GM Truck Club
THE PREMIER CHEVY TRUCK & SUV FORUM
Founded in 2004 ~ We're the #1 Chevy Truck & SUV Forum.
Silverado & Sierra | Tahoe & Yukon | Suburban & Yukon XL | SUV & CROSSOVER
Results 1 to 5 of 5
  1. #1
    Jr. Apprentice
    Join Date
    Mar 2010
    Location
    Maryville, TN
    Posts
    18

    Default 99 5.7 Vortec - what is fuel pressure spec after MFI upgrade

    I changed the fuel injector assembly from the stock CSFI to MFI about 30k miles ago. Now when I check fuel pressure, I read 55 lbs. Does anyone know what the correct spec for fuel pressure should be after you do the MFI upgrade on a 99my 5.7L Vortec?

    I am trying to track down a problem I believe to be engine related. It seems to buck & surge while I drive, almost like uneven cylinder firing.

    99MY K1500 Suburban, 5.7L, 200k miles.

  2. #2
    Jr. Apprentice
    Join Date
    Mar 2010
    Location
    Maryville, TN
    Posts
    18

    Default I checked the mechanical timing again

    After replacing the distributor and not finding any difference in the way the truck runs, I took it apart to double check the timing. Everything lines up - at #1 TDC ( I tested by taking out the plug & feeling compression ) I had the distributor lines up to the correct mark, just like it shows in the factory service manual. Do I need a scan tool to check the timing?

    I have had the battery disconnected. Does this cause the Engine PCM to forget any learned timing offset?

    Still haven't found the fuel pressure spec for MFI. Next I will change the fuel filter because it is due again anyway.

  3. #3

    Default

    hey there, I am having the same problem after replacing my scfi to mfi. Was wondering how or if you resolved your problem. I smell half burned gas as well and getting poor fuel consumption.
    thanks in advance

  4. #4
    Sr. Engineer
    Join Date
    Oct 2010
    Location
    Indianapolis, In
    Posts
    493

    Default

    The fuel pressure for the 99 to 2006 V8 is 55 to 62psi for reg gas engine. this is for Sequential Fuel Injection SFI. What upgrade is available?
    2000 GMC YUKON SLT, 5.3L tow pkg, G80 rear/w 3.73 gear

  5. #5

    Default

    Quote Originally Posted by triple-4x4 View Post
    I changed the fuel injector assembly from the stock CSFI to MFI about 30k miles ago. Now when I check fuel pressure, I read 55 lbs. Does anyone know what the correct spec for fuel pressure should be after you do the MFI upgrade on a 99my 5.7L Vortec?



    .
    The MPFI manifold needs the same 55-62 psi as the SFI, and yes, you need the proper scan tool to view and adjust timing on 96-2002 Vortec 5.7s.

    97 Chevrolet Suburban K1500 5.7L
    78 GMC High Sierra K1500
    Fat, drunk, and stupid is no way to go thru life.

Similar Threads

  1. fuel injection parts off 97 5.7 350 vortec
    By laoutlaw in forum General Classifieds
    Replies: 1
    Last: 06-05-2010, 02:19 PM
  2. 5.3 fuel pressure?
    By slider_buck in forum Performance & Fuel
    Replies: 2
    Last: 04-08-2010, 05:25 PM
  3. What is your oil pressure? 1999 Suburban Vortec 5.7
    By jn1965 in forum GM Diesel & DuraMax
    Replies: 14
    Last: 07-22-2009, 05:24 PM
  4. 5.7L Vortec Oil Pressure Sending Unit
    By Howie in forum GM Powertrain
    Replies: 5
    Last: 01-25-2009, 09:58 AM
  5. No fuel with no oil pressure
    By 70boss302 in forum General Chevy & GM Tech Questions
    Replies: 2
    Last: 08-22-2008, 11:28 PM

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •