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Scott Ganimm
Scott Ganimm

(1 posts)

09/29/2018 06:11PM

Main British Car:

Can I convert a Range Rover Flapper EFI to 14CUX EFI
Posted by: Scott Ganimm
Date: September 29, 2018 06:28PM

I would like to convert our 3.5litre EFI 1989 RRC from the flapper EFI to the more reliable Hotwire EFI system. But before we do anything I need to be sure that this will all work as the flapper system is running well but feel the hotwire system would be more reliable and efficient.

I also have a 1989 RRC with the 3.5 litre EFI flapper type injection system and I am having trouble with the idle hunting when hot and the car blows out a lot of black soot when cold until the choke deactivates. I was wondering if you know if I could change over this car to the hotwire injection system. I do have a spare hot wire 14CUX ECU and MAF, wiring harness, plenum (but not the manifold). Could it be as simple as installing these and or using the existing wiring harness in the car as the big multi plug to the ECU looks the same but the plug on the MAF is different? If not what would I need to do or is there any other options for my issue?

My queries are as follows:
Will the old 3.5 plenum work or will we need to use the plenum from the 3.9. if we need to use the 3.9 plenum then will it fit over the existing manifold as the kit did not come with a manifold
Will the wiring harness integrate with the existing instrument panel so the relevant lights will light up if there is any issues
Will there be space for the ECU and wiring as the car is very original and in good condition so I want to make it look like it was done from the factory
Do you have the software to access this hotwire ECU to tune etc..?
Are there any other options to upgrade the ECU and EFI system from the flapper system other than what I have?
As we have two RRCís (one EFI 3.5 and the other 3.9 EFI) I have had a good look at both cars and compared the 3.5 motor against the 3.9 motor and have the following queries to add:

1. The 3.9 manifold has a coolant temp sensor as well as a temp gauge sensor however the 3.5 manifold has a coolant temp sensor and a Thermo Time switch sensor for the cold start. How will this work with the hotwire system and how will the dash temp gauge get a signal? Does it get it from one of these sensors now on the 3.5 or is there another sensor I am missing for the temp gauge?

2. On my 3.9 motor the wiring harness seems to go through the firewall in the centre behind the motor just above the bell housing. This is a very awkward positon especially if we have to remove the dash on the inside to enable us to run the new harness. Can you find out if I am correct? If I am correct maybe we need to consider blanking off this hole and boring a new hole in the firewall near the driverís side and running the new harness into the inside where we will be positioning the ECU etc.Ö

3. We will need to consider what gaskets and pipes we need so maybe compare the new and old systems in the parts book so you I am prepared

4. Maybe I try to assess if we can partially install this upgrade without going through the firewall to see if it will all work first

5. How does the ECU get power

6. How does the ECU get the trigger for the injectors to open and feed fuel into a particular cylinder as I canít see how this timing is triggered in the wiring loom

7. Will the old coolant temp sensor work on the newer hot wire system
8. Do I need to install the speed transducer and is this possible to retrofit to the Flapper car with its cable set up

Attached are some photos of the 14CUX kit I have purchased which seems complete less the manifold and speed transducer and cables for the speed transducer. Any advice and help on the above would be greatly appreciated and let me know if itís possible to do this upgrade as I donít want to molest a good working original car until we know it will all work.


Edited 2 time(s). Last edit at 09/29/2018 06:39PM by Scott Ganimm.

Ivor Duarte
Gloucestershire UK
(993 posts)

02/11/2010 04:29AM

Main British Car:
1974 Land Rover Lightweight V8

Re: Can I convert a Range Rover Flapper EFI to 14CUX EFI
Posted by: 88v8
Date: October 03, 2018 05:27PM

Bad cold idle, possible fix here [www.lrukforums.com]

Old discussion in another place about (not) swapping to hotwire, here [forums.lr4x4.com]

Antique injection systems are fine until they're not. Unless you can diagnose all the inevitable old-age problems. the simpler the better.


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