springwood · Nov 24, 2018

Hello, I'm a newbie and don't know my way around here ( actually I'm an oldbie and don't know my way around anywhere )
I am trying to complete a major transplant of a 96 3.9efi serpentine engine/ LT77 box into a 1986 Lotus. The job was started about 6 years ago and has passed through the hands of four owners since then. It is now down to me to finish it off.
I realized that I am missing the wiring loom section which connects the distributor to the ignition amplifier. The plugs are 3 pin ( although only two used I think ) and oval in shape and seem to be very scarce.
Can anybody please point me towards someone who can help out here?
The male plug (ends ) are most important as the loom will need lengthening to about 40 inches.
Thanks in advance.
springwood.

dieseldog69 · Nov 24, 2018

springwood said:
Hello, I'm a newbie and don't know my way around here ( actually I'm an oldbie and don't know my way around anywhere )
I am trying to complete a major transplant of a 96 3.9efi serpentine engine/ LT77 box into a 1986 Lotus. The job was started about 6 years ago and has passed through the hands of four owners since then. It is now down to me to finish it off.
I realized that I am missing the wiring loom section which connects the distributor to the ignition amplifier. The plugs are 3 pin ( although only two used I think ) and oval in shape and seem to be very scarce.
Can anybody please point me towards someone who can help out here?
The male plug (ends ) are most important as the loom will need lengthening to about 40 inches.
Thanks in advance.
springwood.

Go visiting a few breakers yards and gather everything you need.

sierrafery · Nov 24, 2018

or contact this guy who knows everything about LR connectors: https://www.ebay.co.uk/str/landroverconnectors he might be able to set you up a new harness

springwood · Dec 2, 2018

Thanks for the response to my enquiry. I have searched all local breakers and a few specialist in the south and southwest to no avail. I contacted the chap whose business was on the link and he was quite helpful. The most successful result came via Rimmer Bros who put me in touch with a company in Derby who supply automotive wiring parts and materials; I was able to buy both plugs from them for around £15 incl VAT and postage.
On a different tack regarding the 14CUX ecu can anybody advise whether it is absolutely necessary to use an electronic speed sensor rather than a machanical worm speedo drive on the LT77 gearbox?
Thanks again.

discool · Dec 2, 2018

The D1 3.9 electronic speedometer and the EFI ECU are interfaced with a single transducer that is driven from the vehicles transfer box - which u won’t have - but as the subject isn’t new, the links below may help you, the links found are only very quick search of Google so no doubt there’s a bit more information to be found.

https://rimmerbros.com/Item--i-AMR3386P
https://www.v8forum.co.uk/forum/viewtopic.php?t=15139

springwood · Dec 15, 2018

discool said:
The D1 3.9 electronic speedometer and the EFI ECU are interfaced with a single transducer that is driven from the vehicles transfer box - which u won’t have - but as the subject isn’t new, the links below may help you, the links found are only very quick search of Google so no doubt there’s a bit more information to be found.

https://rimmerbros.com/Item--i-AMR3386P
https://www.v8forum.co.uk/forum/viewtopic.php?t=15139

Many thanks for the information, Rimmers have been able to supply the necessary cable driven tranducer for an LT 77 gearbox so all is well..
I have a further mystery which i hope somebody can solve for me.
The 14 CUX requires an input from a fuel purge valve / sensor. I have a wire in the ECU loom but no sign of what it might connect to . I'm assuming it's somewhere near the throttle body/ MAF but as one was not fitted to this engine when I received it I have no idea what it looks like...nor do Rimmers.
It is not the same as that fitted to the 4.2/ 4.6 later.
Any help would , once again , be much appreciated.

discool · Dec 15, 2018

Don’t worry about it, its all about emissions back then, so make safe that wire as u won’t use it. The ‘fuel purge’ is removing petrol vapor from the fuel tank and then via a charcoal canister, when the valve operates its into the plenum and then burning it. That’s as much of an interest I have as my disco is fitted with this system.

