5veinte1 Posted October 17, 2017 Report Share Posted October 17, 2017 Does it need to be there? I have never seen something like it, and I would like to eliminate it if possible. 1 Quote Link to comment
wayno Posted October 17, 2017 Report Share Posted October 17, 2017 I removed mine and used the fitting on the tank for the fuel return line. 2 Quote Link to comment
DanielC Posted October 18, 2017 Report Share Posted October 18, 2017 It is not an expansion tank. It is a liquid-vapor separator, and is part of evaporative emission control system. There is a three port valve in the engine compartment, by the carburetor. This valve has a connection to the air cleaner, the engine crankcase, and the upper connection on the separator. There are three letters on the flow control valve, "A" "F" "C". "A" goes to the Air cleaner underside. "F" goes to the upper port on the separator. "C" goes to the Crankcase. Air can flow from the air cleaner, as the gas tank empties. If pressure builds up in the gas tank, engine off, the air and fumes are pushed into the engine crankcase for storage. With the engine running, the PCV system removes the fumes from the engine crankcase, and into the intake manifold. Evaporative emission controls do not rob any horsepower from the engine. Evaporative emission controls stop raw gas fumes from escaping away from the vehicle, this is a good thing. It may even increase your gas mileage slightly. I would suggest leaving it in place. 3 Quote Link to comment
mklotz70 Posted October 18, 2017 Report Share Posted October 18, 2017 You're in CA.....removing it will depend on whether you need to go through emissions testing or not. Rigs this old are typically exempt, but the rules vary state to state. 1 Quote Link to comment
5veinte1 Posted October 18, 2017 Author Report Share Posted October 18, 2017 Smog here is 1975 and older. I don't have the valve in the engine compartment DanielC mentioned that I can see. The fuel return is disconnected and capped both in the engine bay and at the tank location. Currently I have the bed off on my hoist installing the tank. Is the return necessary? It looks like it would have to run across the engine from the carb to get back to the tank, and that seems weird to me. I know on my other truck Soy there is a little silver thing that is held in the bracket on the passenger side of the engine bay. I don't have pictures of that truck but here is what Wasabi has: 1 Quote Link to comment
5veinte1 Posted October 18, 2017 Author Report Share Posted October 18, 2017 BTW I really, really need an L18 timing indicator. 1 Quote Link to comment
5veinte1 Posted October 18, 2017 Author Report Share Posted October 18, 2017 Correction, L16. Sorry. 1 Quote Link to comment
wayno Posted October 18, 2017 Report Share Posted October 18, 2017 You don't have to have a return line, but my SUs had one so I used that hard line as the return line and I routed the other end of that hard line straight to the tank fitting for the emissions stuff bypassing the small emissions tank. 1 Quote Link to comment
5veinte1 Posted October 18, 2017 Author Report Share Posted October 18, 2017 That good intel, thanks! 1 Quote Link to comment
banzai510(hainz) Posted October 18, 2017 Report Share Posted October 18, 2017 I dont run return lines on my Datsuns. The mechanical pump goes limp when the carb has its bowl full. I see your gas line is on the otherside. Hope you have fuel filters as 521s pick up alot of dirt in the tank from the fuel hose in the wheelwell. you could just use a ink pen mark to mark TDC on the timming cover. its close to where that bolt hole will be. then use a stick or visually see the piston at the tiop and look at the timming sprocket lined up and assume your at TDC then mark the front cover. then use the indents on the crank for the BTDC using a light. SIMPLE. Cant tell if your running points or a elelctric distributor. as zi dont see a ballast resisitor. so I assume you have a 3 ohm coil for a Pertronix or your electric matchbox dizzy. Long as it works for you. just ck if coil is HOT to the touch then you know you have a possible proplem. 1 Quote Link to comment
thisismatt Posted October 18, 2017 Report Share Posted October 18, 2017 Three things in life are certain: Death, taxes, and hainz spelling timing timming 4 Quote Link to comment
datsunaholic Posted October 18, 2017 Report Share Posted October 18, 2017 Webers like return lines. In my case they've eliminated the need for a fuel pressure regulator. 1 Quote Link to comment
