ezcruiser Posted March 31, 2009 Report Share Posted March 31, 2009 I was looking for ventilation hose routing for my gas tank and I opened up my chiltons to the 1970-1980 fuel system diagram to reveal missing direction lines pointing to where the hoses connect. I believe it was just a misprint because several things didn't come out too clear on this page. Would anyone take a picture of theirs so I can connect the dots on mine? Thanks! Quote Link to comment
djmoreron Posted March 31, 2009 Report Share Posted March 31, 2009 im testing out my new scanner. heres the fuel diagram i have in my haynes manual. i think its the same as yours, my scanner barely picked up the direction lines, even after messing with the settings. hope this helps. Quote Link to comment
Llittle_Llama Posted March 31, 2009 Report Share Posted March 31, 2009 my truck had no reservoir :confused: Quote Link to comment
djmoreron Posted March 31, 2009 Report Share Posted March 31, 2009 you know what, the lines werent that clear in my book to begin with, so thats why they look so bad. im getting the fsm tomorrow in the mail, so ill double check then. Either way, heres the same scan with the colors inverted. hope it helps... Quote Link to comment
ezcruiser Posted March 31, 2009 Author Report Share Posted March 31, 2009 Thanks a bunch DJM! Yeah it helped out some! I'm gonna draw them with a pencil for right now, I'll wait on your fsm too if you think you may post up a pic of it!!! Thanks again!:) Quote Link to comment
Z-train Posted March 31, 2009 Report Share Posted March 31, 2009 my truck had no reservoir :confused: Might be a Peoples Republic of Kalifornia model thing.:rolleyes: Quote Link to comment
Llittle_Llama Posted April 1, 2009 Report Share Posted April 1, 2009 Might be a Peoples Republic of Kalifornia model thing.:rolleyes: lol, are not all 620's from cali?!? lol Quote Link to comment
lynchfourtwenty Posted April 1, 2009 Report Share Posted April 1, 2009 if i had the money i'd pay someone to put my damn tank where it belongs.. im tired of it sittin in the bed :( Quote Link to comment
djmoreron Posted April 3, 2009 Report Share Posted April 3, 2009 Here is the First pic from the 1977 FSM and another that may be helpful.... got em both in pdf format too http://www.mediafire.com/?2nmunwzdkmy 1 Quote Link to comment
Rubberman Posted April 3, 2009 Report Share Posted April 3, 2009 Thanks ez and dj, this is what I've been needing. Quote Link to comment
bluebird4200 Posted July 27, 2014 Report Share Posted July 27, 2014 Looks like I have the same fuel tank as the first diagram. Did you guys figure out which inlet at the top of the tank is the return line? I just drained my tank, and was about to uninstall it so that I can figure that out. Any input? Quote Link to comment
bluebird4200 Posted July 28, 2014 Report Share Posted July 28, 2014 there is no return line. The top 2 inlets are vents...sucks ass if you have a late 74'. Quote Link to comment
wayno Posted July 28, 2014 Report Share Posted July 28, 2014 I turned my late 521 tank emissions vent into a return line. Quote Link to comment
DanielC Posted July 28, 2014 Report Share Posted July 28, 2014 My latest build date 521 was made 04/70. It does have the evaporative emissions tank on it. The filler neck has a place for a 1/4 inch hose, and a 5/8 Inch hose, and the big hose to fill the gas tank. The gas tank has a place for the 5/8 inch hose. Use a 5/8 inch hose to connect the two together. Boats use a 5/8 hose to vent the gas tank, if you cannot find the hose at an auto parts store. The vapor recovery tank has three connections on it, all 1/4 inch. The one on the side of the tank goes to the filler neck. The lowest hose connection in the bottom of the vapor separator tank goes to a 1/4 connection on the gas tank. The remaining connection on the vapor separator tank goes to the engine compartment. Obviously, the big hose connection on the filler neck goes to the big hose connection on the gas tank. There is this valve in the engine compartment. You will notice it has three letter by the ports on the valve. "A" , "F", "C". from the top on the valve. "A" goes to the underside of the air cleaner. "F" goes back to the vapor recovery tank. "C" goes to a small tube on the side of the larger PCV tube coming out of the crankcase of the engine. Air or vapors can flow down in the valve. The gas tank vents through the vapor recovery tank, the valve, to the air cleaner when there is a vacuum in the tank. When there is pressure in the tank, the pressure goes through the vapor recovery tank, through the valve, and into the crankcase pipe of the engine. If the engine is running, the PCV system sucks the gas vapors into the intake manifold, through the PCV valve. If the engine is not running, the gas vapors are collected in the crankcase of the engine. Evaporative emissions are a good thing to control. It does not cost you any power. It returns vapors back to the separator tank, hopefully some vapors condense back to liquid, and return to the gas tank. Some vapors are fed back in to the engine, when it is first started, when the engine needs a richer mixture any way. Quote Link to comment
Pacific coast Datsun Posted July 29, 2014 Report Share Posted July 29, 2014 My 74 has the 2 vent ports on the gas tank too but both are plugged. Im wanting to install a return line to fix a vapor lock issue. Can i use one of the vent ports as wayno did ? Quote Link to comment
wayno Posted July 29, 2014 Report Share Posted July 29, 2014 I got rid of the vapor emissions recovery tank years ago, I have been using that fitting on the top of the tank for the fuel return since then without any issues. I got rid of the recovery system when I went to a flatbed, I did not remove it because I thought it was bad or anything, it just happen to work out that way, I needed a return line fitting on the tank, and I needed a return line also. Before I removed the 521 bed I was using that vapor recovery line to return the fuel anyway, but I put a tee in that 5/8ths vent line going to the fuel filler hose, so when the engine was running I could take the gas cap off and see fuel being returned, but I changed a lot of things when I made the flatbed. Quote Link to comment
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