Tank selector valve hose ID help?

[demok83]

Hello all,

The guy that I bought my truck from said the fuel gauge doesn't work and that only the driver side tank is hooked up. I've been researching how to fix the gauge, and took some pics of the tank selector valve. Two of the lines are not connected. Can you guys tell me what lines go where, and what are the two lines that are disconnected? Anybody have any diagrams?

[MountainGoat1966]

My new selector valve came in today, and I was looking at the diagram that came with it and looked at the selector.
The selector itself says R on the housing, and L at the tip away from the selector body.
But according to the diagram, it should be the other way.
We both may find out we need to switch the lines after we hook it up.
The 1/4" line is vent
The 5/16" line is return from the fuel pump.
The 3/8" line is fuel to the fuel pump.
And do yourself a favor, install an inline fuel filter in both lines from the tank before the selector (also voids warranty if filters are not installed).
I wish my scanner would work, I would include a diagram, but I believe one of the other members who has it will be along soon and they can post it for you.

[Just call me Sean]

I would assume each line hooks to the bare nipple they are pointing at. Looks like they bypassed it by hooking them together. But, that's just my assumption. I have to inspect that myself on my truck, the guy I got it from said the passenger side tank doesn't work but I haven't even tried it yet.

[MountainGoat1966]

From the diagram that came with my selector:
Dang it, should have used larger font.
I hope you can read it.

[pontgta]

This should give you a good reference



http://67-72chevytrucks.com/vboard/s...d.php?t=512849


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[demok83]

Dumb question. Why is there a return line? What is its purpose?

[hatzie]

It's supposed to stop vapor lock.
Your lines with the plastic Tee are the vapor cannister lines. They are hooked up all the time.

Looks like the PO bypassed the feed line.

BTW the most common failure is the switch not the valve. Not saying the valve can't be bad but it's way more common for that dash switch to fail.

GM used a momentary switch that returns to center on the 81-86 trucks that says Depress Fully. You need to hold this switch in the position you're switching to for at least 10-15 full seconds.
This is completely unnecessary. The Pollack valve has internal micro-switches and diodes to switch off the valve motor as soon as the shuttle has reached the end of its' travel.
You can, and should, use the 87-91 R/V series TBI switch, AC Delco D7089C, for all 81-91 square trucks. Tell the parts guy you have an '87 with a 350 or 5.7L. The 87-91 R/V series TBI switch doesn't say Depress Fully. It stays switched and works just fine.


↓↓↓↓↓↓↓ Internal switch Schematic of Pollack Motorized Valve A, B, C are gauge switch D, E are the valve motor ↓↓↓↓↓↓↓


↓↓↓↓↓↓↓ Cutaway from the Pollack datasheet showing return and feed nipples ↓↓↓↓↓↓↓

[demok83]

Please forgive me, the truck is a 1983 Silverado with a 350. Thank you for the help guys! I realized that the PO bypassed the tank selector valve altogether. He is drawing fuel from the fuel tank directly to the fuel pump. My guess is that the valve probably failed, and he decided to bypass instead of replace it. Another question, if i might? Where does the return line from the engine come from???? Trying to truly fully understand the fuel delivery system...

[hatzie]

Off the fuel pump.
There are three lines on the fuel pump Supply, Return, and Carburetor.

I'd change the $14 switch before spending $110 on a valve. The valve is expensive and not usually the problem.

[demok83]

Thank you hatzie. I changed the switch last week, and it still doesn't work.