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Re: How much psi is coming from the fuel pump
38.0 - 44.0
30.0 - 37.0
Y251: Pressure (PSI) is measured at cold start injector with pressure regulator vacuum disconnected. Y252: Pressure (PSI) is measured at cold start injector with pressure regulator vacuum connected.
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Internal pressure regulator on the fuel pump should hold for about a minute but some pressure loss is normal. However, on initial start-up, the pressure must be at operating pressure or the system wont work. I suspect the fuel pump is failing, it is an all too common problem for GM trucks and SUVs with mpfi fuel injection.
IACs do not go out very often, usually there is a problem with vacuum leaks, dirty throttle assemblies.
sounds like it could be a cpule things, i would start with replaceing the fuel filter and re-testing if that yeilds no change unplug the fuel presure regulator or if posible temp clap off the return line and check presure again, if it comes up to where it needs to be then replace the regulator. finnaly if none of those things solve it i would be very suspect of your fuel pump modual. good luck! let me know if i can be of further help, please rate my answer take care
check the fuel presure reg but first check fuel ammount place fuel line un hooked in 1 galon glass jar turn ignition to run position container should fill quickly mesure fuel amount from single cycle call dealer ask what flow amount should be with single purge cycle
this will tell you if pump or filter are problem it will allow you to see if fuel filter is pooched and **** is bypassing also or if it is pluged
if results proper or close to dealer spec check fuel rail for bad fuel presure regualor if reg bad there will be little or no fuel presure even during purge cycle if flow high and finger cant hold presure if is usually fine and reg is bad pick up new reg from salvage it will cost 5 - 20 bucks and if a likely culprit
get a fuel presure gadge and check the presure after setting hook up the gadge starty it up let it set see if the presure drops to 0 if so and you have no fuel leaks and you know that none of the injectors are leaking then it might be the fuel pressure regolator or the fuel pump the psi should be around 35 40 psi i think