Thread: This is a weird one, Earthing issue..?

The housing on my 14cux is earthed now - it is in the same spot as yours, and screwed to a metal bracket that is screwed to an earthed part of the car, however, while I was testing the new engine, I had the ECYU sitting on the floor - on a bit of carpet, so not earthed then and it still worked fine.

That is one odd fault - have you checked the main earth from the chassis to the engine - that needs to be spot on as all the sensors are earthed through that.

Cheers - Gav.

switches usually work on the positive wire (negative earth) and the light or whatever has an earth lead to somewhere nearby. so earthing the switch is just creating a short i would have thought.

The door light switches are a ground switch - one wire that is earthed when the door is opened. The lamp has a constant 12 volt positive on it, so this earth completes the circuit and lights the lamp. The fact that it causes the engine to play up suggests a dodgey earth somewhere.

That's what I thought,
I'll out the engine earths first and see what happens

Cheers nAT

Sorry, I should reread what I type, my brain goes faster than my fingers. I'll check out all the engine earths first. Then I am going to remount the ECu, theres a single screw holding onto the steering column.

Does anyone know where the ECU wires earth to?

Cheers nAT

Pins 14, 27 & 40 need to be grounded. See the document below - I used this when I wired mine recently and it runs, so it must be right...

Rover 14CUX Hot Wire Mass Flow EFI: Service and Troubleshooting

Cheers - Gav

This might sound silly but... if touching that wire to metal makes the engine play up and grounding the ECU doesn't help. I'd be wondering if you are loading up the circuit on the ignition coil feed. It is a long shot but if you measured the voltage on the pos side of the coil with the ign on, then touched the wire from the interior light on the metal to see if the voltage drops across the coil and it does drop considerably it might have something to do with it.

Originally Posted by Jazzman

This might sound silly but... if touching that wire to metal makes the engine play up and grounding the ECU doesn't help. I'd be wondering if you are loading up the circuit on the ignition coil feed. It is a long shot but if you measured the voltage on the pos side of the coil with the ign on, then touched the wire from the interior light on the metal to see if the voltage drops across the coil and it does drop considerably it might have something to do with it.

Nice thought - I've seen stranger...