2004 4.3L Chevy fuel noise

Bad regulator, leaky injectors, leak in lines somewhere. Since it runs ok once started, I suspect leaky injectors.

Yes the thermostat so stuck open not allowing the motor to properly warm up or it can be the climate control went bad

Sounds like the fuel pump is going bad(or in this case,has gone bad). I suggest that you change the fuel pump and use a fuel cleaner in your gas tank as dirty gas may have caused the problem to begin with.

i'd agree sounds like a faulty oil pressure switch.doing a pressure test with a guage will
tell for sure or just replace switch ($15 part)

good luck

could be map sensor, could be fuel filter,if it was a sensor your check engine light should be on. i have a 2002 chevy avalanche and it was hard to start and the fuel pump was working but it has a valve in it that will not allow the fuel to run back into the tank and empty the lines, and the valve was bad which the only way to fix the problem was a new fuel pump unfortantually just cause it is a new fuel pump does not mean the check valve in it did not go bad

did you install the oil pressure switch origional to the tahoe? The tahoe uses a low oil pressure shutdown, instead of an inertia switch to shut off the fuel pump in the event of an accident. If the pressure circuit does not close within 3 seconds after the engine starts the fuel pump shuts off. This is in case the truck is on its side or upside down the pump will shut off.

will not start or will not turn over?

If it ran out of gas you'll need to purge the air out of the fuel line. Chances are also good that you pulled some sediment off the tank bottom and clogged the filter. If that's the case you'll need to replace the filter.

If you haven't had any luck yet, I suggest that you #1 replace any rubber fuel lines that are obviously bad or even questionable. CJ's had mechanical fuel pumps mounted on the side of the crank case which ran off the cam. This means that there is no pump in the tank and any fuel lines leading to that pump will be under a vacuum. If those rubber lines are wrong kind, old or almost kinked they WILL colapse under the vacuum and temporarily shut the fuel off. #2 However, in your case it sounds like the little screen filter on the pull tube inside the tank is probably stopped up completely with debre, that's why the motor dies and won't start again. If you drop the tank and remove the screen sock from the end of the metal tube that may solve one problem. If you do this though, I suggest that you put an inline filter somewhere before the pump.

take off the fuel line at filter and see if gas comes through. If it is elsectric it should make a noise not real loud but a noise.