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It seems you replied whilst I was typing this.

That 8 way engine bay plug does not seem to be present on the 200TDI vehicle that I have here.



I have also come to the conclusion that this is an oil pressure related inhibitor circuit.


It is clearly switched by the oil light (lack of oil pressure). White (Ignition live) and White / brown (oil pressure switch) across the coil (pins 85 - 86)


The diagram shows, White / purple (87a) and live (white pin 30) are always connected IF the oil light is off  providing power to White/purple (coil or fuel pump)

If the engine is not running the oil light will be on, and pin 30 (white / purple) will now be connected to pin 87 (white / red) ignition crank circuit, thus allowing the engine to crank / start with no oil pressure.

However if the oil pressure light is still on once the engine has started, there will be no power to White / purple (pin 30, pump - coil) when the ignition switch returns to its normal (non cranking) on position.

This means that if the oil light is on, the only time the white / purple wire (coil - pump) gets power is when the engine is cranked, allowing the engine to start.

So it seems that this circuit cuts power to the (coil or pump) if the oil light comes on when the engine is running, effectively stopping the engine.


Not quite preventing the engine from cranking with no oil pressure, but certainly stopping it from driving.


It seems looks like Land Rover built some vehicles for either people who were notoriously bad at checking the engine oil level, or perhaps for people who smacked hole in the sump for a pass time?


You could use the white / purple to power the fuel cut solenoid on the FIP and keep the feature on a diesel I guess.






Edited by MR-HIPPO
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1 hour ago, daveturnbull said:

I popped over to see my local friendly specialist at lunch time, and have a raid of his wiring graveyard for some relay holders. I also had a look at his big book of land rover looms and discussed what this relay is all about. 

White / purple does indeed seem to be related to the fuel pump and / or coil power feed on petrol models. His explanation was that it cuts the power to the spark / fuel circuit whilst cranking AND the oil pressure light is on, thus preventing the engine from being started until the oil pressure light goes out. Seems to make sense, even if the supply / load are wired in backwards to my mind.

So it looks like my loom was from a 200tdi era petrol model. My question now is, does a non-petrol loom of this age have a white / purple wire at the multiplug? And if not, does the oil pressure warning light wire (white/brown) just go straight from the multiplug to the warning light panel? I'm considering stripping the circuit out if it's not required.

All 90 & 110 pre defender wiring looms are common & have petrol & diesel engine connectors, my 1989 110 certainly does (rubber cased connectors) 

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