fuel filter stuck in the end, there has never been any problems with this setup.

That would work. Can I use the tank connection that went to the charcoal canister?

John

That should work.

Beck · June 07, 2016, 10:48:41 AM

I'm sure you know this John but, for others watching.

If the vent line is routed correctly, normally across the top of the tank to the far side, then down to the bottom of the tank the line works as a roll over protection. No matter which way the vehicle would wind up after a roll over the fuel cannot run out the vent.

GPster · June 07, 2016, 01:02:33 PM

Going back to the beginning of this subject, doesn't the elimination of the charcoal canister give you a "Check Engine" fault? I thought that there was one of the sensors on the throttle body that is on the line to the canister. I thought it was all tied into the same fault you would get if you gas cap wast loose or not on (or the tank over filled?). I know there are a lot of hints on how to rejuvinate the charcoal canisters and they aren't cheap if you think they need replaced so I wonder about just eliminating them. GPster

WZ JUNK · June 07, 2016, 03:08:55 PM

Quote from: "GPster"Going back to the beginning of this subject, doesn't the elimination of the charcoal canister give you a "Check Engine" fault? I thought that there was one of the sensors on the throttle body that is on the line to the canister. I thought it was all tied into the same fault you would get if you gas cap wast loose or not on (or the tank over filled?). I know there are a lot of hints on how to rejuvinate the charcoal canisters and they aren't cheap if you think they need replaced so I wonder about just eliminating them. GPster

I do not remember any sensors on my system for the canister. I had all of the plumbing in place and the canister mounted and then I was told by a dependable source that I did not need it. I removed it from the car at this point. It is possible that I am using an earlier throttle body system that predates the sensors you speak of. (1989)

John

jaybee · June 10, 2016, 11:56:22 PM

Late models use a purge valve operated by the PCM, whereas older models didn't...what with not having a pcm.

papastoyss · June 11, 2016, 11:53:26 AM

Quote from: "GPster"Going back to the beginning of this subject, doesn't the elimination of the charcoal canister give you a "Check Engine" fault? I thought that there was one of the sensors on the throttle body that is on the line to the canister. I thought it was all tied into the same fault you would get if you gas cap wast loose or not on (or the tank over filled?). I know there are a lot of hints on how to rejuvinate the charcoal canisters and they aren't cheap if you think they need replaced so I wonder about just eliminating them. GPster

I think this would be a factor only after the advent of ODB 2 which came in during 1995 & was mandated across all lines by 1996 model year.You wouldn't believe the # of cars that came in our shop w/check engine lights on because the driver didn't tighten the gas cap or gassed up w/the engine running because they had always done this w/their ODB1 ride.

GPster · June 11, 2016, 04:14:39 PM

That 1995 model year explains my question . I'm dealing with a '87 GMC S15 which was the reason for the question. I remember our '99 Jeep Grand Cherokee giving us a problem with check engine light on a trip to New Jersey. Getting gassed up to come home the technician that pumped gas didn't tighten the cap and we got to worry about the light the whole way home and we hadn't had the vehicle very long. My '03 Ford Ranger wile give me that light after I fill it up at some gas pumps. It seems to fill so fast that full doesn't leave any vapor space in the tank and I'll get the warning..Good to have all the explanations. GPster