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Thread: Operation 258 High-Output: 4.0 head swap conversion on the 4.2L

  1. #31
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    Re: Operation 258 High-Output: 4.0 head swap conversion on the 4.2L

    Quote Originally Posted by TanTJJim View Post
    Congrats! That has to be a load off finally getting it running!

    I don't have any suggestions for the diode or code 14 as I used a completely different alternator, but I have a thought on the tach. Are you trying to use the factory tach with the tach signal from the PCM? If so, it won't work as the PCM's tach driver isn't strong enough to drive the YJ's tach. What I've found that works well is tapping into the negative side of the ignition coil, you'll be able to get a tach signal from there no matter which one you want to use.
    Thanks how you did mine Jim!!! Tach works great.

  2. #32
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    Re: Operation 258 High-Output: 4.0 head swap conversion on the 4.2L


    I always wondered what this green with white stripe wire went to, since I couldn't remove the old distributor cap from the harness due to this being connected to it...

    Spliced into the negative end of the coil plug just as you said, works like a charm!! Thanks again!

    Now that black box connected to the newer alternators, how does that setup work? I have one of those and I was thinking about connecting that to my alternator just so that code 41 doesn't show up anymore but it doesn't bother me too much

    EDIT: run a 1K ohm resistor between the two alternator sensor wires (the two center prongs on the black box I think) to clear code 41
    Last edited by JD Night Fox; 10-29-2017 at 05:03 PM. Reason: update solution

    bsns. Just got srs.

  3. #33
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    Re: Operation 258 High-Output: 4.0 head swap conversion on the 4.2L

    Took it out for a test drive around my neighborhood, all the gauges are working okay. It seems to misfire once every few revolutions, there was a point driving down the street where it felt like it lost all the power and then it stalled and I had to turn it over 3-4 times to get it running again. After that it ran okay

    bsns. Just got srs.

  4. #34
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    Re: Operation 258 High-Output: 4.0 head swap conversion on the 4.2L

    Not sure what black box you're talking about. There is something like that that they XJ's used for the alternator but it looks like it's been cut off on your harness. if it were there the black deal for the newer alternator just has a couple wires in it and locates the terminals for the alternator. I'm using an older GM style alternator on mine so I used the Green/Orange wire to supply the field current and cut the other Green wire. It looks like you have the Green/Orange and Green wires but the rest of what should be there has been cut. If I were you and a GM style alternator fits your brackets I'd just use that and deal with the code or make what you have now work.

    I'm pretty sure the Green/White wire you have is related to the A/C system, I cut all that stuff out too.
    Last edited by TanTJJim; 07-07-2015 at 09:26 PM.
    I'ma cookin' somethin' up!

  5. #35
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    Re: Operation 258 High-Output: 4.0 head swap conversion on the 4.2L

    Quick update, pulled off the transfer case today and the auto tranny won't stop leaking out of the rear seal. Is the seal bad or is it supposed to have fluid inbetween the spot where it mates the two?

    It also poured out ATF from the rear transfer case seal when I pulled the drive shaft yoke out. .......is that seal leaking too?
    Last edited by JD Night Fox; 07-18-2015 at 06:21 PM.

    bsns. Just got srs.

  6. #36
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    Re: Operation 258 High-Output: 4.0 head swap conversion on the 4.2L

    Quote Originally Posted by JD Night Fox View Post
    Quick update, pulled off the transfer case today and the auto tranny won't stop leaking out of the rear seal. Is the seal bad or is it supposed to have fluid inbetween the spot where it mates the two?

    It also poured out ATF from the rear transfer case seal when I pulled the drive shaft yoke out. .......is that seal leaking too?
    post up some pics playa
    1966 Mercedes Benz Unimog 404.1
    2001 Dodge Dakota on roids

  7. #37
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    Re: Operation 258 High-Output: 4.0 head swap conversion on the 4.2L




    These two points are where the fluid came out of. Is that normal when you separate them? The transmission was producing a constant drip out of that spline

    bsns. Just got srs.

  8. #38
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    Re: Operation 258 High-Output: 4.0 head swap conversion on the 4.2L

    Quote Originally Posted by JD Night Fox View Post


    Update#4!

    Here is the engine bay fully assembled, aside from the PCV inlet and the air vent for the charcoal canister, which I need some rubber hose from the hardware store to hook up. The airbox isn't mounted to anything so I need to figure out how to get that held down. The YJ airbox mount was spot welded to the fender so I would have to saw one off and bolt it onto mine or something.
    I have a YJ 4.0 airbox with all the tubes, piping and the mounting bracket if you need it....

    Scott
    '93 YJ, 4.0, NV4500, Atlas, 35s
    '17 WK2, 5.7, ZF8HP70, NV245, 31s

  9. #39
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    Re: Operation 258 High-Output: 4.0 head swap conversion on the 4.2L

    You know that mounting bracket would be nice, actually

  10. #40
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    Re: Operation 258 High-Output: 4.0 head swap conversion on the 4.2L

    Quote Originally Posted by JD Night Fox View Post
    You know that mounting bracket would be nice, actually
    Whole thing is yours for a 12 pack.
    '93 YJ, 4.0, NV4500, Atlas, 35s
    '17 WK2, 5.7, ZF8HP70, NV245, 31s

  11. #41
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    Re: Operation 258 High-Output: 4.0 head swap conversion on the 4.2L

    Quote Originally Posted by TreeKiller View Post
    Whole thing is yours for a 12 pack.
    Tempting...

    I'll let you know next time I'm in town, what flavor is your demise
    Last edited by JD Night Fox; 07-22-2015 at 07:38 PM.

    bsns. Just got srs.

  12. #42
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    Re: Operation 258 High-Output: 4.0 head swap conversion on the 4.2L

    Miller lite or PBR cans.....
    '93 YJ, 4.0, NV4500, Atlas, 35s
    '17 WK2, 5.7, ZF8HP70, NV245, 31s

  13. #43
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    Re: Operation 258 High-Output: 4.0 head swap conversion on the 4.2L

    Quote Originally Posted by TreeKiller View Post
    Miller lite or PBR cans.....
    I'm going to be in town sometime this week so read your PM's or I'll have to break into your house and steal it myself

    bsns. Just got srs.

  14. #44
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    Re: Operation 258 High-Output: 4.0 head swap conversion on the 4.2L

    Quote Originally Posted by JD Night Fox View Post
    I'm going to be in town sometime this week so read your PM's or I'll have to break into your house and steal it myself
    LOL OK OK you got my attention! If you do break into my house, just leave a bunch of college girls behind when you're done. No harm no foul

    Scott
    '93 YJ, 4.0, NV4500, Atlas, 35s
    '17 WK2, 5.7, ZF8HP70, NV245, 31s

  15. #45
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    Re: Operation 258 High-Output: 4.0 head swap conversion on the 4.2L

    Update day 33

    The MAP sensor decided to not get any voltage again, so I've had enough of its attitude and chopped up the wiring harness to find the short

    It turns out the 5v power supply is spot welded to all the sensor wires to branch off to them, but because of the wires being old they separated so I had no connection to 5v power for the MAP sensor

    I spliced them back together with a butt connector and now I'm getting 5.02 volts at the sensor plug. Looks like this 4.0 swap can finally come to a close, once I get a fuel pressure gauge so I can monitor the pressure during different driving conditions

    Also, I bought a vacuum tester for $40 from O'Reilly's to check all my intake connections so I don't have any leaks, and sure enough I found a disconnected vacuum line on one of the ports that I fixed, as well as a few loose rubber connections between hoses for the vacuum reservoir and other things. This came in handy pretty well.

    bsns. Just got srs.

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