6 port fuel tank switch valve....How to check?

[Paladin]

Ok, so I have this thing out and want to check it for proper function before reinstalling it. I have an extra pigtail for it so testing it on the bench with power if need be should be no problem. Can anybody tell me the proper way to check this thing to prove it is good or needs to be replaced? If it is bad I am thinking of just eliminating it completely and rig the tank lines up to a manual valve where I can just slide under it and switch tanks manually. I'm tired of screwing with this **** and want to fix it one way or the other. Anybody have any suggestions on the later idea as well?

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[wanderinthru]

I have just always replaced them with a manual valve, generally mounted thru the floor on the trans hump.

 

[bedwards]

I took my gas caps off. I shot compressed air through the line from where it connects at the fuel pump and listened for the bubbles in the tank. Then switched tanks and did it again for the other tank. Blew the vent line out the same way.

 

[Grit dog]

Well idk the wiring pin outs but I believe there’s only 1 power wire to the valve, the others are the fuel gauges?
If you know which ports go to what, when no power to valve, it defaults to one tank. Driver side I believe so you should be able to blow thru drivers side inlet to outlet and not passenger side.
Power to valve pin, should be able to blow through pass side inlet to outlet.
Same for return ports.
I’m speculating because Maybe I lucky. The 34 year old truck we got this year works perfectly and I never had cause to replace one back in the day on any square at home or work.
Knock on wood

 

[eskimomann209]

I believe port closest to mounting nuts is the ground. Second and third pin alternate tanks. Provide power to each one individually to cycle tanks. Blow in the “fuel discharge” to see what fuel port it blows out of. Cycle blow again make sure it’s switched.

Fourth is one tank sender. Fifth is to fuel gauge. Sixth is to other tank sender.
I’m fairly sure that’s now mines setup.

Edit.*
If buying new or determining this one is good. Make sure the new one has fuel filters between the tanks and the pollak valve. Grit in the valve helps jam things up quicker.

 

[Grit dog]

^So the newer style valves are not default to one tank with no power?

 

[eskimomann209]

They remain on the tank last selected.

^So the newer style valves are not default to one tank with no power?

 

[Grit dog]

Makes sense Eskimo.
@Paladin , there are a multitude of wiring diagrams if you just google it. Pretty easy to follow with the diagram.

 

[Dave M]

Here's a link to a previous thread which might be of some help.


https://www.gmsquarebody.com/threads/dual-tank-operation.20921/