Trouble starting a 99 suburban

I have been having some issues with my suburban lately. It has been in and out of the shop for various reasons. The last time it went it it needed a timing adjustment. It was really off. It ran great for a couple of days, but today it would not turn over. It started earlier (a little sluggishly) and I drove a mile to get to my daughter’s school. When I went to head home it cranked but would not turn over (it sat for about 1 hr). The radio came on and I kept trying and it eventually started. This was about 5-10 minutes of trying and checking the battery connections. I did pump the gas pedal a couple of times just before it started. My husband just did a tune up on it. It does occasionally start sluggishly–sometimes when it has been sitting for a while and sometimes when it was driven earlier in the day. This is the first time it has taken more than a couple of extra seconds to start. I had figured the starting trouble had to do with the need for a tune up and adjustment, but that does not seem to be the case. My husband has the habit of throwing parts at it until the problem goes away. This is getting expensive.

It’s apparent, from what some people say who come here for advice, that some people are change-parts addicts. No amount of advice seems to get through to them to try a troubleshooting approach. The question still comes, “What PART do I change for so and so problem?!” These people, apparently, don’t watch Dr. HOUSE on Fox TV. If they did, they would want to test and evaluate before coming to a diagnostic conclusion.
Spark and fuel control action need to be checked. There are small inductive lamps which clamp onto the spark plug wires to check spark to the plugs.
A fuel pressure test gauge is very useful to check static fuel pressure, AND fuel pressure when the engine is under load. Then, the engine is shut off, and the fuel pressure is observed for several minutes.
I know! I know! “But, what PARTS do I need to change?!”