Saddle tank fuel diagram

[Krex]

Any one... Can you help me with the correct and proper way to route my fuel lines with two saddle tanks and a fuel tank in the cab to the mechical fuel pump, I would like it to drain first out of the saddle tanks in the cab tank to make sure my fuel gauge still works at the end of the day .

Thanks everyone for the help

[kwmech]

Normal Saddle tank plumbing dumps fuel into the main line (through the switching valve) until it runs out causing the engine to stumble. Right away you have to manually switch the valve so it catches itself. Unless you install maybe a small electric fuel pump to transfer one one tank to another. And actually there is a problem with these generational tanks being that the fuel comes out of the bottom of the tank. I am working on having my tanks reworked so the the fuel draw becomes a dip tube.

[Krex]

Originally Posted by kwmech

Normal Saddle tank plumbing dumps fuel into the main line (through the switching valve) until it runs out causing the engine to stumble. Right away you have to manually switch the valve so it catches itself. Unless you install maybe a small electric fuel pump to transfer one one tank to another. And actually there is a problem with these generational tanks being that the fuel comes out of the bottom of the tank. I am working on having my tanks reworked so the the fuel draw becomes a dip tube.

thanks i def. need some help here

[jocko]

hope these help - 2nd pic is primary for hose routing - note that the main line to your pump connects to the selector valve at the lowest point on the valve and the upper (higher) three connections are for the main/left/right tanks. It's easier to see if you zoom the pic in your browser. You can't run the lines so that the saddles drain into the cab tank - they all need to connect to your selector valve. There are ways to be able to switch between which tank is being displayed on the gauge, but you have to have senders in all the tanks (not common) and the switching - will add another post for that.

[jocko]

wiring, senders, and switch options. Note, TravelTanks kit shows switch just above right radio knob, but can be mounted wherever you want.

[jocko]

This might help too - just make sure before connecting your lines that you rotate the valve and check to see that the correct part of the valve opens to match the nomenclature on the plate and the particular aux tank line you're connecting. No guarantee all valves are the same, etc.

[Krex]

Awesome I think this will be very helpful, may have questions once I look at the application set up I have, I remember having that fuel connection under the truck. It's a 107 degree in Dallas right now.

[BobS]

I hadn't seen those manual pages before, Thanks for posting them, Jocko!

Bob

[Krex]

Originally Posted by jocko

This might help too - just make sure before connecting your lines that you rotate the valve and check to see that the correct part of the valve opens to match the nomenclature on the plate and the particular aux tank line you're connecting. No guarantee all valves are the same, etc.

Ok I found that I have this same switch under the truck, I found under my bench seat that it goes through the floor, but I have no handle on it to change tanks. Do you have a spare handle for the switch ?

[Cesar Diaz]

FYI I have found new tank valve selector if you need to replace yours at west Marine for only $16.49 plus shipping. Napa charges $89.00 for the same valve.

SIERRA–18-1656 Valve with Detent 3 way 3/8" FNPT Universal $16.49
https://www.westmarine.com/buy/sierr...49?recordNum=7

[jocko]

Cesar, while that valve would work for a factory NL2 setup (driver side aux tank only), note that it will not support saddle tanks (if cab tank is still installed) - you’d need a 3 inlet, 1 outlet valve.

[PbFut]

To be clear, the factory NL2 option on my truck has 2 3 port valves stacked so that the return from the pump is routed to the same tank supplying fuel. One vavle routes supply fuel the other route the return. They are stacked and mechanically sync'd. This eliminates an over fill situation when the aux tank is selected when the main tank is full. And correct, you need a 4 port valve for 3 tanks.

[Steeveedee]

I considered the option of purchasing saddle tanks with gauges, but decided that filling the current saddle tanks and driving 100 miles, then switching to another tank was easier. Just have to keep track, is all. I only use the saddle tanks when towing the travel trailer, anyway. Each tank holds 16 gallons and I get 7 MPG, so there's only going to be a little left. I just rebuilt the carburetor, so maybe my mileage will go up to 8. Woo-Hoo!

[Cesar Diaz]

Sorry yea that is my setup I should have been more specific. The point was those valves are way cheaper at a marine supply. .

[Steeveedee]

Man, where were you when I needed that valve? I paid twice that much off Amazon! I should go buy a spare...

[jocko]

Originally Posted by Cesar Diaz

Sorry yea that is my setup I should have been more specific. The point was those valves are way cheaper at a marine supply. .

No worries Cesar - it’s a great find and thanks for sharing it!! Only wanted to make sure folks looked before they leapt - the same place may also offer 4 port valves at a great price. Thanks again for sharing!

[67RS/SSx2]

Okay, not to hijack this thread (really this is a complete hijack of this thread ) but does anyone have a source for the valve including fuel return lines? I need something for my '72 with the NL2 option I am trying to put back together.

A previous owner changed to an electric valve which no longer works.

Thanks!

[jocko]

In post # 10 Cesar shared a link that could work - but recommend read the 2 reviews and decide for yourself (almost sounds like something was wrong, as in defective with THAT one valve, with the valve that got the negative review). The price sure is right.

[67RS/SSx2]

The valve in post #10 does not have capabilities for tank return lines. I found this one https://www.westmarine.com/buy/groco...55?recordNum=5 but it sure is pricey ($190) and I am not yet certain it would fit in place of the original.

[jocko]

Post #6 is from a dealer-installed saddle tank system on my 72 K20 and has no return lines routed through the selector valve (and I realize you are asking about a factory NL2 system, which is different than dealer installed stuff). I only have 71 dated Assembly Manual references for line routing, but it only shows a 3 port valve for the NL2 RPO (but the fuel system changed a little in 72, so not a totally applicable reference either). Below is the best pic I have of my 72 C20 NL2 setup, and you can see there are only 3 lines present (kinda hard to see). I would assume the 72 return line would simply go to the main cab tank regardless of tank selection, but I don't have a diagram to prove it and no longer have the C20 NL2 truck to walk out to the garage and check - so, this may not be much help! But, I don't recall seeing a return line routed through the selector valve on any of the multi-tank 72s I've owned, either NL2 or aftermarket saddle tanks.

[67RS/SSx2]

I think you can see the return line connection on my aux tank in the attached pic. I cannot imagine connecting a single return line to the main tank when multiple tanks exist. In my case if both tanks were full and I select the aux tank, the returning fuel would overflow the main tank and I would expect fume issues. Not to mention the aux tank would drain much faster if returning fuel was going to another tank.

I looked in the assembly manual. It does not show a fuel return system for the aux tank but it is only marked as 1971. Don't know if there would be any difference in a 1972 version. I also looked in my GM parts book but nothing difinitive there either.

Pbfut mentions the return line valve in post 12. Interesting...did some have return lines (and return line valves for aux tank) and some not? My truck has a 400 engine and was built in California. Wonder if any of that makes any difference?

Also attached a pic of the electric fuel switchover valve that was added to my truck. I do not have the original manual valve. You can see it switches the return line.

As usual I am all questions and no answers!

[Steeveedee]

Your saddle tank has a pipe next to the fill pipe, which mine does not have. I suspect that it is a vent pipe. If so, where did it lead to? Mine has vented caps. Fremont build, 402 engine, no idea who installed the saddle tanks, as the truck came into my wife's family in '73. It has a PCV as the entirety of its pollution controls, unless one counts ported spark. I just went and looked. There is a thermostatic valve on the intake snorkel. That valve switched from a pipe that was mounted on a shroud on the exhaust manifold to heat the carburetor and get the choke open sooner. Only the valve in the snorkel remains. It's been that way since I met my wife-to-be, in 1980.