Jump to content

Fuel Pressure Values Please

DSN46

Recommended Posts

DSN46 Enthusiast

DSN46

Posted
Posted

Hello,

 

I have a 04 Suburban 1500 Vin code "Z" Flex Fuel. I have recently had idle problems along with "almost stalling / low rpm" problems when at a stop. I have a cheap sears fuel pressure tester (may not be most accurate) and have tested the pressures at the Schraeder valve as follows:

 

KOEO= jumps to 52 at first then drops to 46 immediately.

After 10 min = still holds at 46 psi.

After 30 min = still at 46 psi.

 

Engine running at Idle = 42.

1000 through 3000 rpm it holds at 42 to 41 psi.

When I stomp the accellerator, it jumps to 52 then drops back to 42 again quickly.

 

Could someone please look at my numbers and tell me if they think I have a fuel pump problem or maybe FPR problem? (no gas leaking at FPR by the way) Are these numbers okay for a flex fuel engine? I know the flex fuel should be a little lower than the regular engines. If these numbers are okay, then where would you look next for possible causes of low idle rpms? Oh yeah, it does it whether AC is on or not, but MORE so with AC on.

 

EDIT: I forgot to mention that I have removed the throttle body and cleaned it thoroughly as well as cleaned the MAF sensor and replaced the MAP sensor. Also, Intake Manifold Gasket replaced by dealer.

 

Thank you all very much!!

 

James

txab Senior Enthusiast

txab

Posted
Posted

For a T code engine KOEO value is 55-62. I would think your engine would be similar. You could change the FPR. If problem still exists change the pump. That's where I'm betting your problem is

DSN46 Enthusiast

DSN46

Posted
  • Author
Posted
For a T code engine KOEO value is 55-62. I would think your engine would be similar. You could change the FPR. If problem still exists change the pump. That's where I'm betting your problem is

 

Thank you for your fast response! I knew the pressures for a VIN code T engine, but I read somewhere on another forum that the Z code engines had less pressure in them.... however, I cannot seem to find exactly what that pressure is, or if my "immediate Key-On of 52 then drop to 46 and hold" with engine off is acceptable or not. Hoping someone with experience with the Z coded engines will know exactly.

 

Thank you again!

 

James

txab Senior Enthusiast

txab

Posted
Posted

Have found conflicting info on fuel pressure readings for a Z. I'm sure 46 is too low. What about the fuel filter? IIRC '04 "Z" code still has an external serviceable filter on the rail. Might check it for sure

DSN46 Enthusiast

DSN46

Posted
  • Author
Posted
Have found conflicting info on fuel pressure readings for a Z. I'm sure 46 is too low. What about the fuel filter? IIRC '04 "Z" code still has an external serviceable filter on the rail. Might check it for sure

 

 

Thank you again! I agree with you that 46 is too low. What I am not sure of, is if it is the Fuel Pump... or the Pressure Regulator like you mentioned before. Since it starts at 52 - 54 psi. right when key is turned on, then about one second later, it drops to the 46... it leads me to believe that the pump is doing it's job, but the regulator may be hindering things. I am going to replace the regulator tomorrow and see if any change occurres. Also, I considered the filter also, but I just changed it about 15,000 miles ago, I cant see it being the problem yet.

 

I appreciate your help on this as I dont want to just keep throwing parts at... something I think alot of us are guilty of, unless you happen to own your own, personal Tech II Programmer.

James

Archived

This topic is now archived and is closed to further replies.

Go to topic listing

  • Recently Browsing   0 members

    • No registered users viewing this page.

  • Forum Statistics

    250.6k
    Total Topics
    2.7m
    Total Posts

  • Member Statistics

    343,007
    Total Members
    8,960
    Most Online
    Brendan C
    Newest Member
    Brendan C
    Joined

  • Who's Online   4 Members, 0 Anonymous, 992 Guests (See full list)

  • Latest Articles

  • Posts

    • richard wysong
      Electrical Problem - solved

      By richard wysong · Posted

      Thanks for posting, I'm sure it will help someone
    • Brendan C
      2026 6.6 L5P oil cooler leaking oil at 4,000 miles

      By Brendan C · Posted

      New to diesel trucks. I happened to find my oil cooler leaking oil externally with only 4,000 miles on the truck. I didn’t realize this was an issue until I started researching it. Dealer is going to replace it under warranty but I’m wondering if there’s anything GM is working on to fix this issue. I’ve heard the oil filter used is the same as they use on their V6 motors and that’s what is causing the problems. Should I switch to a bigger filter or keep using the OEM recommended? 
    • Vu1can
      Seems to be Missing a lot of Updates

      By Vu1can · Posted

      So, GMCustomerService:  Judging by the Update History pictured above, is this truck missing any updates that it actually needs. If it's just for the infotainment system, the radio is working fine and no trouble with SeriusXM. and Android Auto is working fine wirelessly with my phone. Some months ago, an update notice was sent to my truck. I approved the update and it finished saying that the update was successful, but it seems that whatever that update was, it didn't actually get installed - at least not if I'm to go by the Update History shown above.   So, again, are there any updates that this truck really should have? I've checked with my dealer but they're reluctant or commit to anything and if I want them to check, they require a $200.00 fee just to check it out and then I'd have to pay for the actual update(s).    Ignorance is bliss, and if none of the updates goes to fixing any mechanical discrepancies, I'll just leave things as is.  
    • CNH-320
      Electrical Problem - solved

      By CNH-320 · Posted

      Hey everyone, I recently had an issue with my 07 2500HD GMT900. My DRL’s stay on at all times. Right front turn and right mirror turn signal indicator stay on solid at all times. By “at all times” I mean the only way to make them go off is disconnecting the battery. I tore the headlight assemblies out, tried disconnecting the harnesses to eliminate bad wiring at the harness, I unplugged the headlight switch, no change and the mirror turn signal still stayed on. My first thoughts were : Bad bulb and/or socket somewhere, under hood fuse panel bad, bcm bad, tail light or trailer wiring problem, or some random short to power in the harness.  Possibly a bad ground but unlikely. I had a big clue in the fuse panel, it had a burnt smell. I started pulling every fuse that had to do with DRL or right turn/park lamp. Nothing made the right directional turn off but pulling the DRL2 fuse made the DRL’s go out.  After studying wiring diagrams, I found that both problems had that fuse panel in common, the bcm also controls both problems but knowing the fuse panel had a burnt smell I removed and disassembled the fuse panel and found a little corrosion on the printed circuit board.  I ordered a new fuse panel from Amazon for like $260. When it arrived I installed it, and put everything back together, the problem was fixed. I figured the fuse panel needed to be replaced anyway so that was a logical place to start. Hopefully this story helps someone in the future. Regretfully I didn’t scan for codes before I did everything.
    • 2022LtTbZ71
      Service 4wd, ESC light, traction control light on, Service charging system (vehicle may stall)

      By 2022LtTbZ71 · Posted

      That stinks. I’m sitting on the side of the road right now with the same issue. Never had an issue before taking it in for the ground strap recall. Now I’m outside of warranty and they’ll probably want $200 just to diagnose what they already “fixed”. 

  • GM-Trucks.com Clubs

  • Popular Contributors

×
×
  • Create New...