I have a 98 nissan altima. Recently I had problems starting. Determined that it was a fuel issue. Replaced the fuel pump, fuel pump relay, fuel filter and checked the lines for clogs or holes. After all that the car started up great and ran for about a week before it happened again. I just replaced the fuel pump relay this afternoon and it started right up. About four hours later it will not start again. However i'm going to replace it one more time to ensure that this is the issue.

My question is why would this be happening?

Thank you in advance