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Thread: WTB ECU 1990 RR Classic 3.9

  1. #1
    Join Date
    Mar 2010
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    Banner Elk NC
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    Default WTB ECU 1990 RR Classic 3.9

    Back tracking a no spark issue. My mechanic believes it's at the ECU. Does anyone have a used ECU from a running RRC to sell?
    I believe this ignition only has advance no retard function.
    Thank you.

  2. #2
    Join Date
    Oct 2011
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    Mountains of Western Pennsy.
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    You have a "14CUX" ECU. Pretty much any Range Rover or Discovery 14CUX ECU should work from 1990 to 1995 (they have numbers like: PRC-7081 or 8742 or 9060). Check the passenger side under seat on board code reader, you'll probably have to take the bottom trim off the seat to see it, it faces the door. The number codes read out one at a time, so clear one and move on to the next. You will have to find an on-line source to translate these into English. Hope this helps...

    '99 Disco II
    '95 R.R.C. Lwb (Gone...)
    '76 Series III Hybrid 109
    '70 Rover 3500S

    As a second thought... Did you check your Lucas electronic module in the distributor? They as famous for failure.

  3. #3

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    Ecu has nothing to do with spark, spark controls injector pulse thru ecu. ecus are bullet proof, I had sunken those things in muddy water, removed and rinse with clean bottled water, dried with napkins and on board compressed air and kept on running.

  4. #4
    Join Date
    Mar 2010
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    Banner Elk NC
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    Thanks for the reply. A friend has had his RRC at 2 shops for months at each. The first shop is a good import car shop the second is a long standing independent Land Rover shop. No one can get the spark plugs to fire. Last I heard a new ignition switch was going in. I think they wanted to swap ECU's just to rule it out.

    I'll post the fix when it happens.

    pb

  5. #5
    Join Date
    Oct 2011
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    Another thing I just remembered is that there is a 'White' wire on the ignition coil that allows the fuel injection to work. If it's not connected the vehicle will start and then die in a few seconds, this is to prevent an over rich condition in case of starting failure.

    '99 Disco II
    '95 R.R.C. Lwb (Gone...)
    '76 Series III Hybrid 109
    '70 Rover 3500S

  6. #6
    Join Date
    Oct 2007
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    N.H.
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    68

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    I think the white wire you are referring to is the lead from the coil to the ECU. If memory serves me correctly this supplies a signal to the ECU to let it know that the engine is cranking. If it doesn't get this signal it will not supply power to the injectors so you actually have a no fuel condition. The lead in question has a 6.8K ohm resistor in it the connectors of which can get severely corroded. The resistor is wrapped up in the wiring harness that is close to the mass air flow unit. Just follow the lead from the coil (I think it's actually white/black) and unwrap the harness and you will see what I mean. The resistor is a small rectangular black thing with a spade connector at each end. To test you can just by-pass the resistor by unplugging both connector and joining them together. If it works you should replace the resistor - I just bought one at Radio Shack and soldered in the circuit as I couldn't find a source for the original. It's about 14 years or more since I diagnosed this on one of my RR's (unfortunately long gone).

  7. #7
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    Great info guys, as of right now the truck has spark but is not getting fuel. It will run for a bit on starter fluid. The second Rover shop made some progress and we now have spark but that shop has not had much interest in working on the car since then so we figured we will just pick the car up and troubleshoot in our free time. That white/black wire sounds like a great place to start. I have recently purchased a RRC with 300tdi so today I ordered the big RRC service manual from our hosts which looks like it has a nice section on fuel injection and info I need to get my power windows and sunroof working on my truck.

    Thanks for the help, I'll keep you posted.

    pb

  8. #8
    Join Date
    Oct 2006
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    1,199

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    Oh boy those shops must be manned by the least knowlegable Rover techs on the planet if they are swapping ECUs. If you were near me I'd have you going in a matter of hours and I'm not even a mechanic!
    The ECU gets spark signal from the White with black wire that is attached to the coil. Be sure this wire is connected firmly as they tend to weaken and fall off over time. The white wire is your tachometer signal wire and goes to the dash. The two wires that are transmitting spark timing to the coil is the blue and white wires coming from the ignition amplifier module. The distributor creates a (very weak) electrical pulse that the amplifier module bumps up. This is sent to the coil where it is further amplified and sent to the spark plugs.
    The ECU also uses this pulsing signal to time the injector events. If it is not getting this signal input you will not get fueling events.
    You can see if the fuel pump is working by turning the key to the run position and have someone back near the tank listen for the pump to come on. This will let you know whether you need a new pump.
    So, to recap, if no fuel, check for the white/black wire and the fuel pump. This includes the tuning resistor inline with the white black wire but those rarely go bad.
    No spark, usually it's the ignition amplifier module. Or coil, or cap rotor, or primary coil wire to cap.
    ALWAYS keep a spare amp module, cap and rotor with you.

  9. #9
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    Thanks for the tips, you sound like a pretty solid mechanic to me. I'm waiting on the car to get back to Boone but I have been saving information and tips like this so I can help my buddy. I'll be sure to report our results.

    Thanks again pb

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