Maintaining the proper pressure in your fuel system is the key job of your Chrysler fuel pump. The fuel pump is activated for only a few seconds at a time. As soon as you turn the key in the ignition, the pump pressurizes the fuel and must keep the entire fuel system to a specific pressure level. When the engine cranks and an oil pressure switch in the engine closes, the fuel pump shuts off. Pressure is vital for maintaining the steady flow of fuel that fuel-injection systems require. The new Chrysler fuel pumps ensure a steady pressure throughout the entire fuel system. Be aware that there is a "rest pressure" in the fuel system that can be measured when the engine is off. Too-high pressure can cause the fuel pump to work too hard and fail prematurely; it can be caused by a faulty regulator or crimped fuel return line. Poor "rest pressure" can be caused by a leaking regulator or fuel injector. Low pressure can cause hesitation, a rough idle or lean misfires, which indicates that the fuel and oxygen levels are not sufficient to sustain combustion. If you want to check the pressure regulator, crimp the return fuel line that leads to the fuel tank. You should see a quick boost in the fuel pressure if the regulator is failing in your Chrysler fuel pump. Likewise, you can test every section of the fuel system's pressure by cutting off the fuel flow and measuring the results.