There’s info in the LR workshop manual for the vehicle with this system installed, below is quick snippet for the D1 3.9.
“During normal vehicle operation and when the engine is switched off, the venting system between the fuel tank and EVAP canister is open to allow the free passage of vapour.
The EVAP canister, which is connected by a nylon hose to the plenum chamber, absorbs and stores the fuel vapour from the fuel tank when the engine is not running. With the engine running, vapour is purged from the EVAP canister by allowing outside air to be drawn through the EVAP canister vent solenoid and link pipe by the influence of manifold vacuum to the EVAP canister purge connection on the canister”.

springwood · Dec 15, 2018

discool said:
Don’t worry about it, its all about emissions back then, so make safe that wire as u won’t use it. The ‘fuel purge’ is removing petrol vapor from the fuel tank and then via a charcoal canister, when the valve operates its into the plenum and then burning it. That’s as much of an interest I have as my disco is fitted with this system.

There’s info in the LR workshop manual for the vehicle with this system installed, below is quick snippet for the D1 3.9.
“During normal vehicle operation and when the engine is switched off, the venting system between the fuel tank and EVAP canister is open to allow the free passage of vapour.
The EVAP canister, which is connected by a nylon hose to the plenum chamber, absorbs and stores the fuel vapour from the fuel tank when the engine is not running. With the engine running, vapour is purged from the EVAP canister by allowing outside air to be drawn through the EVAP canister vent solenoid and link pipe by the influence of manifold vacuum to the EVAP canister purge connection on the canister”.

Fantastic ..thank you very much.

springwood · Jan 10, 2019

Final bits of wiring have thrown up a puzzle for me. The wiring diagram for the 14CUX shows fuel relay and main relay with a common brown wwire apparently linking them but it doesn't show the source of power to either one. Are they powered from ignition, alternator, battery or what ? Once again any helpful advice would be greatly appreciated.
Thanks.

sierrafery · Jan 10, 2019

What diagram are you watching at? I can't see any common brown wire in the 14CUX diagram

discool · Jan 10, 2019

The brown wire is the 12v feed from the battery to the fuel injection ECU. On its way it is the supply to the ignition switch, then onwards to the ECU there’s a tap-off the brown wire going in the contact of the Fuel pump relay, also there’s a tap-off to the coil and to the contact in the Main relay.
So thats it, very straight forward.

sierrafery · Jan 10, 2019

discool said:
The brown wire is the 12v feed from the battery to the fuel injection ECU. On its way it is the supply to the ignition switch, then onwards to the ECU there’s a tap-off the brown wire going in the contact of the Fuel pump relay, also there’s a tap-off to the coil and to the contact in the Main relay.
So thats it, very straight forward.

I'm aware that you know your struff when it comes to V8 D1's so my intention is not to contradict you just to help but based on the OP's first post

springwood said:
I am trying to complete a major transplant of a 96 3.9efi ...

i keep watching the '96 diagrams and what i see is NO not N wire to the main relay and ECU and nothing which contains N at the fuel pump relay, these are from the '96 diagram, what am i missing?

discool · Jan 11, 2019

sierrafery said:
I'm aware that you know your struff when it comes to V8 D1's so my intention is not to contradict you just to help but based on the OP's first post
i keep watching the '96 diagrams and what i see is NO not N wire to the main relay and ECU and nothing which contains N at the fuel pump relay, these are from the '96 diagram, what am i missing?

What your missing is the diagram for for the earlier EFI wiring loom.
The single wire colour ‘brown’ and the relay being called “main relay” are the two clues that tell it’s an early loom.
The later diagrams that your looking at have very different colour wiring with most having a coloured tracer, also with later the “main relay” is now called “engine control load relay”.

So it appears that with the OPs request in post #9, he is using the early loom, okay... but I can’t see that working with the later engine without some modification, unless the date of engine is incorrect, if its pre 95 then it will work.