5veinte1 Posted October 19, 2017 Author Report Share Posted October 19, 2017 So I ordered a fuel filter yesterday because fuel filter. Thank you for the redemption on the purchase. hainz, I apologize in advance for my ignorance, but what you said about the timing I don't understand. As I mentioned in another thread what I don't know about this could fill a book. I was told the distributor and ignition were electronic. God I hate not knowing shit I should know about shit I own! 1 Quote Link to comment
banzai510(hainz) Posted October 19, 2017 Report Share Posted October 19, 2017 well watch my vids and look at my timming pointer on my motor and just a ink pen instead as a general guidance. stock fuel pumps dont need a fuel pressure regulator so I never have ran a return line. plus my 521 never had one 1 Quote Link to comment
datzenmike Posted October 19, 2017 Report Share Posted October 19, 2017 The return line has a small restriction near the engine. The restriction allows the pump to build pressure so gas will flow into the carb and not all back into the rank. The hole isn't very large (larger than a pin hole) and allows some gas to return to the tank. I think all L20Bs have it because they run hotter under the hood and can suffer from vapor lock and hard restarts. The return constantly empties the fuel line near the carb of over heated fuel and any vapors from boiling and replaces it with cold fuel from the tank. The return also vents any left over pressure back into the tank when the engine is shut off. The thing I like best is ALL the fuel eventually gets circulated. This means ALL fuel is filtered over and over, removing any crap in it, keeping the tank cleaner. 1 Quote Link to comment
wayno Posted October 19, 2017 Report Share Posted October 19, 2017 I like return lines because of the heat issue Mike just described, cool fuel in the lines. I actually have a stock regulator on the back SU(or I did until I changed SUs), if it starts vapor locking I will have to transfer the regulator to the SUs on the engine now, but only have them issues in the summer when it is hot out, it is cool now. I also have an electric fuel pump now(last few years), as sometimes when I parked the truck on a hill(front pointed up hill) and the engine stopped in just the right spot, the fuel would siphon back into the tank and I could not keep the engine running on the fuel in the bowls, it would die and would not start unless I used a screwdriver on the fuel pump arm to get the fuel back up from the tank, I believe the fuel pump had a small hole/crack in the diaphragm and it would not suck the fuel up from the tank when it was very hot out, but that little extra movement in the arm that it didn't get to while running was enough to pump the fuel out of the tank, it finally got so bad I converted over to an electric fuel pump. 1 Quote Link to comment
Stoffregen Motorsports Posted October 19, 2017 Report Share Posted October 19, 2017 Timming. Isn't he from South Park? 1 Quote Link to comment
DanielC Posted October 19, 2017 Report Share Posted October 19, 2017 On a 521, the line from the flow control valve to the vapor separator tank is not a return line for liquid gasoline. It is to vent air from the air cleaner, through the flow control valve into the gas tank as the pressure in side the tank drops as gas is used up. 1 Quote Link to comment
gene knight Posted October 21, 2017 Report Share Posted October 21, 2017 I removed mine on grimace and I am running a weber/canon intake Quote Link to comment
mrbigtanker Posted October 21, 2017 Report Share Posted October 21, 2017 Rip that shit out and throw it off the tallest mountain. Like Daniel C said not a bad thing but even in california its not needed. Good place under that cover to mount a small odysse battery. :thumbup: Quote Link to comment
5veinte1 Posted October 21, 2017 Author Report Share Posted October 21, 2017 Thanks to everyone for the advice. I'm taking it out and running a more conventional setup. Why make it harder than it has to be? In my experience, more parts=more chances for failure. Quote Link to comment
DanielC Posted October 21, 2017 Report Share Posted October 21, 2017 Make sure the gas tank is vented some way. Quote Link to comment
mrbigtanker Posted October 22, 2017 Report Share Posted October 22, 2017 I use the fuel regulator return to the old vent line. Quote Link to comment
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