The key has 4 positions: OFF, ACC, ON, and (spring loaded) START. You can turn the key to the ON (run) position but do not continue past that to START. When the Key is first turned to ON the fuel pump runs for 3 seconds to pressurize the fuel system.
Your Fuel Pressure Regulator is in the fuel rail on the rear right end - a dome-top small metal can held in the fuel rail by a hairpin clip. On the top is a vacuum connector which comes from the throttlebody casting. Remove the vacuum connector from the FPR nipple and have an assistant turn the key ON while you watch the FPR. Does any fuel come out of the FPR metal nipple ?? Now START the engine while plugging the vacuum line with your finger and watch the FPR nipple. Does fuel weep or spray out ??
If the FPR leaks, replace it.
www.rockauto.com. "fuel/air", "fuel injection pressure regulator". Smear a drop of engine oil on the O-rings and make sure the small bottom O-ring slides down into the fuel rail fitting.
Another cause of low fuel mileage is a dirty air filter. Check yours and if you can't see light through it when you hold it up to the sun, replace the filter. Careful: do not damage the MAF (Mass Airflow Sensor).
You
need a GM/Helm Factory Service Manual - either from eBay or
www.helminc.com or subscribe your car to
www.alldatadiy.com
