on my 90 v3500 the left tank dose not work.I've replaced both fuel pumps,switch on the dash,switch over under truck,and pulled out alot of my hair.still nothing from the left side.If I supply power to the pump it runs.just not through the truck wiring.I tested cont. all the way to the pump and it's good.

according to the wiring diagram power runs through the oil pressure switch.is this the same on the guage works off of? if not where is this on located.ny switch is ion the back of the block with 3 wires.the diagram says it only has 2.

Also truck is a 1990 GMC V3500 crew cab 1 ton 4x4.5.7l.(350C.I.D.)auto trans(Turbo 400).all stock.

Ok figred it out relay was wrong.now I have no injector pulse(ie no fuel spray from injectors from left tank.right is perfect.Please help.