Discovery 1 V8 Spider bypass

Hi all,

I've been reading the many threads all over the place on the infamous Spider and the problems it can cause. I have a '96 V8 Disco 1 which is sadly suffering from the advanced stages of tin cancer, but my plan is for it's heart to live on in a Defender. The Disco has a fully-working Spider and immobiliser fob but I don't want to take those over to the Defender.

I don't know whether I'm making too much of the job, but in order to transfer the ECU and all the necessary sensors and relays, my intention was to take all of the front part of the loom from the Disco and move that all over, then once I get it running in the Defender I'll chop out the parts of the loom which I don't need.

I guess there may be a simpler way but is my best solution as simple as adding in the Spider bypass across the three sets of connections? And if I do that, will the Disco still start and run until I take it apart? I want to get as much sorted before the transplant so that I don't leave myself open to problems with that.

Just to confirm, if I put jumpers on pins 2-3, 4-8 and 6-10, that's the correct requirement?

I also noticed that the Spider unit on mine is probably not original? It's cylindrical in shape, part number YWJ500020, which seems to be a replacement unit (costing about £350!!) so I guess someone at some point has had problems with the original and fitted one of these?

Thanks chaps!

I don't see what your issue is, as you won't be transferring the engines immobiliser or any other part of the disco's security system over to the Defender.

All the immobiliser does is isolate the 12v supply to the V8s ignition coil and starter motor. I assume the starter 12v is existing and functional in your Defender, so u only have to do is add the ignition switch 'switched supply' to the coil. Simples.

Ah, I recognise that reply! I did try to respond elsewhere but apparently all my posts are moderated and it takes about 24 hours for each of my posts to be displayed.

Anyway, back on topic - my plan was to remove most of the front loom from the Disco and get it working in the Defender and then remove what I don't need, hence the question in the first place. I guess there is an easier way? But I have searched high & low and i can't find anything to help me understand how much of the Disco wiring (ECU, sensors, etc) I need to take over with me and how best/easiest to do that? This is why I want to rue out the Spider etc so that I'm not troubled by it in the Defender. I don't want to have to install the key fob sensor on the ignition barrel, for instance.

Am I making this too difficult for myself?

This copy of a Haynes wiring diagram for the V8 EFI ECU will give u an idear what's what.

Thanks, that looks fairly easy to follow, I'll have a look at that. I still want to make sure I have everything I need from the Disco before I part with the remains.

Cappo said:

Thanks, that looks fairly easy to follow, I'll have a look at that. I still want to make sure I have everything I need from the Disco before I part with the remains.

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Hope it helps, anyway keep any thing electrical as most of the stuff is obsolete now.

My cruise control failed because of an iffy ecu recently, I was lucky to find a secondhand eBay replacement at £12 as the rest were offered at £30+... so all hardwear front & rear light units, dash units, switches and of course ECUs and any motors sunroofs windows etc, so anything that has wires attached to it don't let go... eBay it.

Hi discool, sorry I haven't responded sooner to this. Started a new job and have had to stand away from toys and projects for a while.

I've done a little bit more work and pulled through into the engine bay the ECU & relays, with the intention of (as per my original post) of making sure I can get the engine running in situ and independent of the Disco's wiring, just for peace of mind before I start the main transplant work. That front loom does include the spider plug but from what you said above, I think/hope that I can still wire the ECU up and get the engine running without that interfering. I think that apart from providing the power feed and the ignition live (from the coil?) then the only other connections I need are to make sure the fuel pump is fed (someone has hacked that about and apparently run a separate wire to it, chopping off the white/purple coming out of the fuel pump relay ) and then to feed the starter solenoid. I really hope its that simple!

By the way, point noted about electrical parts. The spider, for example, appears to be an aftermarket one (it's cylindrical) and when I googled that, someone paid about £350 for it! I believe pretty much everything else works (or did, before I pulled it apart) so there should be some worthwhile parts to keep.

Hi again Cappo, so your feed from the ignition switch or the fuse box if you using the discos fusebox, coil live feed is from position 2, and starter cranking is from position 3.
The EFI ECU controls the fuel pump via the fuel pump relay, that’s from terminal 16 at the ECU and via a ‘blue/purple’ wire to the relay as u can see in the diagram in post#3.
I’ve no idea why any wiring should be modified as you have said perhaps there was issue with the purge valve.

Thanks discool. It might be another week before I get time to rig this up but I'll post back here after!

Hi Discool (and all!). Just reporting back as I said I would. I'm pleased to update that.....drum roll..... we have a running 3.9 V8

As above, I have everything lying loose in the engine bay, so effectively the engine is standalone from the rest of the car (except for the fuel pump), and today I've had it running. Second attempt, I missed a wire out of the equation the first time, but today when I connected it to a battery, I heard the fuel relay click and heard the pump prime, so I was optimistic, and away she went.

