Does my 79 have a fuel filter in unit?

SirRobyn0

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THANKS, I appreciate the offer. I didn’t know that much fuel is returning from the fuel pump. Thought it was 99% fumes.
If I cap off the return ports on the sending units, I also have to cap the pump port? How much pressure does that return have at the pump, the same as it has to the carb?
I can run the lines, mostly steel. I’d appreciate the rundown when I get there. First need to fix my tank or find another one. This one has leaky pits n a small place under a strap. Been watching vids on de-fuming on YouTube. It’s a small spot.
No it's not fumes in the return line. The vapor line that goes to the charcoal canister is vapor, but the return line off the fuel pump is raw gas. The principle of the system is to keep the gas before the pump moving so it doesn't get a chance to heat up and vapor lock. I do not know the volume of fuel returned in the return line, but I lost a 1/4 tank of fuel in 20 miles, because I had left the return line off the valve one time. I fired it at home and it wasn't until I had to pull up to stop 20 miles later. I smelled the fuel looked at the gauge and knew something wasn't right. Lucky nothing more than some lost fuel occurred.
 

boltbrain

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Wow, sounds like what I do when I can’t wait to try out a thing I’ve been working on. Once I forgot to replace a temporary oil pressure gauge plastic pipe, with copper pipe. Had 200 miles on my own long block rebuild and pulled off the highway so the machine shop could listen to my new engine, saw a line if oil behind me when I parked, 5” wide. That plastic had softened, lost its grip. Was a quart and a half low.
 

SirRobyn0

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Wow, sounds like what I do when I can’t wait to try out a thing I’ve been working on. Once I forgot to replace a temporary oil pressure gauge plastic pipe, with copper pipe. Had 200 miles on my own long block rebuild and pulled off the highway so the machine shop could listen to my new engine, saw a line if oil behind me when I parked, 5” wide. That plastic had softened, lost its grip. Was a quart and a half low.
The thing was in my case I'd replaced a few parts the farm and was short on time and rushed getting it done. I fired up the truck and did a really quick leak check, but I guess I didn't run it long enough for the pump to fill the return line....
 

Rusty Nail

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If I can butt in, I wouldn't modify the fuel return at all. My experience with building drag race cars and messing with vapor return / charcoal canisters has ALWAYS been negative. You are guaranteed to introduce an unknown measure of unpredictability that never sleeps - and that ain't how ya win drag races.

I didnt read this thread but I thought "wtf would you do that for?" Capping off vapor return is bad ju-ju.


Take that for what it's worth - only what ya give for it, but HEY! Who doesnt love unsolicited advice from strangers on the internet, amirite or what?

I said it here - you're asking for trouble.

:imo:

I'd put it back like the General built it.

xc_hide_links_from_guests_guests_error_hide_media
 
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75gmck25

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With a 3 port fuel pump and 3 port sending units you just put a T fitting in to connect both vent lines to the metal line running up to the vapor canister. Each tank’s supply and return lines connect to the 6 port Pollack valve and when you switch to a tank it switches both return and supply to that tank.

You want to keep the return line working because it helps prevent vapor lock in hot weather. When the float shuts off the flow the fuel will return to the tank, and then the pump pulls more cool fuel up from the tank.
 