So that’s it all very straight forward, one of the benefits of a petrol Disco 1

cappers · Jan 11, 2019

Not sure if this is of any help, Disco1 3.5 14CUX (??same as 3.9??) and a 3.9 wiring pdf.

Discovery Mk1 3.5 V8 14CUX Efi wiring.jpg

springwood · Jan 24, 2019

capo said:
Not sure if this is of any help, Disco1 3.5 14CUX (??same as 3.9??) and a 3.9 wiring pdf.
View attachment 167147
View attachment 167159

Thanks gents, I'm afraid I'm still struggling. Terminal 40 on ECU is fuel pump/ engine speed control / lambda sensors and apparently requires a 6.8 K ohm resistor in line.
I have been advised that it is not necessary to use the lambda sensors on this application but my local electrician can't get his head around that either.
Once again I would be grateful if anybody will shed some light on this for me.
Thanks in advance.

cappers · Jan 24, 2019

springwood said:
apparently requires a 6.8 K ohm resistor in line.
I have been advised that it is not necessary to use the lambda sensors on this application but my local electrician can't get his head around that either.
Once again I would be grateful if anybody will shed some light on this for me.

A Tune Resistor was originally specified in the wire harness so that one ECU part number could serve multiple vehicle markets. (Multiple computer programs could be stored within the ECU, and the ECU could "decide" which one to use based on what resistance it sensed.) One leg of the Tune Resister was wired to terminal 5 of the ECU, and the other leg was spliced to ground. At some point during 14CUX production, Rover apparently decided to eliminate the Tune Resistor. (According to Rover service literature, this started with VIN number LA451517.)

The following information on Tune Resistors is based on Rover service literature. Visual inspection of wire color codes will allow you to quickly differentiate between resistors:

White 3900 Ohms - USA and European vehicles with catalytic converters
Green 470 Ohms - UK and European vehicles without catalytic converters
Yellow 910 Ohms - Saudi vehicles (without catalytic converters.)
Red 180 Ohms - Australia and "the rest of the world."

All four types of Rover Tune Resistors were rated for 0.5 Watts.

Tune Resistor is connected to the ECU through terminal position 5, and connected to terminal position 27 through a splice. If you wish to check the resistor, first disconnect power to the system, second disconnect the EFI Cable Harness Assembly from the ECU, and finally simply measure resistance (using an Ohmmeter) from pin 5 to pin 27 on the main ECU connector. (Resistance isn't polarity dependent.)

From this I think if you aren't using the lambdas then you need the Green 470 Ohms resistor rather than the White 3900 Ohms. I don't know about a 6.8 KOhms one......

cappers · Jan 24, 2019

capo said:
I don't know about a 6.8 KOhms one......

Haha! There is a 6.8k Ohms resistor on the Engine Speed sense circuit. This resistor should NOT be confused with the Tune Resistor.
This circuit is the only connection between the ignition system and the fuel injection system. A damaged or loosely connected resistor would likely result in an open circuit, leaving the ECU wondering about engine speed. The resistor is marked "Lucas", "RD953066", "83630A", and "892Q". The resistor should provide about 6.8k Ohm resistance.

discool · Jan 24, 2019

RD953066 is what I have attached to my disco ignition coil, alone with a second one for use if the vehicle was a manual instead auto both have been fitted from day one undisturbed.
For more info on the resistor Google the part no. above or this forum https://www.landyzone.co.uk/land-rover/3-9-92-classic-wiring.265436/
For the tune resistor, that item can easily be seen hanging next to the ECU, well mine can as its white

springwood · Jan 26, 2019

Once again thank you all for your input. I have managed to get a resistor from Rimmers under another part number. I am , however, unable to find a supplier for the 470 ohm tune resistor. A little closer every day !

discool · Jan 26, 2019

As capo said above its just a 0.5 watt resistor, any electronic outlet will supply u with that rating.
The difference with the Factory one is it is encased in moulded plastic around 20/30mm long
The resistor no. is PRC8172, that for 470 ohm green.

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