My 1997 monte carlo starts up fine and then shuts off do u know what that could be

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Hi,
Check the entire fuel delivery system.

• Relieve system pressure. Disconnect the negative battery cable and loosen the gas cap to let pressure drain from the system. Attach a dual tube pressure gauge to the test port and drain fuel into an approved container.
  
• Disconnect the fuel pressure sensor vacuum hose. Check for fuel in the line. If there is fuel present in the line, the fuel delivery problem is likely caused by a faulty fuel pump pressure regulator. If there is no fuel in the line, reattach the vacuum hose and continue with the fuel delivery diagnostic.
  
• Twist off the fuel pressure test port cap and attach a pressure gauge to the fuel pressure valve if one is not already connected. Reconnect the negative battery cable and turn the key to the first position. Do not start the engine.
  
• Check the pressure gauge. It needs to register between 45 and 48 psi. Start the engine and let it idle. Check the gauge again. It needs to register approximately 46 psi. Leave the engine on and remove the vacuum hose. Check the gauge one last time. It needs to register approximately 50 psi. Pressure that's too high indicates a malfunctioning pressure regulator. Low pressure indicates a clogged fuel filter or a broken fuel pump that needs to be replaced.
  
• Cut the engine off, relieve system pressure again and remove the negative battery cable.
  
• Clean the fuel filter inlet with compressed air to remove any dirt that might come loose and contaminate the fuel supply as you remove the fuel filter. Pull the filter out at the male filter fitting and disconnect the remaining connections to the filter. Remove the filter.
  
• Examine the filter for clogs and replace it if necessary. If there are no clogs, the fuel delivery problem is probably caused by a breakdown in the fuel pump itself.
  

DO NOT RUN OUT AND BUY ANYTHING YET! This was only the opening act.

All of the above systems are monitored by GM Powertrain Module (a.k.a. on-board computer). A diagnostic scan retrieves any inform related to the malfunctioning parts and tells you precisely what is wrong. Perform the scan diagnostic now.
Start the car and perform another scan. The reason we rescan and repair non-related codes after the engine is running is because sometime false codes can be triggered by the engine not running. Once the engine is running again the code present might cycle and turn itself off. You might say "if the engine doesn't run shouldn't it have a trouble code?" Sometimes conditions occur that will not be detected by the computer, e.g.,if the fuel pump fails the computer cannot detect the failure, so the engine doesn't start and the computer thinks everything is okay with no codes. If no trouble codes are present proceed to the next step.
If you have trouble using the code scanner or interpreting the codes click on the following link and use my access code (carrepair): Free Automotive Repair information for Users of a Code Scanner
I know that the above is wordy but I wanted to do more than just tell you that your problem is complex.
All the best,
Ben