Hi Phil
Yes, as Andy explained there have been isolated issues with an item called the 'Combined Relay' (some call it the Mulifunction Relay if your looking for parts) which is part of the GEMS system, its used to energies both the ignition and fuel injector systems. The problem occurs when you switch off the cars ignition, the Combined Relay is supposed to cut supply to the ignition and fuel system and it doesn't, it stays energised (Live).
Hope this is not teaching you to suck eggs but the item your looking for on a UK car is on the bulkhead top, alongside the heater box on the passenger side. Its black plastic and about half the size of a VHS cassette (that's a very crude guide, its been nearly 20 years!).
You will see a few wires entering its base. Now to confirm you have the correct component ask someone to turn on the ignition whilst you have your hand on it, you will feel it click and in a quiet garage you will hear the click. Turn off the ignition and after about 10-20 seconds it will (or rather should) click again as it switches off. The delay is down to the system gathering base settings for things such as the IACV (idle air control valve)... none of that is important now.
OK, you now need to find the output supply to the fuel system (Injector feed), for the life of me I cant recall the wire colour but with a simple 12v test lamp look for the wire that the test lamp is OFF with the ignition off (and the relay has clicked to shut it down) but goes live when you turn the ignition on AND then goes off again after you turn off the ignition and the relay clicks. Sounds complex I am sure but its not if you take it in stages.
This is the wire you need to break into for the warning light feed, I used a spare alarm LED (be aware they have a polarity so only work one way round) and simply wire it in somewhere out of your eye line so it doesn't distract you but you can visually check after you turn off the cars ignition, it should stay lit as I say for about 10-20 seconds then switch off.
This was just about the only issue I had with GEMS and maybe nothing to do with the GEMS itself as it only started after I had the car chipped so could be a fitting issue with the chip set or a software glitch. That car is still running fine today with its current owner and my crude work around is still working perfectly nearly 20 years later.
The real expert on GEMS was a chap called David Ashley-Pool who worked out the whole system and he came up with a much better fix using a small relay to supply the Combined Relay but I had already fitted my warning light by then, David saw my work on a trip when he came to stay with us and laughed his head off, typical bloody mechanic was his comment..... David was a Top of the tree test pilot on Harriers and other fast jets..... Top guy!
Hope that helps
BR
Colin
