I bought the check valve on Ebay. I put it on the feed line as close to the tank as I could get it. Make sure it is rated for gasoline and the hoses to connect it are rated gasoline for fuel injection.

 

I installed a check valve on a 2008 Suburban 5.3 vin J and found that the fuel rails will continue to build fuel pressure after engine is shut off due to heat absorption. This system is a non fuel return design and will not start with excessive fuel pressure. My fuel pressure gauge read 100+psi (pegged the fuel gauge).
I removed the check valve and installed a Bosch fuel pump to eliminate the hard start problem. The pump that was causing the hard start was an aftermarket Airtex pump module assembly. I bench tested the new Bosch pump. Blowing (with mouth) air backward through fuel line and no air can go through but I could blow back through the Airtex pump.