My truck is hard to start?

Either not enough fuel pressure or a clogged catalytic converter. You can borrow a fuel pressure tester from the local parts shop and hook it up to the test port. Turn the key on, and you should get a reading of 55-62 psi. With the engine idling, you will see a drop, which is not laid out by GM. But I would think it should still stay above 45 psi. If it drops as the engine warms up, then you have found your problem.

this guide can help us fix it

https://www.2carpros.com/articles/engine-cranks-excessively-before-starting

The test for the catalytic converter is a little simpler. The problem with a clogged converter is that the exhaust cannot get through fast enough, so it creates back pressure on the engine, keeping it from breathing and causing it to bog down and generally runs bad. The test is to simply take the upstream oxygen sensors out and go for a ride. Yes, it will be "make the neighbors mad" loud, so do it in the middle of the day. If the truck runs noticeably better, then your problem is the catalytic converter.

Does that make sense to you? Let us know what you find.

Try checking the fuel regulator or fuel pump. Sounds like the regulator is leaking fuel into the system. Then when you try to start it, it cranks over several times to expell the excess fuel. Test with a fuel press gauge.

Chances are the fuel pump is pumping fine, but loosing its prime when the key is off. The schrader valve is on the fuel rail to check pressure. Here is a how to for checking pressure. WHen you check it, pay special attention to fuel pressure drop off. THat is when you shut the key and the pump is off. Does the system maintain pressure???

https://www.2carpros.com/how_to/how_to_check_fuel_pressure.htm

Let me know what you find.
Joe

Really there are no other questions. If the pressure is low, that will cause the problem. Unless, there is a leak in the system. Did they tell you that it was loosing its prime (fuel pressure drop off)?

You need to check fuel pump pressure, the regulator, and fuel pressure drop off. Drop off is when the key is turned off. The system should maintain pressure. If it doesn't, you lose the prime and it will take a few tries to start it. Here is a how to for checking all that I mentioned. You will need a fuel pressure gauge. Most parts stores will lend them to you.

https://www.2carpros.com/how_to/how_to_check_fuel_pressure.htm

Let me know what you find or if you have other questions.

Joe

Using a fuel pressure gage, how fast does the pressure bleed off, everything turned off? Maybe the fuel pressure is bleeding into the engine?

If pressure holds that long, sounds good. Did you take the throttle-body off and clean it?

Something common to all your cylinders, fuel or air, egr? You may need to use a scanner that will show live engine data. You can use a dmm to look at some sensor signals, engine running. If you suspect a sensor. At idle the map and tps usually show close to the same signal voltage, may not exact to the tenth of a volt, but close.