V6 Automatic not starting - immobiliser?
 

Last November, my Dad's 75 tourer V6 auto failed to start. Out came the RAC who diagnosed an immobiliser fault. He had it towed over to me and it's sat on the drive ever since.

I've finally got around to investigating it, popped a known good battery in, but no joy.

It doesn't even try to start. Dash lights up normally with the ignition on, but absolutely nothing happens when I go to start it.



No error codes on my cheapo code reader.

I whipped the air box out and cleaned the spade connector on the starter motor, no joy.

Because absolutely nothing happens when you go to start it I suspect it's not even getting as far as the starter motor, so the original diagnosis of an immobiliser problem might be correct.

I whipped out the immobiliser unit and there are signs of corrosion on the board.
https://i.ibb.co/LSktBnq/20190221-102115.jpg



https://ibb.co/yWvNzCh

Does anyone please have any clues as to next steps?

Haven't changed keys recently have you?:shrug:

Thanks, nope, still the same two keys. I opened them up just to double check the little chip thingy was still in place.

Stupid question, but sometimes the obvious things are worth eliminating.

The car isn’t in gear when you try to start it, is it? Needs to be in Park.

No such thing as stupid questions! That was the first question I asked my dad when he rang up and said he couldn't start it :D

It's definitely in Park. Tried it in neutral too. The display on the dash shows the right gear ("P" or "N") so presumably the car "knows" which gear it's in so it's not a problem with the selector (?).

I would run a wire direct from the battery to the spade on the starter solenoid. if this turns the motor you can eliminate the starter and solenoid as the problem. ( Car in park of course).
That said the immobiliser looks suspicious

Yes, post me the immobiliser and I'll sort it out for you ;)

This car presumably has a sunroof, and if you turn over the PCB on the opposite side to where it is corroded, there is a 1/4w resistor under the black relay, and to the right of that a couple of transistors which will have bought the farm.

Brian :D

Good idea. I ran a wire from the battery to the starter motor and it fired up, so the starter motor is fine.

Great stuff. No sunroof, but I think you're right that the immobiliser is goosed.



https://i.ibb.co/xh07NQ7/20190224-113306.jpg



I'll drop you a PM Brian. :bowdown:

This is not the first time this EWS has been "repaired", loads of conformal coating removed from the PCB, snots of solder here and there, and inside the connector housing is evidence of green gunk having been cleaned off in the past.

Notwithstanding, I've condemned it........replacement winging it's way back tomorrow along with the duff one :cool:

I suggest looking to see where the water is coming in, normally when they're as bad as this one, the car has a detached sunroof drain.........but no sunroof on this car :shrug:

Oh and a smear of Vaseline on the female contacts of the EWS plug before you refit it Gary ;)

Brian :D