I PUT A FUEL PUMP AND FUEL RAIL PRESSURE SENSOR IN AND STILL HAVE LOW FUEL PRESSURE WHAT COULD BE THE CAUSEé

cloged injectors or bad fuel pressure regulator.when you replaced the parts did you bleed the air out of the fuel system.

the regulator is on the new fuel pump assembly i put in, i did a terra clean to it too. put a new fuel filter and the module that controls the fuel pump in the rear of the truck i changed to. i looked on Mitchell and it says the mass air flow sensor can do it to,

OK but did you blead the air out of the system,on fuel rail you will see a valve,looks like a metal tire valve,remove the cap,turn key switch on,dont start engine,use a small screwdriver or something pointed get a rag push down on the pin in valve to release any air,do this 2 or 3 times until gas sprays out,keep rag over valve at all time to elemate gas spray.A bad MAF would not cause low fuel pressure,unhook the hose in front of MAF,see if it is black on the screen if not it is ok.