2000 malibu starts & then shuts off

Take it to a mechanic

Spray ether in the intake and turn over if it starts and runs while spraying and then dies when you stop spraying....its the fuel pressure regulator or the fuel pump. Watch out for back fire #hoonigan

Check to see if the fuel pump is actually receiving power and pumping the gas to fuel rail or carb.

This is fairly normal for cars left standing for lengthy periods, u can start most vehicles by spraying fuel directly into carb, or a great product called Bradex in the air intake, this is an ether in a can, once the engine starts it should run, but some vehicles that r started this way to often, get to start only this way, it sounds like despite new pump, the fuel is draining back over night & not there for starting in the morning, check ur fuel lines I bet its 1 of them causing the drain back, fit a 1 way valve as close to the carb/injector system as possible

Pull spark plugs. They are water /gas soaked Dry them up and retry. Spray some Quick start. I.e. ether. in intake duct then start

Your fuel pump isnt working, you can check this by taking the fuel cap of and turn the key to the start position have someone listen closely by the gas fill port you should here a humm or wine if you dont the fuel pump is bad and needs replaced

Here is a pic of a schrader valve. They all look about the same.
If there isn't much pressure, cycle the ignition without turning the engine over and try again. If it is still weak, you may need a new fuel filter. If it is strong, you may have dirty or clogged fuel injectors.

It may be spark, but I'm inclined to think it is fuel related.

Good luck, and keep us in the loop!
JT

check the fuel pressure in the rails. There may be a low pressure that will not allow the spray to be misted enough. It could be a clogged fuel filter also.

Fuel pump, you have to have press in the rail to fire all injectors- she will run on ether but not good for her. Ck your pump and any related fuses,relays,wiring.

Check the fuel pressure at the Shredder Valve, You should have 60PSI to 65PSI upon start and should drop about 5PSI when running. If your fuel pressure is good then it may be a bad injector system. The fuel injector spider system that the vortec has are know to go bad, from the fuel pressure regulator to the puppet fuel valves. Change the fuel filter first if it has not been changed yet and have the fuel pressure check. Good luck and keep me posed. Note: it's been know that spraying ether to start the vortec with the spider injector system has got the puppet valves to catch fire and melt the ends of the puppet valve leading to the replacement to the whole system. Good luck and keep me posted, be glad to help.