Tank selector switch problem?

[87chevyguy]

I have an 87 silvrerado with a tbi 305. It has dual tanks and is stock except for open element air cleaner and aftermarket muffler. Has 67k miles and was taken very good care of by previous owner. Yesterday I filled up both tanks at the gas station and started the truck. I pushed the switch to go from right tank to left tank and it sputtered a couple times and died. Got it towed home. I couldnt hear either pump run so I messed with the switch and I could get it to run on the left side only. But when it cranks it idles extremely rough and dies very quickly. Can't give it has to keep it running. It was running fine before that. I ordered a new switch and I'm going to change it when it gets here also changed fuel filter today and while I was under the truck I unplugged the switch valve and gas was all inside the connector so I'm not sure if that is the problem or the switch. Any help would be greatly appreciated. Thanks

[bd]

...I unplugged the switch valve and gas was all inside the connector....

At the very least you have a bad selector valve.   

[bake74]

     Trace power from the switch on the dash board back to the selector valve under your cab. 
  http://forum.73-87chevytrucks.com/smforum/index.php/topic,22933.msg189901.html#msg189901    here is a good link that explains how the selector valve works and I won't have to type it all out (see the last entry).  Also make sure you have a good ground on all the componets, grounds are very important and mostly the cause of problems with these trucks.
     Keep us informed of your progress.

[Captkaos]

How long have you had the truck?  Which side was it on prior to switching?  Have you ever used the opposite side?  If not do you know the state of the gas?  If one side is working and the other isn't, your switch needs attention.   I suggest pulling it apart and cleaning it:
http://forum.73-87chevytrucks.com/smforum/index.php/topic,6537.0.html

[87chevyguy]

I have had the truck for about a year. It was on the right side prior to switching then mashed left and it died. Got the new switch today and threw it in. The truck cranked right up and runs like it did before. A little boggy and kind of sluggish like something is holding it back. But I haven't done a tune up yet so that may be it and I will deffinately change the switch valve as I call it to stop the leaking inside the connector. Thanks for yalls help.

[78 Chevyrado]

Almost every time I have had a dual tank switching failure, it was the switch itself.  But the switch wasnt bad, just dirty.  On mine  They used some kind of foam in the switch to keep dust n such out of it, and in every one I've taken apart the foam had disintegrated and was sitting on the contacts keeping them fron touching.  So I took the switch apart, cleaned the foam out and was back on the road.

[VileZambonie]

The Tbi switch is different than the carbureted switch and the tbi switch rarely goes bad. It's probably just a faulty selector valve.

[frotosride]

 The actual switch, where you press it up or down, just has a piece of plastic that moves the actual terminal. It will wear out... I found that an early sign of it weraing out was having to hold the key over a little longer as well as it eventually not allowing me to use the right  tank.  The switch works rather simply. when it is in the down position it energiges the selector valve and shifts to the left tank. When in the up position it is de-energized and opens to the right tank.
I had this same instance happen to me just a few weeks ago.

[1979C20]

Is there any possibility there was bad gas in one of the tanks and your truck is running like bad because of it?

[87chevyguy]

I was going to try cleaning the switch but I never could figure out how to get it apart so I just got a new one. I don't think it has bad gas in either because they both worked normally before and still do now. I use both tanks on a regular basis. It may need a tune up, it may be vaccuum leak, I have also heard that it sounds like my advance is not working because I have a big hesitation. I consistently get 12 to 13 mpg with 2.73 rearend and th400 trans. Which is not good I don't think but I don't drive to much so it's ok.

[VileZambonie]

The actual switch, where you press it up or down, just has a piece of plastic that moves the actual terminal. It will wear out... I found that an early sign of it weraing out was having to hold the key over a little longer as well as it eventually not allowing me to use the right  tank.  The switch works rather simply. when it is in the down position it energiges the selector valve and shifts to the left tank. When in the up position it is de-energized and opens to the right tank.
I had this same instance happen to me just a few weeks ago.

The TBI switch is NOT the same as a carburetted switch. You do not depress and hold it's simply up and down.

[bake74]

I was going to try cleaning the switch but I never could figure out how to get it apart so I just got a new one.

     Some times on certain electronic components it's just not worth it to take apart and clean.  Once opened they require cleaning all the time because of dust invasion and such. 
     I think these switches is one of those circumstances, they are cheap and really easy to change out, and you have piece of mind after that .

[VileZambonie]

Oh, and i didn't know that some TBI switches have to be held

That's not what I said.

[frotosride]

Thanks, I'm trying to soak all of this up and learn.