If i put a little gas in the carberator and fight with my blazer it will start and stay started, but if i leave it for awhile, it will turn over but not start. i cant figure out if it is electric or mechanical but wondering how to test the fuel pressure regulator

Get a fuel pressure gauge and connect it to the rail for the fuel injectors to read pressure.

If the pressure is too low, it might be a bad fuel pressure regulator or pump:

Fuel Pressure Regulator Removal & Installation 2.2L Engine To Remove:

1. Relieve the pressure in the fuel system.
2. Disconnect the negative battery cable.
3. Disconnect the vacuum hose from the fuel pressure regulator.
4. Remove the pressure regulator mounting screw.
5. Remove the fuel pressure regulator assembly with O-ring. Inspect filter screen for contamination. If contaminated, remove and discard.

1. Apply clean engine oil to the new pressure regulator O-ring and install the O-ring on the regulator.
2. Install the regulator on the fuel rail. Apply thread-locker to the mounting screw.
   • Tighten the screw to 106 lb in (12Nm).
3. Connect the negative battery cable.
4. Use the following procedure to pressurize the fuel system and check for leaks;
5. Turn the ignition ON for 2 seconds.
6. Turn the ignition OFF for 10 seconds.
7. Turn the ignition switch back ON to run the fuel pump again and pressurize the fuel system.
8. Check the fuel rail assembly for fuel leaks.

1. Before servicing the vehicle, refer to the Cautions and Warnings in the beginning of this section
2. Remove or disconnect the following:
   • Upper intake manifold (See: Upper Intake Manifold)
   • Fuel pressure regulator retainer clip (M) and discard the clip
   • Regulator (N) from the housing by twisting and pulling the fuel pressure regulator (N) and using a shop towel to catch any spilled fuel
   • Regulator seal O-ring (R) and discard the O-ring seal
   • Regulator filter (Q) and discard the filter
   • Regulator seal O-ring (P) and discard the O-ring seal
   • Backup ring (O) and discard the ring
3. Cover the fuel pressure regulator housing to prevent contamination from entering the fuel system

1. Lubricate the NEW O-ring seals with clean engine oil
2. Assemble the following new parts to the fuel pressure regulator:
   • Backup ring (O)
   • Regulator seal O-ring (P)
   • Regulator filter (Q)
   • Regulator seal O-ring (R)
3. Install or connect the following:
   • Fuel pressure regulator with the vacuum tube pointing down
   • Fuel pressure regulator retainer clip (M)
   • Upper manifold
4. Test drive the vehicle to confirm the repairs

1. Before servicing the vehicle, refer to the Cautions and Warnings in the beginning of this section
2. Remove or disconnect the following:
   • Upper intake manifold
   • Fuel pressure regulator retainer clip (E)
   • Regulator (F) from the housing by twisting and pulling the fuel pressure regulator (F) while using a shop towel to catch any spilled fuel
   • Regulator seal O-ring (J) and discard the O-ring seal
   • Regulator filter (I) and discard the filter
   • Regulator seal O-ring (H) and discard the seal
   • Backup ring (G) and discard the backup ring
3. Cover the fuel pressure regulator housing to prevent contamination from entering the fuel system

1. Lubricate the NEW O-ring seals with clean engine oil.
2. Assemble the following new parts to the fuel pressure regulator:
   • Backup ring (G)
   • Regulator seal O-ring (H)
   • Regulator filter (I)
   • Regulator seal O-ring (J)
3. Install or connect the following:
   • Fuel pressure regulator (F) with the vacuum tube pointing down
   • Fuel pressure regulator retainer clip (E)
   • Test drive the vehicle to confirm the repairs