boltbrain

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With a 3 port fuel pump and 3 port sending units you just put a T fitting in to connect both vent lines to the metal line running up to the vapor canister. Each tank’s supply and return lines connect to the 6 port Pollack valve and when you switch to a tank it switches both return and supply to that tank. You want to keep the return line working because it helps prevent vapor lock in hot weather. When the float shuts off the flow the fuel will return to the tank, and then the pump pulls more cool fuel up from the tank.
With a 3 port fuel pump and 3 port sending units you just put a T fitting in to connect both vent lines to the metal line running up to the vapor canister. Each tank’s supply and return lines connect to the 6 port Pollack valve and when you switch to a tank it switches both return and supply to that tank. You want to keep the return line working because it helps prevent vapor lock in hot weather. When the float shuts off the flow the fuel will return to the tank, and then the pump pulls more cool fuel up from the tank.
With a 3 port fuel pump and 3 port sending units you just put a T fitting in to connect both vent lines to the metal line running up to the vapor canister. Each tank’s supply and return lines connect to the 6 port Pollack valve and when you switch to a tank it switches both return and supply to that tank. You want to keep the return line working because it helps prevent vapor lock in hot weather. When the float shuts off the flow the fuel will return to the tank, and then the pump pulls more cool fuel up from the tank.
With a 3 port fuel pump and 3 port sending units you just put a T fitting in to connect both vent lines to the metal line running up to the vapor canister. Each tank’s supply and return lines connect to the 6 port Pollack valve and when you switch to a tank it switches both return and supply to that tank. You want to keep the return line working because it helps prevent vapor lock in hot weather. When the float shuts off the flow the fuel will return to the tank, and then the pump pulls more cool fuel up from the tank.
No it's not fumes in the return line. The vapor line that goes to the charcoal canister is vapor, but the return line off the fuel pump is raw gas. The principle of the system is to keep the gas before the pump moving so it doesn't get a chance to heat up and vapor lock. I do not know the volume of fuel returned in the return line, but I lost a 1/4 tank of fuel in 20 miles, because I had left the return line off the valve one time. I fired it at home and it wasn't until I had to pull up to stop 20 miles later. I smelled the fuel looked at the gauge and knew something wasn't right. Lucky nothing more than some lost fuel
With a 3 port fuel pump and 3 port sending units you just put a T fitting in to connect both vent lines to the metal line running up to the vapor canister. Each tank’s supply and return lines connect to the 6 port Pollack valve and when you switch to a tank it switches both return and supply to that tank.

You want to keep the return line working because it helps prevent vapor lock in hot weather. When the float shuts off the flow the fuel will return to the tank, and then the pump pulls more cool fuel up from the tank.
Thanks, that’s how I’m planning on doing it, all right, except there are two vapor lines already in place from two tanks up to the engine bay. Also I’m considering going to a single tank between the main rails, and am looking for info on how to do that or if there were any such things from the factory.
 

boltbrain

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Picture the stock fuel filter, Rusty Nail, if you can. it’s got two ports. One pipe port bringing fuel to it, and one square block threaded port to take the pipe going to the carb. That’s how mine has been from the factory 43 years ago. (I rarely send pictures because I only know how to do it from my computer and there’s no internet out here in this rural area). Now picture the same pump with another pipe added. Got it? Pretty simple. Now, I temporarily cap that second port off, and I’m back to where I was. No fuel is returned. After I run a tube from a hose on that new port back to the tank(s), there’s fuel going back to the tanks for the purpose of increasing the flow in order to prevent vapor lock. Now I just wasted time telling you what you could have learned reading the information on previous posts. So now you don’t need a picture. Notice there’s no picture because there’s no need for one.
 

boltbrain

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Here's a picture of the rubber in my gas tank. You can see it split there....Don't work worth a schitt like that.
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Thanks, the one I took out didn’t have rubber on it, Ill try to find one without rubber. But some online sources don’t provide much description.
 

boltbrain

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If I can butt in, I wouldn't modify the fuel return at all. My experience with building drag race cars and messing with vapor return / charcoal canisters has ALWAYS been negative. You are guaranteed to introduce an unknown measure of unpredictability that never sleeps - and that ain't how ya win drag races.

I didnt read this thread but I thought "wtf would you do that for?" Capping off vapor return is bad ju-ju.


Take that for what it's worth - only what ya give for it, but HEY! Who doesnt love unsolicited advice from strangers on the internet, amirite or what?

I said it here - you're asking for trouble.

:imo:

I'd put it back like the General built it.

xc_hide_links_from_guests_guests_error_hide_media
Like I said in my previous post, I’d only be capping off the port or ports that were not there from the factory. The added ports are just carrying fuel, not vapor, back to the tanks. If you read the above posts you’ll know the reason for doing it.
 

Rusty Nail

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Thanks, the one I took out didn’t have rubber on it, Ill try to find one without rubber. But some online sources don’t provide much description.
That's an electric pump what fuels the TBI in my 88. Your 70 whatever is safe.
 