Running slightly rough, that may be because it's been standing and the petrol is a bit old, or it may be due to the lack of a speed sensor for the tickover, but at least now I know it runs, so I can set about dragging it out of the car and cracking on with phase 2.

Thanks for all the help, I don't doubt I'll be back asking dumb questions again before this is all over though!

It a “Well Done” then Cappo, and yes keep in touch with the Forum.

Hi Discool and all. I said I'd keep in touch - well, the V8i into Defender project stalled for a while but I'm back on it now and I'm pleased (well dead chuffed actually!) to say that I now have a running 3.9i V8 in my Defender! Still a lot to do but I had it running this week. I haven't driven it yet, not even put the props back on, but that may be a job for this weekend.

May need to start another thread for my next question, unless anyone spots this and can help, but can anyone tell me where they located the ECU on a similar conversion?

I've read that the Range Rover loom is longer than the Disco loom and allows it to be fixed to the rear bullhead but I have the Disco loom so that's not an option unless I shell out for a RRC loom and rewire everything. Failing that, I'm thinking of either in the battery box or somehow lifting the cubby a little and putting it under there. I will also have to fab a new transmission tunnel from a mix of the old Landie one and the cutouts from the Disco which I chopped out, so somewhere on top of there might be an option unless it gets in the way of the fusebox. I remember reading somewhere that someone had put theirs under the steering column but it's not a small thing and I think that would be awkward there. Have to be mindful of not drowning it if I go through a big puddle or a ford too I guess.

Any suggestions would be v welcome, thanks.

Hi Cappo, nice to read of your V8 progress.
Use the existing loom, and mount the ECU in a dry, cool and accessible place, u may have to remove it at some time. I don’t think there’s another option.





Sent from my iPad on a train

Latest update. Progress remains slow, life gets in the way, but.....I now have a Defender which moves under it's own 3.9i steam. Only been along to road and back but it's another milestone met.

Received all the parts to fabricate the exhaust today so that's the next part of the project. I'm in the middle of making up a transmission tunnel/gearshift mount, then it's a case of wiring up the more fiddly things such as the Park/Neutral start inhibit, and then getting ready for MOT.

Have u been assent for three months? If so welcome back

discool said:

Have u been assent for three months? If so welcome back

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It's a long slow process! I don't get a lot of time to spend on it, so it's small steps when I can....

Just noticed you're in Kent - me too. ME19.

Cappo i have read through this thread and just wondered what year your disco1 was

I will be looking at doing a similar custom wiring loom, did you keep all the sensors on the engine?

I have 1 3.9 on carbs in my project car but want to keep the efi system and convert to lpg

Hi Luke, the discovery was a '96, 3.9i with the 14CUX setup. Yes , I've kept all the engine sensors. Basically I have all of the engine loom, plus there is also a short loom on the gearbox with a square plug, it's worth cutting that off in the engine bay as you'll need some of those cables too.

I have half an idea how the 14CUX works now but Im not expert enough to know what sensors you can get away without. And you'll need things like the stepper motor, and maybe the MAF (some say you can run without that but my old RRC wouldn't run without one). So for instance whilst I've wired up the water temperature and oil pressure light to the dash with the defender wiring, I've also left the water feed to the ECU in place, and I need to find the connectors for the transmission fluid temp. I had to make up my own start inhibit via a relay as there wasn't enough of the Disco loom there for that. I'm also told that I need a feed from the gearbox to the ECU to tell it when it's in neutral - I haven't done that yet and it seems to run OK.

Although my original post in this thread was about the spider, I have worked out (often with Discool's excellent help!) quite a bit of it as I've gone. Feel free to fire away with any other questions!

Im no where ready to task it just yet, have the full disco as a donor just want the smallest amount of wires possible, going to run a custom loom in the project aswel bit of a challenge, current engine runs in there but gearbox has bad oil leak

Afternoon all, hope you're enjoying the sun and not feeling too locked down!

It's almost two years since I first posted this thread (unbelievable, where the flip has that gone!!) but I'm pleased to report that I now have a running, driveable, and MOTd 3.9i V8 Auto Defender! There were a lot of conundrums to work around along the way, but despite flagging halfway through and pondering whether anyone wanted a £500 V8 Auto project, I stuck with it and got there in the end. Proud to say I did every single last nut, bolt and screw myself, on the drive not in a workshop or even a garage. There are a few niggles to sort but now it's up and running I can work on those as I go.

Thanks again to everyone who has helped with this, it really has been much appreciated.