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    Thread: Mk1 caddy to 1991 8v engine swap.

    1. 09-19-2019 11:34 PM #1
      So I looked for a wile on here in the mk1 and mk2 forums and cant find what I'm looking for so figured I'd just ask.

      I'm swapping a 1991 8v 1.8l gti engine into a 1981 caddy. The guy who owned the new engine before me cut a bunch of wires and I just need to know exactly which relays and wires I need from the fuse box to make it run. As long as I can get it running I am sure I can figure the rest out myself.

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    3. Member rabbitnothopper's Avatar
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      RIP81. 78 VW Rabbit 1.5L EH 4speed 020 GC->GP, 82 Rabbit Pickup 1.6D
      09-20-2019 12:25 AM #2


      buy manual for both cars

      done


      ... but realistically its just plug n play
      not much changed between a 1.6/1.7L from your 1981 pickup
      to
      the 1991 1.8L engine

      just reuse whats on the 1981

      .... unless ...
      your pickup was diesel.....

    4. 09-20-2019 01:20 AM #3
      It was lol. So it didnt even have a brain box like the new one does.

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    6. 09-20-2019 01:56 AM #4
      I've also gone through a few manuals. And not one has told me what these relays even go to. Let alone which ones are required. They all just say there is a relay. Most dont even give what fuse the line should have. So looking at this mess of wires infront of me theres still nothing that has been the least bit helpful. Cause I dont know what goes where to begin with. The relays. So all it's been so far is trying to look at the wires coming from a relay and trying to match the wires with what the diagram says. And when it doesnt have enough wires or there thr wrong colors or run from the wrong side of the relay I move to the next. So if all i can use are these useless manuals i might as well just try to wire it totally by me self. Which will take ages with it already not running. If I could just get the help I need to make the thing run I could trouble shoot the rest myself and make my own wiring harness and fuse box. I just want a starting point that isnt going to add a few months of trial and error to this presses

    7. Member jiffyjetta's Avatar
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      09-20-2019 02:23 AM #5
      This site should help you out. I've done many swaps over the years using it.
      http://www.a2resource.com/
      Last edited by jiffyjetta; 09-20-2019 at 02:30 AM.
      Tuned mk6 2.0t CBFA 6 speed ECU for sale. Launch control set @ 3800 & 8psi, immobilizer delete, cat delete, air pump delete. $300 shipped.

    8. 09-20-2019 03:07 AM #6
      Thank you so much. In less then 5 minutes that website has been more usefull then the manuals I've been using for the last 3 days.

    9. Senior Member briano1234's Avatar
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      09-20-2019 07:49 AM #7
      The 81 rabbit/caddy was Westy built, the Cabriolet was German built, different fuse boxes.

      www.cabby-info.com has a listing of the relays and pinouts, as well as the locations in the Cabriolet fuse panel, any wire you splice should be soldered and heat shrinked.

    10. 09-20-2019 11:08 AM #8
      Rewiring a car to accept your new engine is really not that difficult. A bit of understanding how the new engine computer works [and what it needs to work] and an understanding what your car has is all you need.

      There is no Bentley or any other manual that will tell you which wires to hook up. Basically the ECU needs 30, 31, 15, and maybe 50 [power, ground, ign, and starter].

      It can be a time consuming job, but certainly not difficult, if you can read a wiring diagram and understand how solder works. Start with one wire at a time. Each wire you do must be correct before you start with the next one. At one point of time, you'll be done. Simple easy.

    11. Member rabbitnothopper's Avatar
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      RIP81. 78 VW Rabbit 1.5L EH 4speed 020 GC->GP, 82 Rabbit Pickup 1.6D
      09-21-2019 05:30 AM #9
      Quote Originally Posted by Guss mk1 Caddy View Post
      swapping a 1991 8v 1.8l gti engine into a 1981 caddy.
      nothing here says cabriolet.
      ...

    12. 09-21-2019 07:44 PM #10
      This is what I was looking for here. 30, 31, 15 people who have some onsite of what is and isnt needed. It's been a fairly difficult process find this kind of information. Thank you.

    13. 09-21-2019 07:58 PM #11
      It's just been a little hard finding an accurate wiring diagram for these things. Even the A2aresourse website is a little strange to use because I cant find the correct fuse box on it. My system seems very different from all the ones on that website. I really just need to find the. Ignition and starter wires. The ground and power should be really stiat forward. But I'm literally just starting with a bunch of random wires in a fuse box. I have no idea which are to the battery which is to the starter and which is the key cause most of the wires have been cut from there plugs. So I have almost no reference points other then diagrams. Which i still haven't managed to find one that is correct for the car. Even going as far as to try Haynes and Chilton's manuals. It's almost as if I found a weird model. Nothing matches exactly. If I could just find a wiring diagram that was exactly like mine I'd probably be done already.

    14. Member rabbitnothopper's Avatar
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      RIP81. 78 VW Rabbit 1.5L EH 4speed 020 GC->GP, 82 Rabbit Pickup 1.6D
      09-21-2019 10:17 PM #12
      well basically...
      http://chris.chemidl.in/vw-wiring-di...982-1983-1984/

      81-84 barely changed, you'll find some random notes for things
      but its all the same...


      or a bentley manual, which also has wiring diagrams, some of them in color



      feel free to take pictures
      post them on IMGUR or something
      and copypasta the ]img[ code ]/img[ here

    15. 09-21-2019 11:01 PM #13
      Ok but I need help with the 1991 end of things. The 1981 was fully intact so I know all of it. The 1991 is where then engine and wiring harness is from. I'm just having problems getting the power ground and ignition from those. Also my computer is a 38 prong. So there is no prong 50. I just need to get my CPU power ground and ignition. And I cant find them cause everything I'm expecting to connect to doesnt even connect to the ecu. I tryed using my meter but its says nothing when I connect it to red or black wires and try every prong on the wiring harness.

    16. Member rabbitnothopper's Avatar
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      RIP81. 78 VW Rabbit 1.5L EH 4speed 020 GC->GP, 82 Rabbit Pickup 1.6D
      09-22-2019 10:47 AM #14
      referring to some topics here

      your pickup was a diesel?

      your wiring from the fusebox is diesel
      your fuel system from the tank is diesel


      the 91's 1.8L was gasoline?
      it was digifant fuel system?

      you need the digifant fuel system & wiring
      or, change to the 1974-1989's CIS fuel system & wiring
      changing to CIS would require a different head (digifant is moddable to CIS on the head?)


      to summarise:
      you need ignition and sensors from the fusebox to the engine
      you need fuel system that is compatible


      yes?


      ignition module
      ignition coil
      ^ most basic things
      sensors and switches
      ^ help but not absolutely required to run the engine

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