04 intermittent no start

I have an 04 Impala 3.4 with 126000 miles that will intermittently not start. It cranks fine but will not start. When I turn the key, I do not hear the fuel pump prime. There are no warning light, i.e. service engine, security. It will not start with starting fluid when this happens. I can pull the fuel pump relay out and put a jumper wire in its place and it will start right up every single time. Weather/temperature doesn't seem to make a difference as to when this happens. It happens after sitting overnight and it might happen after only sitting a few minutes. I've switched out the fuel pump relay so that's not the problem. I've replaced the crank position sensor and the fuel pump. This problem happened earlier this year and I unplugged the computer for a little while and that seemed to fix the problem. It ran fine for about 8 months. This just started happening again about 2 weeks ago. I unplugged the computer the other day and thought that fixed it but the problem came back the next day. I don't know what the problem could be. A scanner won't help because it's not showing any codes. When I put the jumper wire in place of the fuel pump relay, what am I bypassing? It seems that the problem lies in whatever it is that is being bypassed. Any help would be appreciated.

From what your saying ,you are bypassing the contacts of the relay and I would start looking at what controls the relay coil. good luck

Is there fuel at the rail?
Symptoms of a cold hard start is a bad, or dirty MAF sensor.

Do you have spark when this occurs?