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Nuts & Bolts: Need to Vent a 1978 Jeep CJ-7

Posted in How To: Engine on December 30, 2016
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Need to Vent

I have a 1978 CJ-7, which I am rebuilding. I am running new fuel lines to a new tank and a new fuel sending unit. I cannot find replacement parts for the check valves and charcoal canister. I have read forums of others having the same problem. There seems to be several ways to solve this issue, and I am leaning towards capping off the venting loop to the charcoal canister and using a vented gas cap. I would appreciate your input.

-Bruce J.

A charcoal canister’s purpose in life is to trap fuel vapor from the tank (and often the carburetor) rather than allowing the vapor to vent to the atmosphere. The vapor is then periodically routed to the engine intake for eventual combustion. How that happens varies a lot depending on the vehicle, but charcoal canisters have been around since the late 1960s and are one of the few emissions components that really do more good than harm. Therefore, it’s worth keeping if you can.

You are correct: Charcoal canisters and the valves on the tank have long been discontinued for your CJ-7, so new direct replacement stuff isn’t an option unless you somehow stumble across some NOS parts. We understand wanting new components since you are doing a full rebuild, but neither the charcoal canister nor the fuel tank check valve are known for going bad. Therefore, you might just consider using what you have.

If your stuff is damaged or missing, used components pop up all the time on eBay and occasionally on Jeep forums. If you are leery of that, the last option would be to use components from a newer vehicle, such as a YJ or early Cherokee. You’ll need a charcoal canister with the proper ports and some kind of check valve in order for the system to work properly. It will take some research, but if you study the system on your Jeep, you should be able to find a suitable donor. It’s worth keeping a charcoal canister if you can, as they really do cut down on the fuel smell and also help the environment.

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