We have changed the spark plugs,alternator and battery on our 2004 Chevy Trailblazer the gauges fluttered at first attempt at starting now it won't do any thing. What do I do???????????

Something in your computer controlled ignition system is shutting down. You need to check for trouble codes. Check for spark on a spark plug wire right after it stalls, or does it start right back up?

presure sensor evap

Sounds like you may have a bad valve cover gasket. same thing was happening on my wife's Chevy Aveo. Valve cover gasket was worn and when I replaced it and cleaned plug wells, issue was resolved.As for the breather, I really wouldn't know why there's water in there.Only thing I would suggest there is to check your antifreeze level. Is it water from the antifreeze?

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For engine to run it has to have:
Fuel, air and spark.
So if it doesn't start, something's missing.
Is your fuel pressure OK? Is your spark present? Is ECM firing injectors?
Check all those basics and I'm sure you'll find what's wrong.

could be a sensor...have it scanned...sounds like the problem....and good luck.

If it has not pulled any codes (idiot light). Clean your throttle body, and change your spark plugs with A/C Delcos #41-103, most other brands will cause rough idle like Autolites and Bosch. This would be a cheap way to fix this problem.

If by chance you have just recently changed the battery or had the battery unhooked. Let me know, it's an easier fix that costs virtually nothing.

You need to check the voltage at the battery itself, if the battery voltage is indicating in the area of 12.5 - 14.0 volts and your dash gauge does not agree, then the dash cluster has a bad stepper motor which drives the gauge.
If the battery voltage agrees with the dash gauge, and the alternator was changed and is assumed good, you need to check the wires going to the alternator, there may a broken connection.

CHANGING SPARK PLUGS IN TRAIL BLAZER. YOU NEED TO REMOVE AIR INTAKE RESONATOR AND IGNITION COILS.YOU NEED LONG 3/8 EXTENSION - SPARK PLUG SOCKET - 3/8 RATCHET WRENCH. NEED SPARK PLUG GAUGE AND A TORQUE WRENCH.YOU CAN GET BY WITH OUT ONE LONG AS YOU DONT OVER TIGHTEN PLUGS AND STRIP OUT ALUMINUM THREADS.

If you can't get the key out of the ignition, it's probably the ignition switch (where the key goes in) that is bad, not the starter. The starter is on the right side under the exhaust manifold behind the right front wheel. It's not easy to change on those unless you know what you're doing.

Not to worry this happens to everyone.

Many people seem to over look and understand that the battery is the mastmind behind this no start condition.

I would suggest that if you hear a clicking noise while cranking ( attempting to start) the engine; that you have a certifided tech inspect the charge of the battery.
This could also be , if it becomes something major, a no fuel condition. Meaning; your engine is not recieving fuel to combust.
Or a no spark condition which means that your spark plugs are not igniting your fuel.

But not to worry the problem could be your battery.