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YJ 4.2 question

Discussion in 'Quitters' Club' started by FinoCJ, Jun 26, 2015.

  1. FinoCJ

    FinoCJ 1970 CJ5 Staff Member

    Does anyone know if the 4.2/258 that came on early YJs ever had fuel injection or only carb. I am thinking the inline 6 didn't get FI until the 4.0 but not 100% sure.

    thanks
     
    FinoCJ, Jun 26, 2015
    #1
  2. rejeep

    rejeep Well-Known Member 2024 Sponsor 2023 Sponsor 2022 Sponsor

    carter bbd carb only..
     
    rejeep, Jun 26, 2015
    #2
  3. Long&Low

    Long&Low Active Member

    Ifn' I remember right didn't the 1989- 1990 have a 4.0 with Renix FI?, 1991 the 4.0 went to MPFI, and all 4.2 have the carter?
     
    Long&Low, Jun 28, 2015
    #3
  4. FinoCJ

    FinoCJ 1970 CJ5 Staff Member

    I remember at some point the 4.0 was improved and termed "high output 4.0" which may have been when the MPFI was used.
     
    FinoCJ, Jun 29, 2015
    #4
  5. hudsonhawk

    hudsonhawk Well-Known Member

    The Renix FI was problematic as well. The MPFI was much more reliable. That being said it is pretty easy to build a fuel injection system for the 4.2 using a GM throttle body.
     
    hudsonhawk, Jun 29, 2015
    #5
  6. rejeep

    rejeep Well-Known Member 2024 Sponsor 2023 Sponsor 2022 Sponsor

    87-90 YJ 4.2L Carter BBD ONLY
    87-90 XJ 4.0L Renix FI system
    91+ HO head design (7124 casting IIRC)
    wasn't improved till 2001/2 with an updated intake manifold
    2006 was the last and one would argue best year for the 4.0L

    Renix blocks are however the strongest alloy composition aside form the Mexican 4.0L
    (if building a stroker)

    *slow morning in the office and no research done.. all from my noodle...
     
    rejeep, Jun 29, 2015
    #6
  7. FinoCJ

    FinoCJ 1970 CJ5 Staff Member

    Cheers all - Either forgot or didn't realize there was a 3 year overlap where the XJ had the 4.0 while the YJ still ran the 4.2. Been helping some family with used jeep shopping and doing a little research on the 4.0. Seems they have a better chance of finding a non rust bucket (didn't know that was an issue for such recent jeeps) here in Colo than in the Illinois/Wisconsin area they call home, but the prices are a bit more premium here as well.

    I always wanted to put in some sort of FI on my 4.2 (84CJ7) and of course I dream of it on my 225 as well (EZ-EFI maybe one day when I have the money and knowledge).
     
    FinoCJ, Jun 29, 2015
    #7