Solenoid tank selector valve

[mybigtruck]

Got a 79 K 20 with dual tanks. The AUX tank has not been used in years. I am currently trying to see if it can be used. I get 12 volts to the connector that attaches to the valve, when the switch is set to the AUX tank position. When I connect it to the valve there is a slight clicking noise. This makes me think the valve is switching but I am not sure. How much noise should the valve make? Should it be an audible "Thunk" or just a little bit of a click like I am hearing? Any suggestions for a test to be certain if the valve has switched? All I can think of is to get the truck running and switch to the AUX tank. If it switches then the engine should continue to run and, of course, it will die if it does not switch. Anyone have any better ideas than this?

THX for any and all help.

[78trk]

With 12 volts my 78 opens up the pass side fuel tank. Take off the lines from the valve. hook up a piece of fuel line to the pass side fitting on the valve and blow. You should get air on the fuel pump side of the valve with 12 volts on the valve. Without 12 volts you should get air to the fuel pump side when you blow on the driver side of the valve.

[Dead Parrot]

Don't trust the several year old stuff in the Aux tank to still be good fuel. It may well have rust, water and decayed gas in it. It could turn an otherwise working fuel system into a multi-day repair project.

Another way to check the valve is to disconnect the Aux side of the valve, connect a piece of 3/8 gas hose long enough to be in a small can of gas, less then a pint. Start the truck, switch to Aux, if the can slowly empties, valve is good.

[mybigtruck]

Good suggestions. THX for the quick reply's.

Two more questions: Will I have to worry about a lot of fuel draining from the disconnected lines or does it only flow when pump is drawing and what is the best way to get the old fuel out of the tank? I have a shaker siphon but it doesn't work after trying to snake it down the fill opening. Is there a hose or plug that I can use to get the fuel out.

One again, THX for any help.

mybidtruck

[badchevy]

I say the best way to drain the fuel out of the tank is to drop the tank. I tried siphoning mine out but it still left some fuel in there. My truck also sat for about 4 years and one of the tanks was nasty in the inside. Already dropped it twice and it still not thoroughly clean. I will be replacing that tank in the near future. You only need to unbolt 8 bolts (hold the L-brackets that hold the tank) which are located inside the frame rail. Then it's a couple of fuel hoses, electrical connector, 2 ground wires, and 3 Phillips screws (fuel neck). Hope I make sense with this and good luck.

[clapage6]

As mentioned the best way would be to drop the tank but to just get rid of the fuel that's in there you can locate your feed and return lines from the tank..... Put your feed line into a bucket/pan/gas can etc wherever you want your fuel to drain, then apply low pressure to the feed line into the tank. Even just blowing into it would be enough to start draining. Male sure to keep the cap on snug also during this process.
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[mybigtruck]

Good suggestions.

I'll have to drop the tank at some point anyway. The wire to the gauge sender is broken all the way up at the top where it is supposed to attach to the sender. To fix it I'll have to have the tank down. I'm just worried that a tank with much fuel is going to be heavy. I have a compressor so I like the idea of using it to start the fuel out of the feed line. Am I correct in thinking that once I get it started the fuel should siphon out through the feed line as long as I keep the catch can lower than the bottom of the tank?

THX

mybigtruck