87 dual tank prob

[mike allsbrook]

Hello I'm new here and hoping I can find some solution to my problem with 1987 c10,it has dual tank system throttle body fi v8.....I have no power to the tank selection dash switch,4 wire switch...truck will not run,tries to start and dies no power,figured I would replace selectee switch same deal,checked for 12v at pigtail ,none with key to on position...connector has 4 wires...a black b grey c tan white d tan..I think black would be a ground? What wire should be 12 v when ign switch at on and where is it supplied from,any help would be appreciated
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[mike allsbrook]

Originally Posted by mike allsbrook

Hello I'm new here and hoping I can find some solution to my problem with 1987 c10,it has dual tank system throttle body fi v8.....I have no power to the tank selection dash switch,4 wire switch...truck will not run,tries to start and dies no power,figured I would replace selectee switch same deal,checked for 12v at pigtail ,none with key to on position...connector has 4 wires...a black b grey c tan white d tan..I think black would be a ground? What wire should be 12 v when ign switch at on and where is it supplied from,any help would be appreciated
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[mike allsbrook]

I have also checked all fuses,can't find anything on power distribution....
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[44th Miss Inf]

My wiring to my switch is pink, black, lt green and dark green. The pink goes to ignition hot, black to ground, then greens thru firewall to tank selector. By that, I would check you grey to see if it goes to a key on source in the fuse block and check the black has a good ground. Double check your wiring though, but I'm thinking your grey should be your "hot" wire
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[mike allsbrook]

Originally Posted by 44th Miss Inf

My wiring to my switch is pink, black, lt green and dark green. The pink goes to ignition hot, black to ground, then greens thru firewall to tank selector. By that, I would check you grey to see if it goes to a key on source in the fuse block and check the black has a good ground. Double check your wiring though, but I'm thinking your grey should be your "hot" wire
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Appreciate it bro,just got off phone width my local dealership and parts guy is going to try to find me a schematic,everything I have found shows dif color wires at tank select switch...I'm getting closer
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[44th Miss Inf]

Sorry, forgot 87 has pumps in the tank, and my truck doesn't

This should be the proper schematic for the 87 I believe
By this grey goes to right side of selector, tan to left and tan/ white to fuel pump relay/fuel module
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[Gordonr1973]

Your motors dying because the fuel pump isn't engaged.

With TBI, the switch isn't always on left or right like a carbed motor...it just should toggle left or right and then come back to it's resting position.

In these trucks, 99% of the time, black wires are ground.

The diagram 44th posted looks correct, post back to say if you've figured it out.

If you have access to a Haynes manual, buy one.