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1973 240z fuel lines


J.T.

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Due to fuel contamination/fuel starvation I dropped my tank and am having it reconditioned. I'm also replacing the electric pump and all the fuel/vent lines. I have searched the threads and read about fuel lines, evap tank and electric fuel pump. But am now confused -Today I crawled under my Z and removed the old lines and found that a previous owner had removed the electric pump and cut what looks to be the fuel return line. The fuel supply line on my car is a rubber hose running along the passenger side and up through the front passenger wheel well to the carb.

Not original right? Fuel lines are actually pipes running down the trans tunnel right? Keeping the car original is not my concern -being able to drive it is. Everytime I think I get this car drivable I find another previous owner mod (Doh) that keeps it in the garage.

To further complicate things I took my Z to a non Z specialist at the beginning of my problems and they put a huge Holley 4 barrel on (which let me drive it for a bit before I had contamination/starvation issues).

What am I looking for to hook up to the fuel return line? Does the fuel line running along the underneath of the passenger side sound safe? Should it be pipe? If I complete the fuel circuit will my problems go away?

Thanks

JT

PS. Anyone working on previous owner short cuts -I feel your pain.

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The fuel return line is there to route excess fuel back to the tank, as well as to help prevent vapor lock and like conditions. By getting the tank reconditioned, and completing the fuel line circuits, some of your problems should go away. You should be able to get away with rubber all the way from back to front, but I would probably replace them with hard lines or SS lines at some point for safety. They came that way for a reason.

Some of the later 73 240Z came with both a mechanical and an electrical fuel pump. On earlier versions with the flat top carbs, the electric fuel pump was added to help prevent vapor lock, which these cars suffered from due primarily to the flat top carbs. You should be ok without the elec. fuel pump since you no longer have the flat tops, however I'd rather have a quality elec. pump over a mechanical. I have both in mine and it looks like the elec pump was added at some point along the way, prior to the flat tops being replaced by round top SUs.

As for the Holley carb, assuming they didn't go over 390 CFM, you should be ok, although I think that number is really more appropriate for an L28 that's been pumped up a bit. I believe the stock SU carbs were capable of moving around 250-275 CFM...Anyone?

Note that this is all based on the knowledge posted on this board and others and not based on personal experience.

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As enigma said . Hard lines are the safest. The metal lines ran in the tranny tunnel on the passenger side to keep them away from the exhaust heat . They extend forward from the tank to the front of the engine bay . At the radiator support the metal line stopped and rubber was used to connect to the filter. Again rubber to the mechanical fuel pump . Then rubber to the fuel rail which runs around the front of the valve cover and down the side of it . Each carb then has a rubber line connecting to the rail for supply . The fuel rail makes a 180 turn and now is a return line . It runs next to the supply back around the front of the engine and rubber line then connects it to the metal return back to the tank . The end of the fuel rail is closed off , but has a vary small hole that restricts the flow back to the tank and this keeps the pressure up in the system. The return line allows the excess unused gasoline to flow back to the tank and this also keeps the cool fuel from the tank supplying the carbs . Where your supply line is at the tank , right above it is the return line stub out. There is a vent line above this near the top of the tank . this runs to the evap tank . the evap tank then has a line that runs up front and ends on the driver side up under where he ignition coil is mounted . There it is connected to a diverter valve that has three outlets. One to the engine breather from the block . One to the stock air cleaner , this supplies clean air to the fuel tank . If pictures would help let me know . send me a PM Gary

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After reading Enigma's post I checked to see what size Holley I had and it is a 600cfm w/electric choke. Is this too much? I looked around for a fuel return and saw the metal fuel line cut on the side wall of the engine bay. What would not having a return fuel line do to my car? Make it prone to flooding?

Are the metal fuel lines available to purchase anywhere? Is dropping the driveshaft necessary (I'm sure it makes it easier) ?

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  • 3 months later...

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