Engine and Transmission Tech

Hi Guys,

I am a newbie here form Johannesburg, South Africa, and the owner of a Land Rover Discovery 3.9 V8 with the 14CUX system. A problem has developed after the vehicle stood for about 8 months in that it is over fuelling like mad, so bad that it is diluting the oil and throwing petrol out the exhaust. I have had the injectors tested and cleaned and they are good. I have tried to change the ECU, no difference. The diagnostics read correctly on the temperature, when the engine has been running for a while, the temperature reads 82 degrees C, so that points to the sensor reading correctly and not holding the injectors open (or so I would assume). The injector pulse however is running at about 7ms at idle and should be about 2.2ms. Has anyone any idea what would cause the pulse to be so high. I have also changed the air flow meter, stepper motor and throttle position sensor from a vehicle that works, no luck, the pulse timing stays at 7+ms. There are no oxygen sensors on this vehicle.

Has anyone had a similar problem to this?

Fuel pressure too high? Bad regulator?

There is a "tune resistor" used for the 14CUX that tunes the pulse on some vehicles but not all. Most 3.9L had them either NAS or ROW. On Defenders they're usually inside the vehicle under the carpet along the transmission tunnel. The location on a Disco is somewhere near the relays. Here is a quote off RPI's website, "A Green tune resistor (green referring to the color of the wires) will always give a non-cat tune, and White is always a cat tune. By the way, the default (Limp Home) tune is a cat map, so this usually makes a non-cat car run very rich." There is also a fuel temperature sensor on the fuel rail that clears air bubbles when hot to prevent vapor lock. I don't have the electrical specs to test. It's purpose is to hold the injectors open to clear the bubbles meaning the pulse would be lengthened.

Those are the two area I'd be giving a look at.