Fuel spilling out if tank and about 9 miles to the gallon

[vannahrose15]

Hey guys I don't know if you can help me out. I bought this car about 3 weeks ago and the fuel system seems to be a big problem. Every time I go to gas it up if I don't take 20 minutes to slowly fill it up gas spills out of the tank from where I am filling it. I fixed the pressure problem it had by getting a new ventilated cap from the auto store but it still spills and when I tracked my mpg's I'm getting barely 10 to the gallon on a car recommended at 22. Also I can smell unburnt fuel whenever I'm driving so I feel like I have a leak somewhere but I just don't know where or what to do. I appreciate the help
I have a 1977 Datsun 280z
 
 
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[Zed Head]

Sounds like something is blocking your filler hose.  The hose is big, you should be able to see all the way down and in to the tank, from the top, in bright sun or with a flashlight (edit - actually this might be harder to do on a 77 than a 76).  You should also be able to poke a long skinny rod or stick down in to the tank also.  Could be that a PO has done something weird to your filler hose, maybe got a kink in it.  When filing the fuel should drop directly n to the tank, no obstructions at all, if the filler hose is properly attached.

You can also take off the inner panel and see the hose from the inside of the car.  That's where some people get gas fumes from, leaks in the filler hose, inside the cabin.

Edited May 6, 2017 by Zed Head

[Mark Maras]

  Ditto on the blockage. Remove the inner panel carefully, especially if it's cold. They can crack when flexing them. (voice of experience) Heating the panel first with a hair dryer is a good idea. I would put the car on stands or a lift rack and inspect the fuel system front to rear for leaks BEFORE I dealt with the blockage. The blockage is a PITA but fuel leakage is hazardous to your health AND your Z's.

[zKars]

Fuel filling problems are often caused by a problem with the vent air return hose that T's into the filler hose near the top. Air has to escape out the vent line as the tank is filled BEFORE the nozzle of the filler, or the air will try to escape back out the main fill hose triggering the release on the gas station knozzle. 

Chances are you have broken cracked vent lines. 

[gwri8]

Head's up.  If you are going remove the passenger side rear panel, be careful as it can snap if you don't take a couple things off before hand.  The rear deck is raised and you will have to also remove the small deck panel on that side first. I highly recommend removing the window strut metal flange also. The one on the body over the panel.  It makes it easier to take the panel out without too much flex.

[Zed Head]

Venting problems do sound likely if you have the unleaded "shutter".  But even most shutters have vent holes built in to them.  Somebody with a 77 or 78 filler style would know better.  On my 76 you can look directly down and see your reflection in a pool of gasoline in the tank.

[vannahrose15]

Ok well I was going to get you guys some pictures to update on what my tank looked like and my hatch and apparently in the Colorado heat sunny and 84 degrees I opened my gas cap and a good portion of gas soaked me, my keys and my street


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[vannahrose15]

I would send some pictures but it won't let me


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[vannahrose15]

I have a video too but it won't let me embed it


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[Zed Head]

You have to attach them or provide a youtube link.

[vannahrose15]

You have to attach them or provide a youtube link.

I'm also uploading the video to YouTube as soon as that is done I will link the URL thanks guys!



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[Zed Head]

You have the unleaded style, with a little flap that the gas nozzle pushes open.  But air should vent out above the gas nozzle as fuel enters.  Poke the little flap open with a screwdriver and take a look. The sun is at a good angle in your picture.  Take a closeup with the little flap open if you can, might be easier to blow up a picture to see something.