I have a 1973 240Z. A few times I have driven the car until it stumbles and filled it until I see gas in the filler. Only takes 8 gallons. the guage reads 3/4 full. I thought the pickup tube might have a rust hole half way down. I've been told it could be a messed up vent tube. The manual shows 3 from the tank. Fixes?

 

what if you take out the vent lines all together? would this be a problem?

 

Solved my problem by putting a 3/4" vent beside the 1/8" vent at the top of the expansion tank. Pulled out the old vent hose and ran 3/4" tube thru the same hole out of the car. Add a carbon filter and the EPA is happy. Otherwise you will smell gas. While you've got the expansion tank off, blow thru those vent lines to be sure, and they are all necessary because of the shape of the tank and slope of the ground. Make sure they slope up towards the little tank - we don't want gas laying in them blocking the air. I took 7" out of the one under the hatch latch. And I removed 4" from the filler vent hose for the same reason. Observation: Each inch of fuel you see in the filler is about 1 gallon in the tank. 3" = 3gal.



11372-240Z EXP TANK model2 IN top.jpg