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  1. #1

    Default stumped after engine swap ~ 5.3 to 4.8 in 2006 Z71

    I changed out my 5.3 to a 4.8 in my 2006 z71 it will turn over but will not fire have already changed out coil packs any suggestions would be appreciated

  2. #2

    Default

    We might need more info on this one. Did you change the ecm? did you have it reprogrammed? How is the fuel pressure?

    1995 Silverado 4x4
    6" BDS Suspension Lift-3" Body Lift-Add A Leaf in rear -Trailmaster SSV Shocks-Duel Steering Stabilizer Kit -AirAid Cold air intake-
    4.56 Gears with Detroit Auburn Locker-Pro-Comp Traction Bars with duel shocks-Aluminum Skid Plate Kit-38.5" x 16.5" Mickey Thompson Baja Claws-Constant Dropping fuel gauge

    2005 Yukon XL Jet Power Programmer, Bilstein Shocks, Bilstein rear springs, Helwig Anti-sway bars, EGR Window Visors, EGR Hood Shield, Denali Headlights, Headlight harness upgrade, GE NightHawk Bulbs, White Night Rear lighting system, Russell Braided SS brake lines, PowerStop Brake pads, PowerStop cross drilled and Slotted Rotors, http://www.gmtruckclub.com/forum/sho...5-GMC-Yukon-XL
    2002 Silverado ext cab 2wd (Sold)
    2003 Yukon XL (Totaled)

  3. #3

    Default

    Has got good fuel pressure. No didn't know I had to change the ecm also think security system may have faulted out because when I turned the key over lights went to flashing and horn honking

  4. #4

    Default

    Hopefully someone else can help here. I am pretty sure that the ECM control timing, fuel delivery, and a bunch of other things. I am going to move this thread into the power train sub forum to get you better results

  5. #5

  6. #6

    Default

    Quote Originally Posted by sheldon70 View Post
    Has got good fuel pressure. No didn't know I had to change the ecm also think security system may have faulted out because when I turned the key over lights went to flashing and horn honking
    I understand that you are looking for assistance in resolving your vehicle issue yourself and I might not be able to give you any technical advice. If you find that you cannot resolve this vehicle concern yourself, I am happy to assist with any general questions or concerns you may have.

    Regards,

    Jennifer T.
    GM Customer Care

  7. #7
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    Default

    Quote Originally Posted by sheldon70 View Post
    I changed out my 5.3 to a 4.8 in my 2006 z71 it will turn over but will not fire have already changed out coil packs any suggestions would be appreciated
    with the security light on the vehicle will not start. now I do not understand why an engine swap would cause the security to be activated.

    since the engine is cranking then I would measure the fuel pressure. engine swaps could mean many things . give details about the replacement engine . what you did to do with this swap ? engine come with manifolds intake exhaust/throttle body/same year or what year ? injectors /coils with engine or swapped stupid stuff like this .....

  8. #8

    Default

    @sheldon70 has the engine ever run in the truck?
    Ray

    '09 Avalanche LTZ - Black
    '05 Envoy XL (sold)

  9. #9

    Default

    make sure your getting spark and fuel first off. and id look intom a pcm or a tune.... also what did u do a 5.3 to a 4.8???
    2004 gmc sierra ext z71 5.3
    PERFORMANCE...
    KB racing hot pipes 3.5" : 76mm turbo: 4l80e : Circle-d 2b multi disk :Walbro 400 : Racetronix Hotwire kit : TB coolant bypass : Nelson 91 Pcm : Tr 220 Cam : Brian Tooley double springs kit : Ls7 Lifters : Stage 3 heads : Custom Intake Manifold :80lb Injectors : Ported TB : 40k tranny cooler: Plx dm-100 gauge: Auto meter fuel and boost gauge:
    APPEARANCE...
    Custom Speedo : Leveling kit :Smoked led taillights and 3rd break light : Black projectors and fogs with hids : Blacked out grille : 33's on 16's : Clarion flip screen: sound que 12" subs: clerion 6x9's : Memhpis amps: Alpine componet set.
    Future mods... Detriot tru-trac, deviels own stage 2 meth kit, MORE BOOST!!!!!!!!!!!!!!

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