Thread: TD5 Harness

Rover - I have this problem right now. Although it isn't affecting my driving yet, it may soon - so I'm changing mine next week. The plug (red one) on the ECU is damp with oil and dust, a sure sign of up-coming problems. I believe that the previous owner of my 2000 Defender had the harness replaced once before - under warranty in about 2002. The problem is back again.......

The injectors are wired to the ECU via a harness that sits inside the rocker cover - immersed in engine oil. The plug that connects all of this is under the front LHS (looking front-on) of the rocker cover. The seals that prevent oil from leaking past the plug exiting the rocker cover were not particularly good on pre-03 (I think) models (hence mine still having the same problem after a change in 2002) - after which the problem should have been resolved. The big problem is that once oil enters the loom, wire by wire, up in the oil bath, capillary action makes sure that oil seeps out of the seal at the rocker cover interface. Once outside of the rocker area it just keeps travelling along the wiring harness and eventually starts to infect the main engine wiring harness. From there it just travels all the way to the ECU under the driver's seat - which is at the lowest point. Once there it soaks the plug on the ECU and starts to electrically affect engine performance - including mis-firing injectors, etc.

Apparently it's more prevalent in the Defender simply because the ECU is so low. In the Discovery it's up higher in relation to the harness - which means that oil propagation is somewhat retarded by gravity. Capillary action might eventually win here too - but it would take ages.

Hope that explains a little. The injector harness (genuine LR) is around thge $120 plus GST, so it's not a biggie - unless your entire engine loom is completely soaked.... in which case you have to do what dhumphri is doing ATM - replacing the lot.

Omaroo

thanks for the detailed explanation, I did not realise the harness and connector were under the rocker cover and engine oil emersion was the cause. Hopefully wont run into this probelm - Defender 04.

Thanks again. Thank god for the forum.

Rover

Originally Posted by rover

Hopefully wont run into this probelm - Defender 04.


Rover

Hopefully Rover.

Just out of interest, if you were to do us a favour and lift the cover under your driver's seat - is the red plug at all oily? Is the wiring sticking out from under plug at the LH edge of the rocker cover oily on yours? You'll have to remove the acoustic hood to see. Two bolts on either side of the cover to remove it.

Cheers
Chris

Omaroo

will check and let you know, probably on the weekend though.

Cheers

Rover

Originally Posted by rover

Omaroo

will check and let you know, probably on the weekend though.

Cheers

Rover

Cheers - and thanks. I'd be interesting to know how a later model is faring.

Omaroo

Checked out on the weekend.

Firstly, no sign of any oil on or around ECU plug, nor any signs in bottom of compartment well.

Actually, not sure what your harness looks like - but on mine, the harness enters about the same level as the ECU, but individual wires are separated from the grommet/bulhead seal and dip 50mm downward before entering the plug. One would think if any oil made it this far, it would drip into the compartment floor.

I did not check under the acoustic cover as yet.

Cheers

Rover

I found the oil pools in the harness connector just outside the head and then runs/seeps into the copper core of the wiring to the ecu plug. This is why a complete injector/engine harness replacement is reccommeded. The contaminant can be flushed out of the wiring with a little patience and copious amounts of contact cleaner (non plastic melting type) and WD40. It is not very much oil that gets in and causes the misfire, no more than probablly 1/8 cup. Just causes a minor interuption in the ecu harness connector. If it was just on the outer of the wire a fix would be relatively easy. All you need to do is disconnect the engine harness connector from the injector harness connector (round barrel type connector) and if there is oil ingress you will see signs of oil begining here. If you see this it is time to do something and not wait until it gets to the ECU. The connector is located just below the rocker cover front drivers side of motor under the acoustic cover.

Originally Posted by rover

Omaroo

Checked out on the weekend.

Firstly, no sign of any oil on or around ECU plug, nor any signs in bottom of compartment well.

Actually, not sure what your harness looks like - but on mine, the harness enters about the same level as the ECU, but individual wires are separated from the grommet/bulhead seal and dip 50mm downward before entering the plug. One would think if any oil made it this far, it would drip into the compartment floor.

I did not check under the acoustic cover as yet.

Cheers

Rover

Excellent news Rover.... and thanks for doing that. I think that if I replace the current harness I have, Land Rover will give me one off the shelf that should be new type like yours with ther better seals. Very cool.

Cheers
Chris