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TD5 Injector loom replacement

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This is how to replace the injector wiring loom on a TD5 engine. Symptoms of wiring loom failure is a misfire (not a backfire), when accelerating. The problem is caused by engine oil contamination to the injector plugs inside the rocker cover, which are soaked with engine oil all the time the engine is running.

The oil will pass all the way along the wiring loom to the ECU and then drip out into the ECU/battery tray.

It's very simple to replace the loom - tools required are only an 8mm socket, philips screwdriver, a small pry bar/screwdriver for leverage, a 13mm and 10mm spanner or socket, a pair of pliers, and a can of brake cleaner or similar substance, and a smear of grease/Vaseline.

Battery cover off first - turn the lock screw 90-degrees, press the tab at the rear of the cover towards you, and the cover will come off.




Engine cover next - two 13mm head bolts on the passenger side, and one on the drivers. Lift the cover up at the front, then forwards and off the dipstick and oil filler.





With a pair of pliers or mole grips, compress the breather pipe fitting, disconnect the pipe and tuck it out of the way.


Clean around the rocker cover gasket joint and remove all the 8mm head bolts that hold the rocker cover to the engine.


The rocker cover will then lift away to expose the injector wiring loom/camshaft, etc.


Disconnect the earth terminal on the battery (terminal closest to the wing), and also the 2nd earth point by the ECU.



The injector wiring loom is plugged underneath the rocker shaft housing - squeeze the two locking tabs either side and pull the plug downwards.


Lever the socket out of the housing with a small pry bar or screwdriver - be careful not to damage the alloy housing.


Disconnect the 5 injector top plugs - squeeze the wire bar inwards and the plug will lift off.


The old wiring loom will then come away and the new one put in place. Connect each injector by pressing the plug down quite hard until it clicks in place. Work form the back to the front, apply a small amount of grease or vaseline to the two O-rings, and press it into place on the end of the housing. Keep it in place and connect the plug from underneath - again, it'll click when it's fully located.


The new wiring loom won't sit in the guide at the edge of the housing, so keep an eye on it when you refit the cover.


Clean the rocker housing gasket (or replace it). These gaskets are well known for leaking, so consider putting a very thin bead of RTV sealant on the old or new gasket before fitting it. The rocker cover bolts go through a restricted guide, so tighten them down until the bolt stops. Don't overdo it - the bolts are M5 and can shear or strip the thread.

ECU next. Release the rubber retainer for the jack and remove it, then undo the single philips screw that retains the ECU - lift and turn the ECU until it vlears the housing.



The red plug is where the engine oil ends up - squeeze the locking tab in and unplug it.



A can of brake and clutch cleaner is ideal for removing the oil, so blast the plug and socket with it and allow the cleaner to evaporate. Reconnect everything and then go for a drive. You may feel the engine hiccup a couple of times until the ECU realizes that everything is working fine, but otherwise - performance should be restored.

The remaining oil in the loom will continue to migrate to the ECU plug, so you may have to clean the plug a few times. Alternatively - you can nip a hole in the wiring shroud at it's lowest point and the remaining oil will drip out onto your posh drive :)


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