Driving to work yesterday my GTM cut out at a crossroads, assuming I'd stalled it I went to re-start, but it wouldn't turn over. I turned the car off for about 5 mins and tried again, the fuel pump didn't prime (normally does so quite vocally on "ignition on" position) and when I tried to start the car wouldn't turn over and the sections of the dash that use the switched 12v supply dies. RAC came to the rescue but after about an hour of fiddling he came to the same conclusion that I had - that either the ECU or immobiliser has stopped working.
Doing some research it appears the immobilizer only cuts the spark and the pump should work as normal, is this correct or am I looking at mgf stuff that doesn't apply?

Being rescued...
Immobilizer interface - I don't have a fob but this apparently talks to the ECU to deactivate it?...
Immobilizer (I think?)
ECU - wedge type (VVC 160 engine) - what's the back box that attaches to it?

Has anyone got any suggestions before I go and try fitting a new ECU/Immobilizer combo only to find that doesn't fix it.

Any help or crazy suggestions greatly appreciated or a prod to a different forum that can help if not...

hi i could be completely wrong here


the black box has 4 relays in it they are for the fuel pump / oxygen sensor / main relay / starter relay


just somting to cheek do you still have the Inertia Shut Off Switch - Fuel Pump like the one here
http://www.rimmerbros.co.uk/Item--i-WQT ... oCIAXw_wcB
i have heard this can pop open and stop the engine

i think this is right If its a 3as alarm type, ( single button fob), then
its only immobilised on the starter signal, it looks like you have the 3as alarm type in the photo but you have a mems3 ECU - wedge type (VVC 160 engine) - wich needs the later 5as type, (2 button fob), and matched alarm and fob. the 5as sends a signal to the mems3 ecu
you don't have a 5as alarm so your Immobilizer interface must talk to the ECU to deactivate it?...
or you have a un-coded ECU


hope this helps

So a quick update...

Went up the road to a local rover/mg specialist who reckons the ECU is fried and looking at the wiring I'm not entirely surprised, it seems when splicing in the MGF engine loom a fair amount of cables have been cut and either left bare or had masking tape put round them to end them. Also about 40-50% of the wires go nowhere which confuses the situation even more!

So I'm going to get a new metro loom and mgf engine loom and re build the wiring from the ground up.

How hard can it be....

Paul could be on to something with the inertia switch - they cut the supply to the fuel pump. The 5AS immobiliser also cuts the fuel pump supply but IIRC only after it starts i.e. it spins (you hear the whirr and then stops when it gets up to pressure before starting) but then it doesn't come back on after starting without the ECU handshake. It cuts the earth to the fuel pump though so you can get around that by simply running the earth for the fuel pump straight to a convenient earth rather than via the 5AS - less protection but less to go wrong!

I'm pretty sure the mems 3 should need the 5AS but your pic seems to show the 3AS so maybe the first interface box is a get around for that???

I'd check your various earths etc (and the inertia switch) before changing immobilsers etc. Also check over the wiring loom generally for any dodgy connection or short. I had a couple wires touching eachother that didn't pop any fuses but did lots of weird stuff like cranking the starter if you switched the hazzard flashers on!!!!

My Libra had the black relay box replaced shortly before i bought it. The old one came with the other spares i got with the car. Apparently its quite a well known failure according to Rover forums.
I had a similar problem to you last year. I thought it might be a fried ECU. But decided to try replacing the relay box again as it was much cheaper than the ECU. Turned out to be neither - it was a poor connection in amonst the spagetti that passes for wiring in the engine compartment. Took a while to sort but now i have slightly less spagetti.......
But i'd check the relay box as its a known problem.

it cant be that hard i did

I got a MGF loom from ebay for a mems 3 ecu and cut the part out that was for the engine and the instrument cluster most of the wire is the same for the metro
there was not much left of the mgf loom photo 2 with instrument cluster

if you do get the relay box there are to different types

ENGINE MANAGEMENT RELAY

YWB100970

and i think this one is for the

air conditioning

YWB100801

they look the identical

Paul is right, I spent two days trying to start the car with an air con relay, DOH!

Wow - thanks for all those suggestions! I've tried every component, bypassed the inertia switch and measured the voltage/resistance down each wire, with results that dont even resemble what they should, not helped by some of the wires changing colour 4 times as they travel down the car!

Should have the majority of a full MGF loom to play with and have a full low mileage metro loom too. Plan is to lay it out on the floor and remove most of the redundant wiring as my current loom has 15 plugs under the dash which are attached to nothing!

I had a similar problem which turned out to be a rusted relay leg inside the separate black box, you can lever the unit open with a knife or screwdriver. A small soldered bypass did the trick.

All relay boxes have been checked and the more I look at the wiring on the car the more I just want to rip it all out and start again, I've found more examples of wires twisted together with tape around them, 10-12 pin connector blocks being used to connect a couple of wires, 3, yes 3, different radio connectors under the dash.

Got a newish looking metro loom, a VVC 160 engine loom and my ecu had now had it's immobilizer deactivated properly so I can wire the engine and its ancillary's in as simply as possible.

The job starts on Monday - I have a feeling I'm going to be asking a fair few questions on here!

Good luck with that - you'll probably save a few kg of weight along the way too!

I hope it all go as well as my one did,
i changed it from a 1.6 to a 1.8 vvc mems 3 it seems to work on my car

if this is any help, this is what i did

I got a full mgf mems3 car loom the engine i got had the mems3 engine loom on it




I was going to use the mgf electronic speedo so I got a set of new MGF Gauges.
changed from the cable speedo
I cut down the full loom to just to what was needed to run the engine and the new gauges and labelled all the wires.
i found that most of the wires you need was in the plug which come from the metro loom for the engine (this is the plug that gtm extended )
all the cars lights were done with the metro loom



I did find that the mgf had this under bonnet fuse box witch was a bit big and it was at the front of the car this was for the live feeds for the.
Engine management relay module /Engine management relay module, inertia switch /ECM, Multi-function ECU /and many more
so i changed it for one i got from ebay.



the new fuse box gets a live feed from the main battrey cable wich comes from the battrey to the starter motor so i did not have to run 4 live feeds from the front of the car.
the 3 brown wires one of them was joined in the mgf loom.
I cant remember which one it was. the fuse box I got had 4 fuse so I put the 3 brown wire,s in it and one purple and brown.
i think was for the ENGINE MANAGEMENT i will have to find this out and one day label them up





there was some more wires from the mgf loom for things like/ DBO2 socket /ALARM / ENGINE TEMP / ENGINE BAY FAN /

i do not no if any of this is any help to you
good luck hope it all works

It runs! I've also got pretty much all the electrical systems working with only a small problem with the indicators/hazards to fix (Neither works, but if you turn the hazard button on, then the indicators work )

Photos to follow...

That sounds like you are pretty close. Just stick a BMW badge on it and you won't need the indicators to be working