Topic

Hi all
I have a 98 year mgf mpi (non vvc) going round a traffic island it just cut out
Got towed home
Fuel is flowing but no spark immobilizer turns off , engine bay inertia button fine
Changed the crank sensor, still no spark from the coil
My main question, I see I have a few broken wires in the boot hinge loom . I have read the other topics here and reviewed dieters wiring diagrams but I am trying to figure out if any if those wires could interfere with the EMS switching the coil?
Their is a green/ purple wire that is cut and I can't see that on the wiring diagrams ?
A couple of earth's are also off but as far as I can tell these are all just lighting related ?
Or does one if them interact with security.

The engine turns over strongly, fuel all good just no spark at the coil ?
Thanks for any ideas

Cheers

A lot of security systems use interior and boot light switches to tell if the door/ boot/ bonnet is open

Hi and welcome to the forum

There is wiring info on here if you look under the community tab at the top of every page.

I think the wire you can't trace is purple with a green trace but I might be wrong.

The alarm wiring from the boot is to tell the 5AS ECU not to trigger the alarm if the boot is opened.
There is another wire that tells the system that the boot latch is open and it can be assumed that the boot is open.

There is no wiring in the boot loom that will stop the car running so I think that is a red herring but there is no harm in repairing them to prove me wrong.

If you have no spark I would be looking at the ignition system, especially as the mk1 MPi is coil and distributor so a fault can easily effect everything.

James

*under the community tab in the download section.....

Yes, thanks for the input.I think you are right.
I have been working through the ignition system, I had a crank sensor (known good) so tried that. Have ordered a coil although my tests suggest this is not the issue but they are cheap enough so am trying it to rule it out.
Was tracing wiring and checking continuity which was when I found those broken wires, but again, with the fuel pump running I doubt it is security system related.
My main concern now is that it is the MEMS but will swap out the coil first and HT leads just to be sure.

Then I guess I work through the MEMS connector with my multimeter, Joy of joys......

Thanks

My new HT lead set arrived today so I thought I would test a bit more after work.
I Put all the new leads on including coil to dizzy.
Still no spark so I put my multimeter across the HT lead from the coil and to an engine earth and even with the ignition off I have full battery voltage at the coil HT output
That sounds odd to me, does anyone know if that's right or does that mean the coil has failed and is shorted ?
Sorry, electrics not my strong point but it seems odd to have permanent full battery volts there ?

Thanks for any input .

Certainly possible for 12V on HT of coil

See diagram of typical coil construction.