GMC Repair: 98 GMC will not start, starter fluid, adivce

Question
I have a 98 GMC 5.7 that will not start. This is the third time this has happened. the first two times were in the morning and after a few days it started with no problem and ran fine and started every time for a few days. this last time it has been about a week and I try about every day and nothing. I have checked and have spark at the plugs, I've checked for corrosion at the dist. cap, none, and I've tried starter fluid and gas in the intake and nothing. It does seem to backfire when I tried to start it, it has done that every time it has not started. The check engine light has not come on. Any help would be appreciated.

Answer
Hi
First starting fuid is not a good idea. It can explode and cause catostrophic damage.
I would get the fuel pressure checked. (60-66psi)
If you have spark, fuel and compression, thats all you need.
My best adivce, is to take it somewheres and have it professionally diagnosed. If it is backfiring it is not getting either proper spark, or it is not sparking at the correct time.
I Hope this helps
Pawl