S500 W140 immobiliser issue

[General patten]

It could be the ignition switch?

Would that stop central locking opening on ir key fob

 

[General patten]

Well the car is SORTED now.....the problem was the PSE pump"central locking"..I pulled out fuse 9 waited 30sec put fuse back in and opened door on remote and it worked,car started first time..

 

[Mitsub]

Hi
I'm new to this forum and wish to seek help with my S500 W140.
Its registered Aug 1993 and according to previous owner she served in the UK Qatar embassy. She's been sat outside unused for about 10yr. It was a dud fuel pump. Don't understand the logic of having 2 pumps in series. The dead one prevented the still working one from getting fuel out to the engine. I replumbed to the working pump and got her running. The ride is sublime and she ran ok. Then I played with the infrared key whilst sat inside and pressed the central locking button on the console. The immobiliser suddenly kicked in and shes been immobilised. It's been immobolised for 3weeks now. I've had her battery disconnected for days, ran a lightbulb across her battery leads without battery for days (to try drain computer internal charge), tried the resync procedure as per owner handbook, but she won't crank over. The blinkers flash and the horn blares. Each time upon reconnecting battery and entering the car, either via IR door entry or ignition on, the immobiliser kicks in. No crank.
Ive tried looking for a K40 relay in engine bay but no luck. Of those relays I had a oom all the soldered joints look as good as new. The realys also look spanking and no sign of corrosion that could make them seize. Looked behind passenger footwell steel plate and no luck, although I've spotted a red/yellow wire I can't find a black/purple one, nor a small box these wires go in and out of.
I so wish to defeat this immobiliser as it's such a pain. Any ideas please?

i have got the same problem with my w140 s280 1996.in my case problem is in door handle.if i start moving door handle as i am trying open the door it suddenly yellow light flash and everything is back working again

 

[Mitsub]

i have got the same problem with my w140 s280 1996.in my case problem is in door handle.if i start moving door handle as i am trying open the door it suddenly yellow light flash and everything is back working again

48 hours later and scrap man would collect my merc.it was all set.and now i did cancel scrap man and i am going to keep it