3.9 wiring

Bradisco · Jan 11, 2022

Hi guys
So I’ve built a challenge truck with a 3.9 v8 in it could anyone advice me on the simplest way to wire the engine loom into the cab I’m going to be putting a ignition switch and start button onto it, also has a black immobiliser box in the loom is that a problem?

Def90man · Jan 11, 2022

Don’t know about the immobiliser but ....

Bradisco · Jan 11, 2022

Thanks mate appreciate that

Bradisco · Jan 17, 2022

Could someone tell me what this is for , thanks

discool · Jan 18, 2022

Bradisco said:
Could someone tell me what this is for , thanks ]

Haven’t a clue at the moment, the model and year of Land Rover the engine was installed in would be handy.

kermit_rr · Jan 18, 2022

Is it a genuine loom? Doesn't look like the right sort of plug or the right colour for genuine LR.

Happy to be proven wrong though

marjon · Jan 18, 2022

Is it not what they call a “header” ? basically a connector connecting wires but not actually plugging into anything

J

v8250 · Jan 18, 2022

@Bradisco , which flavour of RV8 3.9ltr engine? They do differ though wiring is near same. Confirm engine and I'll post up wiring diag's for you

+ it's really worth reading up an how the varying plenums and ECU's work/the intricacies of the differing ECU's, tune resistors, road speed sensor, throttle pots et al. It'll make a lot of difference as to how well your engine runs.

read tech files here http://www.g33.co.uk/

and here https://www.actproducts.co.uk/category/lucas-injection-technical-data/

Def90man · Jan 19, 2022

I have exactly the same blue plug near the ecu plug as well. It appears to be as @marjon says, just a blank end for terminating wires

Bradisco · Jan 20, 2022

[1997 3.9 v8 efi 14cux
I’m only really wanting as simple wiring as possible for this setup up , and could someone please tell me wiring for coil and so on. Thanks

v8250 · Jan 20, 2022

Okay, it's best to read this first http://www.britishv8.org/Articles/Rover-14CUX-EFI.htm to understand how a 14cux hotwire works.

The ECU does not work [supply into and return feeds] the way most other ECU's work and, where closed loop ccts [not just Lambdas], requires most of the wiring and sensors to be as designed/as standard. Re' coil, it follows similar Lucas type coil/distributor set ups but you'll need to make sure you have the original distributor amplifier/type or this will throw out spark power output/timing. Here wiring diag

Bradisco · Jan 20, 2022

Thank you for this, will help a lot with the build

v8250 · Jan 20, 2022

Good luck and remember correct throttle pot type/set-up, lambdas, correct ignition amplifier [beware of upgrade snake oil performance jobbies], speed sensor must be fitted or engine will stall upon deceleration from 25mph below, and correct tune resistor.

discool · Jan 21, 2022

Bradisco said:
[1997 3.9 v8 efi 14cux
I’m only really wanting as simple wiring as possible for this setup up , and could someone please tell me wiring for coil and so on. Thanks

In that case you engine is the the last of the 3.9 Romulus engines which now had auxiliaries via a serpentine belt and is fitted to the later D1s.
Coil wiring is also show in diagram… ignoring the immobiliser link, just provide a ignition switch - switched supply (position 2)
Don’t forget the resistor (#23 in digram below) that was positioned by the coil, along with the amplifier, the coil which was fitted remotely from the distributor on a 1995-98MY disco.
This may also help u with the components for your engine plus the EFI ECU wiring diagram for the disco 1995 onwards.
https://www.actproducts.co.uk/2011/lucas-14cux-fuel-injection-system-–-installation-and-diagnostic-notes/

Def90man · Jan 21, 2022

discool said:
In that case you engine is the the last of the 3.9 Romulus engines which now had auxiliaries via a serpentine belt and is fitted to the later D1s.
Coil wiring is also show in diagram… ignoring the immobiliser link, just provide a ignition switch - switched supply (position 2)
Don’t forget the resistor (#23 in digram below) that was positioned by the coil, along with the amplifier, the coil which was fitted remotely from the distributor on a 1995-98MY disco.
This may also help u with the components for your engine plus the EFI ECU wiring diagram for the disco 1995 onwards.
https://www.actproducts.co.uk/2011/lucas-14cux-fuel-injection-system-–-installation-and-diagnostic-notes/

Do you know if this is something I need to keep for my transplant? It’s got wires and vacuum pipes going to it but if I don’t need it I would bin it

discool · Jan 21, 2022

Def90man said:
Do you know if this is something I need to keep for my transplant? It’s got wires and vacuum pipes going to it but if I don’t need it I would bin it

Afternoon

N0 you don’t need it. Its fitted first as part of emissions spec required at the time UK US + Japan I believe.
Basically it filters or absorbs the fumes via the petrol tank breather, then allows them into the engine when started to be burnt… hence the electrical connection.
There’s info on the web on “exactly what happens” which i read once years ago, apparently the filter requires changing, but the one on my disco is never touched, also its nothing to do with exhaust emissions.

So just blank the pipe entrance into the plenum chamber.

Def90man · Jan 21, 2022

discool said:
Afternoon
N0 you don’t need it. Its fitted first as part of emissions spec required at the time UK US + Japan I believe.
Basically it filters or absorbs the fumes via the petrol tank breather, then allows them into the engine when started to be burnt… hence the electrical connection.
There’s info on the web on “exactly what happens” which i read once years ago, apparently the filter requires changing, but the one on my disco is never touched, also its nothing to do with exhaust emissions.

So just blank the pipe entrance into the plenum chamber.

That’s great thanks

One less thing to squeeze under the bonnet

v8250 · Jan 21, 2022

discool said:
Afternoon So just blank the pipe entrance into the plenum chamber.

Is the ECU expecting to read a constant/variable resistance across the connector return to ECU pin out?

ps nice clean engine bay

discool · Jan 21, 2022

v8250 said:
Is the ECU expecting to read a constant/variable resistance across the connector return to ECU pin out?

ps nice clean engine bay

Unfortunately there are a few sensors using a variable resistance, so which one are u interested in.

v8250 · Jan 21, 2022

discool said:
Unfortunately there are a few sensors using a variable resistance, so which one are u interested in.

Your previous post re' the charcoal filter.

I've used/rebuilt/re-spec'd a good number of RV8's but none with this filter [return to ECU pin outs]. 14CUX normally requires some level of resistance adjustment from its sensors back into the ECU to ensure correct fuel map sector. So am intrigued what figure the ECU is expecting 1. with filter installed, 2. filter removed/blanked off

3.9 wiring

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