My engine is hard starting?

55 psi is weak for these trucks. 60-66 is what it is supposed to be with the key on and engine off. It should bleed down losing maybe 1 or 2 psi per minute to start. And they really do need 60 psi to start like they should.

Hmmmmmmmm. This may seem like it's coming from left field but have you had the battery tested? Could be delivering weakish sparks when cranking.

If the new fuel pump is an aftermarket pump, then that is what the problem is. Once warmed up, it cannot quite put out the fuel pressure that it is supposed to. Hence the long crank time. My 2002 does the exact same thing and has an aftermarket pump in it. The problem started when I put that pump in.

To confirm, try priming the fuel system by turning the key on for five seconds, then off. Then repeat that twice more (total three times) and then crank it. It should fire up much easier.

Have you run a fuel pressure test on it? I would start there. Simply borrow the gauge from AutoZone or whoever has a loan-a-tool program near you. Warm the truck up. Then shut it off and wait a while. The hook up the gauge, turn the key on, and see what it reads. This truck needs 60psi to start. Any less will cause issues.

Here is a general how to guide: https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

Scan for codes and check for a vacuum leak then compression. Also, check distributor rotor to see if it moves if it does the distributor gear is probably shot.

Hi:
When you have the no start problem, have you checked for both fuel and spark? If you have both, you may need to check the engine's compression. Let me know so I can further advise you.

Joe

Have you checked to see if the spark is a hot blue snapping spark?

One other thought is the temp sensor. It's purpose is to tell the computer the ambient temp and the coolant temp. If it isn't recognizing the correct temps, the engine will be hard to start. It basically took the place of the choke on a carb. You may want to recommend having that checked too.

Sounds like the fuel is draining back out of the system. The common reason for that is the check valve in the pump failing and the fuel drains back.
To see if this is the issue try a simple test. Turn the key to "on" then "off" two to three times to run the pump prime and fill the system. If it starts okay after that you are losing the fuel pressure when it sets still. Easy to verify if you put a pressure gauge on the system. When you turn the key on the pressure should go up to 55-60 psi, turn the key off and it should hold there, If it drops off the check valve is leaking.
Then you just need to determine if it's leaking back into the tank or if the injection is leaking internally. Easy way to tell if that is the case. Has the gas mileage dropped a lot when this started? If yes it is likely an internal leak, no means it is the check valve in the pump.

If it is the check valve you have a couple options, drop the tank and replace the pump assembly (use a GM/Delco/Delphi pump) or you can add in a check valve in the fuel line to hold the pressure.