You can use the fuel pressure gauge in your car to determine what the problem is when your car isn't running properly. If you have never worked with a fuel pressure gauge before though, there are a few steps that you will want to follow:
Step 1 - Find the Port
Refer to your cars manual to locate the test port for the fuel pressure. For some cars you will need to get into the fuel supply line.
Step 2 - Start Car and Read
Once you hook it up, you can turn on your ignition. Take a reading right then to see what it is. Then start the car and let it run while you record another reading. Then, with the help of a partner, drive the car and take a reading from the pressure gauge to see what the pressure is.
Step 3 - Compare and Interpret Readings
Check your cars manual to see what the pressure readings should be. If you find that the reading comes out lower than it should be, replace the fuel filter first and then see how that affects it. Take another reading as you did in step 2 to make sure that the problem is remedied. If not you may need to replace fuel pump or pressure regulator.