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Coil pack rail

Discussion in 'Cherokee' started by Billy1234, Feb 4, 2020.

  1. Feb 4, 2020 at 8:39 AM
    #1
    Billy1234

    Billy1234 [OP] Well-Known Member

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    So i have a coil rail I hate that dam thing I dont have th holes for it in the head. My boss has a ranger with the coil pack and wires can I switch to somthing like that?
     
  2. Feb 4, 2020 at 12:23 PM
    #2
    CZJ7

    CZJ7 Jeep—rotating the earth since 1941

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    I’m guessing it’s an older head?? If so they are not drilled/tapped for the coil-on-plug rails. To change you would have to go with an older distributor-type system with the cam position sensor inside it under the rotor. The coil gets mounted next to it on the block. The kicker is that it would require a different CPU, one from a pre-2000. Assuming it’s a 4.0?Hope I’m reading this right.
     
    Last edited: Feb 4, 2020
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  3. Feb 4, 2020 at 2:07 PM
    #3
    Billy1234

    Billy1234 [OP] Well-Known Member

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    Yes your reading it right. The engine is from my 97 that I had. This is a 2000 jeep xj so I assume I could just go to a junkyard find a 97 auto with a distributor and switch it correct?
     
  4. Feb 4, 2020 at 2:18 PM
    #4
    CZJ7

    CZJ7 Jeep—rotating the earth since 1941

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    I think it will need the CPU that’s in the Jeep you pull the distributor out of. It’s a matter of driving one coil vs. 6 coils. Your CPU is programmed to fire 6 different coils, one at a time in sequence (firing order). The replacement distributor CPU only fires one coil and lets the distributor send that spark to the correct plug.

    Is there any way to make a bracket to keep the coil rail on the older motor? It might be a TON easier that switching up the distributor. It’s all very possible, but electronics often don’t play well with different components.

    When I get home I’ll look at an old one vs. a newer one for ideas.
     
  5. Feb 4, 2020 at 3:48 PM
    #5
    CZJ7

    CZJ7 Jeep—rotating the earth since 1941

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    I looked at both motors. IMO your best bet is to figure out how to mount the coil rail to the older motor. I looks like a fabricated bracket is your best bet. The newer head has castings specifically for the 4 bolts that hold the coil pack on. The old heads don’t have those castings, but because of that it looks like there’s room for a fabbed bracket (assuming the tops of the spark plugs will locate the rail in a good spot) on the older head. It’s a total bummer when mixing/matching different year-model motors.

    It would not only require the newer CPU, but the entire engine wiring harness as well. Sorry I don’t see an easier solution. Any 4.0 ignition gurus out there?
     
  6. Feb 4, 2020 at 3:49 PM
    #6
    Jim Beam

    Jim Beam Well-Known Member

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    Attaching the coil rail to the head might not be the best way to mount it due to the heat transfer from it. I think the coil rails were installed on the head for ease of installation, but that's just my $.02.
     
  7. Feb 4, 2020 at 4:02 PM
    #7
    CZJ7

    CZJ7 Jeep—rotating the earth since 1941

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    It’s a good point, however, Jeep, and many other manufacturers, have done it that way for years as it’s really the only way to set up coil-on-plug systems. The integrated mounting points on the coil pack/rail on the 4.0 are fairly substantial. I’m baffled that coils can withstand the abuse of engine vibration and heat the way they do. Those suckers are tough.
     
  8. Feb 6, 2020 at 9:04 AM
    #8
    Billy1234

    Billy1234 [OP] Well-Known Member

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    So I have no power going to the fuse for the pcm. What's this mean I have power at the dlc. Is the computer bad?
     
  9. Feb 6, 2020 at 9:10 AM
    #9
    CZJ7

    CZJ7 Jeep—rotating the earth since 1941

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    Crap, I would have to see a wiring diagram. If the fuse is between the power source and the battery, I would have to say the PCM is ok.
    What’s the dlc?
     
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  10. Feb 6, 2020 at 9:37 AM
    #10
    Billy1234

    Billy1234 [OP] Well-Known Member

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    Data link connector sorry was trying to be technical lol. I dont know how to tell if the fuse is between the power source and battery. Wouldnt the power source be the battery
     
  11. Feb 6, 2020 at 9:52 AM
    #11
    CZJ7

    CZJ7 Jeep—rotating the earth since 1941

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    Check both sides of the fuse housing (with the fuse removed), and make sure the fuse itself isn’t blown. If it’s ok and still doesn’t have power the only thing I can think of without seeing the diagram is move upstream. I know that sounds obvious.

    Yes, battery is the primary power source, but there could be a power distribution block in, near, or part of the fuse block.

    Is the key on and battery hooked up while checking all of this? Not trying to second-guess your procedures, just making sure. It’s a pain to trace these things.
     
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  12. Feb 6, 2020 at 9:56 AM
    #12
    Billy1234

    Billy1234 [OP] Well-Known Member

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    Yes key on and battery hooked up. I would second guess my procedures if I were you lol
     
  13. Feb 8, 2020 at 1:59 PM
    #13
    Billy1234

    Billy1234 [OP] Well-Known Member

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    Is this the correct wiring diagram? Screenshot_20200208-165816_Gallery.jpg
     
  14. Feb 8, 2020 at 2:51 PM
    #14
    CZJ7

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    That’s for the body behind the firewall. Look for one (or several in a series) that specifically state “fuel injection system” somewhere with the correct year. Haynes manuals are a pretty good resource. Be prepared for many pages—many because they break the whole thing down into several subsystems, which makes them much more detailed and easier to read. I can send the ones from my ZJ manual, but there’s 17 diagrams, just for the fuel injection on a 2000. By comparison, the 1998 (your new motor) and older systems have 6 pages. I would imagine your XJ has a similar system but not the same.
    That’s a long way of saying......umm, not quite the right diagram.

    I’m having a headache trying to find what made my ZJ quit.
     
  15. Mar 30, 2020 at 7:22 PM
    #15
    cpttuna

    cpttuna Active Member

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    If you have a 97, consider the viper coil pack conversion and get rid of the coil bar.
     
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