injector stuck open

Help
Ive seam to have injector number 5 next to the airbox stuck open, i e swapped out with different injectors in that slot but they all seam to do the same. Cable looks ok and injectos off my other coupe good and working

If i remove the connector wire it stops jetting constantly, reconnect turn the ignition to prime the injector then opens fully. Something is sending a signal to open fully

Any ideals why ??

The only thing that can drive the injector is the output transistor in the ECU. Sounds as if it's failed short circuit.

Replaceable, if you're good with a solder station and can get the part, but probably easier to change the ECU for a virginised one that can learn your immobiliser.

It could also be a short in the wiring to that injector.

The injectors are supplied a constant +12v and are switched to ground via the transistor in the ECU, so if that wire has rubbed through and is touching the chassis somewhere it would constantly open the injector.

Disconnect the ECU plug and test the pins in that injector socket, if one is grounded then that's the problem and you have a short on the wire somewhere. If there's no short to ground on either pin then most likely the transistor in the ECU has failed.

With the ECU plugged in and ignition on the other pin should be at +12v, just to confirm you have the right one.

Oh yeah, I forgot they were ground-side switches.

The loom that feeds the injectors is a short length from the connector bundle behind the battery; everything else is in the main bundle through the bulkhead and will be a complete pain to find a short in

If you're lucky the short will just be under the cover on top of the fuel rail, the heat there does cause the insulation to deteriorate.

I can solder but dont know which part to replace. Who would be placed specialist to this ?
I will check the wires again though

Thanks for all the help so far !