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Old 12-03-2018, 05:23 AM
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4 outlet fuel sending unit

Can the vapor outlet on the sending unit be plugged? I no longer have a charcoal canister or does the vapor outlet also act as a vent.

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Old 12-03-2018, 07:02 AM
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My understanding of the ports on a 4 outlet sending unit are this; however, I'm no authority.
- Fuel feed to engine
- Return line from fuel pump
- Vapor recovery line/vent to canister under the hood
- Vent line running up to the fuel filler neck

I have never seen one with the vent line to the filler neck, but apparently it is needed on some vehicles to let air purge as the tank is filled. I think the vent line running to the filler neck is probably only open when the gas cap is off, so you still need the vapor line for a primary vent.

I would not plug the vapor recovery line unless I also switched to a vented gas cap.

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Old 12-03-2018, 08:11 AM
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You need at least one vent line going to the canister or to below the intake to the proper port. Or a vented cap.

Most systems have 2 at the corners of the tank then a 3rd at the sending unit. Usually the one furthest from the cap goes up to the neck of the cap. In some cases the sending unit port is used for this and the 2 others have roll over valves.

Your best to T the sending unit into another vent port that eventually leads to the intake then block it off completely.
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