1999 Chevy LT 1500 won't start unless starting fluid is sprayed into intake. Truck runs fine until shut off. What's the cause.

This isn't answer but by 2002 silverado 4.3 does some thing fuel pump is less than yr old and fuel filter is less than 3 months

I started my 2002 4.3 Silverado for 4 months on starter fluid. Depressing Schrader valve (drivers side on aluminum fuel line) had gas shooting out convinced be me no fuel pump or fuel filter problem. Believed either fuel pressure regulator or injectors. Unfortunately regulator is on back of the fuel spider (injector unit) so I replaced fuel spider which comes with a new $12 regulator from PepBoys. The fuel spider/injector unit cost $277. Only found 1 YouTube video on how to do it. Tip: Instead of disconnecting fuel lines at back of bracket take out single 10mm bracket bolt and carefully lift 2 aluminum lines with bracket clear of plenum when you remove it to get to the spider