fuel problem

I have a 2000 chevy express 1 ton van, 454 automatic. Most of the time, but not all, you have to crank the key for 15-20 secs before she starts. The fuel pump went out, so I replaced it, hoping that was the problem. No luck... Lately, it is getting worse, and causing a strain on the battery.....does it whens it's hot or cold, sometimes it fires right up when its cold or hot.... nothing consistent...was told there was a 2 second relay, but caanot find it on the van, looks the same as the fuel pump relay, which I also replaced....Any ideas out there ????

The 2 second prime up is triggered by the VCM/PCM.
It uses the fuel pump relay. only one relay.

On the hard to start cold check fuel pump pressure.
Check cold start and engine running cold and the engine running on the road hot.
Specs are 55/62 lbs of fuel pressure.
Then check full pressure with return line pinched off.
Post back all fuel pump pressure readings.
It takes 60-61 lbs to squirt injectors on a cold start.
On a cold start key on it should prime up to 60-61 lbs and have 60-61 lbs engine cranking.

What brand of fuel pump did you install.

If a after market or Airtex pitch it and get a OEM delphi fuel pump.