My chevrolet tahoe wont start, no spark, fuel pump not working but will if directly connected to battery, but still wont start since no spark, allarm going crazy 2

If the battery is dying that quickly you need a new battery
On the Tahoe K series 5.7L the fuel pump relay is in the engine compartment to the rear of the engine control module, should be identified on the cover over the relays
https://fuse-box.info/chevrolet/chevrolet-tahoe-1995-1999-fuses-and-relay

https://scanneranswers.com/signs-of-a-bad-fuel-pump-relay/
https://easyautodiagnostics.com/gm/4.3L-5.0L-5.7L/testing-the-fuel-pump-relay-1

Hello. Yes, your Chevrolet's security system will 'shut-down' the ignition system; causing your truck to start but stop instantly. The truck 'thinks' it is being 'stolen' and will 'enable' it's security system to 'hamper' stealing it. Good luck and keep me informed; if you want to.

Are you missing anything else, besides gas? Engine cranking, did you check for spark at the plugs and fuel injector pulse? Any applicable trouble codes? Did you check voltage and ground to fuel pump motor, before replacing anything?

Sounds like a fuel delivery problem. Has the fuel filter ever been changed? You can try banging on the bottom of the fuel tank with a blunt object ( hammer works ) while some one cranks the engine. If it starts suspect a bad fuel pump

CKP sensor is located at front/lower of engine near crankshaft damper. Check for spark. Should blue with spark plug wire one half inch away from a good ground.

Well,first off you need to make sure you are getting spark to the spark plugs first.Get some insulated pliers and pull off a spark plug wire,hold it next to the frame or exhaust and have someone spin the engine over.You should see spark jumping between the plug and the ground.If you do not,then you have an ignition problem.If you can spray fuel in the intake and it wont even try to start,then it sounds like you have an igniton problem.Verify that before going too far with the fuel system.If you have spark,then it may be your ECM could be fried and is not letting the fuel injectors open but it should still try and start if you are spraying fuel directly into the air intake.IF it has spark.

Loose battery cable at the starter end, or sensor trouble, tighten cables, see if this helps, usually does, I get 50.00 per hour to check this, I render this 4 free 2 u.
Thnx 4 using fixya.com

check for spark and fuel at the motor! take one of the spark plug wires off and remove the spark plug and put the wire back on it and rest the spark plug on a negitive ground point and have someone try to start it and see if the is spark. to check to see if fuel is getting up there locate the fuel presure relief valve on the fuel rail that the injectors are connected to and while someone it trying to start it depress the valve and see if fuel squirt out.

Yes, it's more than likely your fuel pump.

Your Tahoe does have a vacuum line connection to the regulator. It's also possible the regulator itself is bad,
Greg