Guys, I'm looking for suggestions or answers. I have a 2010 2500 that's been deleted and running a Smarty Jr. It's been deleted for several years and it has 47K miles on it. Two weeks ago I get in it and drive down and fill the tank. No problems. Last weekend I get in it and it look longer than usual to start. It cranked for about ten seconds before it fired up when usually it only takes a couple of seconds. It did this all weekend. Today I got in it to see what it would do. The first time it cranked for 15 seconds or so without starting. I shut it off and tried it again and it took another 10 seconds before it started.
I replaced the fuel filter today. First time I tried it after the filter change it fired right up. Let it idle up to operation temp and tried it again and it fired right up. I let it sit all day and tried it again and I'm back to the long crank time. Any input will be appreciated.

 

I would do a fuel pressure test of the output of the in tank lift pump

 

I have no gauges to pressure test the pumps or fuel rail.

 

The fuel rail will have some really big dangerous pressure