fuel return line?

[jveik]

Sorry if someone already had a post about this issue, but i still dont quite understand how i should go about hooking up my fuel lines.

im gonna be running an older style smallblock with the fuel pump on the block feeding around 7psi to the carb, and if I remember correctly, the only fuel line that was hooked up before was the main fuel line to the pump. my truck has a total of 3 metal lines on the frame rails (main fuel line to pump, return line to tank, and vapor line to vapor canister). is the fuel pump designed so that if there is enough pressure that it lets some bleed back into the line that feeds it?

my point here lol is that i dont know what i should do. will i be ok if i just run the line to the fuel pump and call it good? do i have to run a return line and if so, how do i hook it up and to what do i hook it up? also, for the vapor line, the canister vacuum tube was never hooked up anyways, so should i just let the line empty vapors into the engine compartment, or would it likely cause an explosion? Any light shed on this confusion will be greatly appreciated.

[777stickman]

What truck are you working on??

You don't need a return line with a block mounted pump. Just like you said what would you hook it up to. As far as the evap canister I would hook it up as it came stock. That system just takes tank vapors and runs them back thru the motor. If you plug it up you could have issues with tank venting.

By the way, what the hell does "lol" mean?? ............Steve

[jveik]

yeah "lol" stands for "laugh out loud" and back when i was about 12, or about 7ish years ago, i used to use instant message or whatever it was called to talk to friends from school and whatnot and basically i used it without even realizing it. i try to not use it but i dont even think about it and am too lazy to edit a post to remove the goddam "lol's". as for the fuel line issue... it the vapor line should be ok if I just let it sit hooked up to the canister and whatnot? my dad was moving some of my parts around (when youre 18 living at home still, you tend to not care where you set stuff down) and he broke the little deal on the top of it where you put a vacuum line to the carb. i dont want to cough up 50 bucks for another one and i couldnt find any at my local junkyards either, so could i just let the line empty vapors into the open air or would a spark cause an explosion? i dont really mind loosing 10 cents worth of gas vapors a day or whatever it would loose.

[jveik]

its a 73 by the way...

[Blue Bowtie]

The return line from the pump was an early GM attempt at eliminating vapor lock. The three=line fuel pump would have an internal pressure relief valve fixed at about 5-6 PSIG, and the pump would try to pump full volume all the time. This would keep the pump and lines cooler since the volume flowing from the (cooler) tank would always be higher, and fuel would not linger in the pump supply line nor the pump long enough to heat and create a vapor lock. You don't need to use it, and shouldn't if you don't have a three-line fuel pump. Just plug the unused return line.

As for the vapor line, it would be safer to plug/cap the line rather than allow it to vent into the engine compartment. It would really be best to connect it to a vapor canister and enable the purge through a TVS and timed vacuum port on the carburetor - The way it was done originally. Beyond the emissions factor, you can lose about 7% of your fuel within a week in warmer temperatures just by evaporation. Without collecting and burning it later, you might just as well roll up and burn a $10 bill every time you fill your tank.

[fuzzypuppy]

You could repair the evap canister, a hardware store should have brass fittings that have threads on one end and a barb or hose end on the other, use one of these to replace the barb broken off the canister.
there are also plastic fittings like this, both can be found in the plumbing section, just get a little creative.

[jveik]

but if i needed to be a redneck i could just plug that mofo up with something then eh? that might be the way to go for me. its not a mileage issue that much anyways, since ill be getting single digits in the city even if I'm lucky. i actually am planning on buying a new gas tank off of LMC Truck, so maybe ill get a new sending unit that doesnt have 3 different lines coming off of it to stick in there.

if i get a new sending unit, will it still function the same as my original in terms of accurately telling me how much fuel is left or would it be out of calibration?