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Old 11-27-2011, 04:33 PM
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Gas tank and sending unit question

I took the old tank off my 78 Camaro and the sending unit has one line. The car originally had a 305 and did have A/C. A 350 was put in and the A/C was at some point connected.

The new tank has a vapor line that is cut at the back. The recommended sending unit for a 78 (350) with A/C is a two line unit. That gives me three lines coming off the tank and only two lines from the engine.

So, do I cap the line at the back since the sending unit has a return?
Do I use a single line sending unit and bring a tube from the cut off to the front for the second line from the front of the car?
Do I need to use both the sending unit lines then need a third (and where would it go) line?
Lastly - Is there a manual that would help me find the answer?

Thanks in advance

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Old 11-27-2011, 06:13 PM
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If the pump you run has one line then plug the return on the tank as well as the third(vent)just be sure to run a vented cap.
If your pump has 2 lines I would change it to the single line,
I am not sure when evap systems were implemented in cars, somewhere in the 70s ,The sender with the 3 lines is for a vehicle with a return style fuel pump and an evaporative system.The single is for a straight shot to the pump, no return and no evap.It needs a vented cap, or your system will starve for fuel as vacuum builds in the tank.
I have seen the return style pumps have issues with pressure to the carb in the past, that is why I said to run the single line setup.Less chance of failure
I think the return setup was to help keep cooler fuel to the engine by recirculating it back to the tank, supposedly helping to keep vapor lock to a minimum.Like I said ,IIRC it only causes low pressure issues and delivery volume to the carb as well.

Also it sounds like your car only has one line from the tank to the front, r did I read that wrong?
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Old 11-28-2011, 08:23 PM
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Gas tank and sending unit question

Thanks. I'm assuming that you mean the A/C pump, correct? Also, I was not clear, I do have two lines coming from the front of the vehicle, one (the gas line) along the left side and a second that goes down the right side. Sorry for the confusion.
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