How do you test a fuel pump still in vehicle 0n 1989 Isuzu trooper 2 4 cylinder?

1. Check the fuel pressure. This can be done by connecting a fuel pressure gauge to the fuel line. The pressure should be within the specifications for your vehicle. If the pressure is too low, the fuel pump may not be working properly.

2. Check the fuel flow. This can be done by disconnecting the fuel line from the fuel injector rail and turning the ignition key to the "ON" position. Fuel should flow out of the line. If it does not, the fuel pump may not be working properly.

3. Listen for the fuel pump. The fuel pump should make a humming noise when it is running. If you do not hear the fuel pump running, it may not be working properly.

4. Check the fuel filter. A clogged fuel filter can restrict fuel flow and cause the fuel pump to work harder. Check the fuel filter and replace it if it is clogged.

If you suspect that the fuel pump is not working properly, you can have it tested by a qualified mechanic.