Dual tank fuel problem

[Txsilverado87]

87 r10 duel  tank, new switch on dash,passenger side tank working,nothing on the driver side,if I set the switch to the non working tank and selector valve is working I should have power to the fuel pump,right..?.I don't know much about this,any help on this out there

[Captkaos]

There is a test port on the firewall and the fuel pump relay.  You should be able to supply power to that and switch tanks and the appropriate pump run with power applied.

[Irish_Alley]

There is a test port on the firewall and the fuel pump relay.  You should be able to supply power to that and switch tanks and the appropriate pump run with power applied.

the test port is a 3" red wire with a female connection. apply 12v from your battery and the pump will turn on if its good. but i think it only bypasses the relay since it still has to go through the switch to determine what pump to energizes. i believe you have to test the wire at the pump to see if its getting power. might be able to test it also at the selector switch but i cant help you on what wire it should be

[Txsilverado87]

If anyone out there can explain or upload info on how the fuel tank switch valve works would be great,if the valve is bad then why would the passenger tank be working,is the test port suppling power to the switch valve or bypassing it

[Irish_Alley]

maybe its the pump in the one side is bad. im pretty sure it just bypasses the relay or when you do use the test wire it would energize both pumps