1987 GMC Sierra Fuel problems

I cant get my truck running.

When you turn key to run do you hear the fuel pump? if so check the fuel pressure with a gauge if its within specs and also for an injection pulses.

When i turn the key on I cant hear the pump come on but it has a fuel tank switch on the dash and you have to depress it full when switching tanks. And if I hold the switch down then turn the key on i can hear it prime but as soon as i release it the truck stops getting fuel

Test the transfer switch

What is the transfer switch and how do you test it

fuel tank switch same as the transfer switch-check and test the fuel pump relay. When you trun ket to run you should be able to hear the fuel pump come on for 2secs-its not happening

I can only hear it come on for a couple seconds when i hold the switch down and turn the key on but if im not holding it down it doesnt come on at all do you think both the fuel pumps are bad ????

You need to determine which pump is coming on and its fuel pressure if its within specs

If i hold the switch on either side i can hear them come on but if i turn the key on without holding the switch down they dont come on at all I dont know if i have the switch wired up wrong or what

Open up the switch and tell me how many wires are going to the switch

There are 4 wires going to the switch I have a test light and only 1 of the wires is hot and its only hot for a few seconds when i turn the key on.. none of the other 3 wires ever make the test light come on I think there is 1 black wire,1 red with white stripe, 1 solid red, and 1 grey wire, And the one wire that is hot for a few seconds is the red with white stripe..