Author Topic: I need some help with my fuel tank selector system.  (Read 1145 times)

Offline 1987_Rabbit_Hole

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I need some help with my fuel tank selector system.
« on: September 03, 2021, 06:14:39 PM »
Hey guys,

I bought and am semi-restoring a 1987 V10 Silverado with 350 TBI and dual tanks.  The old man (now passed away) said the tank selector quit working years ago, so he bypassed it and plumbed the left tank directly to the engine.  The plug from the switch harness on the firewall side was was undone and zip-tied to the brake line.  I purchased a new switch and installed it, and plugged the harness back in.  The valve would move, but BARELY and hummed loudly like it was drawing way too much current.  So I went ahead and installed a new valve, new tanks/pumps/sending units, and plumbed everything back to factory.  At first, the truck would only run on the right tank, and would die on the left.  Cleaned and reconnected all the grounds involved, and now the truck will run just fine on either tank.  I can tell the valve is switching, because if I unplug the pump on the side the switch is set to, the truck shuts off.  My problem is, best I can tell, from the GM schematics, the pump in the non-used tank is supposed to shut off, but I swear I can hear them both running all the time.  Also, I don't think the gauge is switching tanks either.  I intentionally put more fuel in one tank than the other so I could watch the gauge, but it just stays on half all the time (probably because they're both getting power somehow).  I have traced the harness all the way, and can't find any unusual looking splices or cuts.  I'm stumped. and I don't want to put my bed back on until I'm sure it's working right and I'm not dead-heading a pump the whole time I'm driving.  One thing I've noticed is the schematic mentions "to rear lighting harness" in a couple of places, and none of that is installed currently.  ANY ideas would be much appreciated. 

Randy