With a fuel pressure gauge: 1) "This new B&M fuel pressure gauge allows you to accurately measure fuel pressure. Proper fuel pressure is critical at wide open throttle to prevent lean conditions. This is also a great tool for tuning your engine to produce maximum horsepower at all rpm ranges. It will work with all naturally aspirated and forced induction engines." http://www.jazzproparts.com/category_s/740.htm 2) "Snap-On Fuel Pressure Gauge Kit Part Number: MT337B What it is? Snap-On fuel pressure gauge kit able to work with most OEM vehicles. What can it do? It is specifically designed to measure fuel pressure in pounds per square inch. The kit includes many different adapters to work with most electronic fuel-injected cars. How does it work? A fuel pressure gauge and all the adapters needed to fit on most vehicles is provided with the kit. The gauge hooks up in parallel with the OEM fuel system, allowing you to monitor fuel pressure from idle to under full load. The gauge hose is very long to run outside of the engine bay when monitoring fuel pressure while driving. One of the best features is gauge's ability to purge the pressure build-up through its release valve; this allows you to bleed the pressure before removing the adapter. Cool Trick Most new vehicles have a Schrader valve attached to the fuel system; if you're lucky, your car has one of these to make checking the fuel pressure much easier. Find it at: www.snapon.com" 3) "Choosing the Right Pressure Sensors for Engine Test" "You measure fuel pressure during fuel pump and pressure regulator tests." http://www.sensotec.com/pressure_sensor_appnotes1.shtml 4) "An EFI fuel pressure gauge (highly recommended!!). A tire pressure gauge can also be used, but I DO NOT recommend using one! Just pushing in on the Schrader valve to see if there is pressure present is NOT sufficient!!!" http://www.turbotbird.com/techinfo/Fuel_Pump/Fuel_Pump_Diagnostics.htm

You measure fuel pressure with a fuel pressure guage- probably left for a neighborhood mechanic if asking though.