AuroraGirl

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if your original truck had no return, 2 connections that is(inlet and outlet to carb) and you dont want to undergo a swap
get the 3 valve switching thing. Maybe buy 2. the solenoids activate eeach key transition off-on and presumably from crank-run when you start. then anytime you press a switch. that adds up.

if you did have a 6 port, upgrade to the motorized 6 port. no question.

If you dont mind a little extra work you could do a two 3 port switching valves, one that does return and one that does fuel to carb. this would require hooking things up right and other fun things. there could also be a 1 3 port switcher AND 1 3 port manual turn. as long as you remember to turn to return gas to the right tank and mount it to the floor you could make that work... lol!
Then you could also do 6 port motorized but you need to do a bit more plumbing to do that. and make sure its routed good.

if you want to keep your options open you could put a 3 port on the tank and cap the return.

and if you wanted to experiment get a 3 port inline fuel filter and run the 3rd line to one tank but id have no idea how much volume of gas that could possibly return (less than a return line) but mopar did it. they t'ed into a line tho
 

boltbrain

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Ok, good to know, thanks. I’ve also got a 92 K20 Cheyene
if your original truck had no return, 2 connections that is(inlet and outlet to carb) and you dont want to undergo a swap
get the 3 valve switching thing. Maybe buy 2. the solenoids activate eeach key transition off-on and presumably from crank-run when you start. then anytime you press a switch. that adds up.

if you did have a 6 port, upgrade to the motorized 6 port. no question.

If you dont mind a little extra work you could do a two 3 port switching valves, one that does return and one that does fuel to carb. this would require hooking things up right and other fun things. there could also be a 1 3 port switcher AND 1 3 port manual turn. as long as you remember to turn to return gas to the right tank and mount it to the floor you could make that work... lol!
Then you could also do 6 port motorized but you need to do a bit more plumbing to do that. and make sure its routed good.

if you want to keep your options open you could put a 3 port on the tank and cap the return.

and if you wanted to experiment get a 3 port inline fuel filter and run the 3rd line to one tank but id have no idea how much volume of gas that could possibly return (less than a return line) but mopar did it. they t'ed into a line tho
thanks very much. I did think about putting the filter in the return, or did you mean that to be a secondary filter? Becuz it seems like a good idea to have one after the pump.
I’m not afraid of the plumbing but I like reliability and roadside repairability so got a single tank from a 76 Suburban at the wrecker today, which will fit in front of the axle between the channels. The sending unit looks almost identical to the one my dual tank has so it should work with the gauge. I can put tool boxes where the dual tanks are. Under the flatbed.
if your original truck had no return, 2 connections that is(inlet and outlet to carb) and you dont want to undergo a swap
get the 3 valve switching thing. Maybe buy 2. the solenoids activate eeach key transition off-on and presumably from crank-run when you start. then anytime you press a switch. that adds up.

if you did have a 6 port, upgrade to the motorized 6 port. no question.

If you dont mind a little extra work you could do a two 3 port switching valves, one that does return and one that does fuel to carb. this would require hooking things up right and other fun things. there could also be a 1 3 port switcher AND 1 3 port manual turn. as long as you remember to turn to return gas to the right tank and mount it to the floor you could make that work... lol!
Then you could also do 6 port motorized but you need to do a bit more plumbing to do that. and make sure its routed good.

if you want to keep your options open you could put a 3 port on the tank and cap the return.

and if you wanted to experiment get a 3 port inline fuel filter and run the 3rd line to one tank but id have no idea how much volume of gas that could possibly return (less than a return line) but mopar did it. they t'ed into a line tho
Thanks for this great information. Looks like two 3-port valves would work good. I don’t mind plumbing but I got a tank from a wrecking yard today off a 76 Suburban to put between the rails. ( I tried sending another response recently so hope this isn’t a repetition).
It’s a 28 gallon tank and was cheap so am also considering bigger ones. The sender on it is 3 port and is otherwise almost identical to the ones in my duals. I grabbed the two straps too.
 

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