1. #1

    Question Help fuel injection for a 4.2

    My friend has a 90 YJ w/ a 4.2 automatic. I have a 96 grand Cherokee with 4.0, fuel injection and auto trans. (bad engine)

    What I would like to do is swap all the fuel injection parts to the YJ. What problems will I face? Has anyone out there done this? Will I have to use the 4.0 heads? As far as the crank position sensor, can I use the 4.0 fly wheel and just install a bung in the YJ's transmission or do I have to use the Cherokee's trans? This seems like a pretty straight forward swap. I would just love to know about any surprises that I would encounter in this swap.

    Any help would be great.

  2. Re: Help fuel injection for a 4.2

    You will have to use the 4.0 head with your fuel injection. You will also have to mount the crank position sensor to the 4.2 trans and flywheel. Not sure about the specifics on mounting the CPS or if there is a kit. A google search may help in this area.
    Safety yellow and Handicap blue CJ with 5.3 Vortec/TH400/Tons/Atlas/Roks/Locks and Airshocks.
    1622 Miles from Moab.

  3. Re: Help fuel injection for a 4.2

    What did u end up doing? Iam very interested in doing the swap myself but dunno exactly what it involves.

  4. #4

    Re: Help fuel injection for a 4.2

    Quote Originally Posted by nica89yj View Post
    What did u end up doing? Iam very interested in doing the swap myself but dunno exactly what it involves.


    Have not done anything yet. A few other projects came up and I'm doing as much research on this as possable before I start it. I will add to this as soon as I decide what direction to go.

  5. Re: Help fuel injection for a 4.2

    o..thats cool. Iam actually getting ready to do the 4.0 head swap on my 89 yj, my engine runs strong and i dont want to change to anything else. If i could put the EFI system on the 4.2 it be great, since iam gonna already have the 4.0 head in there. Ive read about yanking a computer here..taking this from there..but have not yet read a good solid write up on the EFI installation. Sometime next week iam gonna go to the junk yard and get a 4.0 head and 4.0 headers (if they come out). Iam also gonna be getting a ford 8.8. Any special tools required to remove the head? any tips? dont really know what to expect.

  6. #6

    Re: Help fuel injection for a 4.2

    It's really been a long time since I've worked on a jeep 6cyl. I don't think you will run into anything that standard tools couldn't handle. As far as the swap goes, this site http://www.hescosc.com/shop.asp?catID=7533 has some great parts to help ease the pain. The CPS kit that moves the sensor to the balancer is a great idea and what I'd plan on if I do this swap. That way you keep you trans and every thing stock.

    Good luck.

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