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MG MGF Technical - Immobiliser (was: Plugs not firing after new clut)

I've had an autoelectrician look at the car for 4 hours today and has told me that my plugs aren't firing as there's no voltage to the ignition coil.

He had all the wiring specs for the car and apparently the feed to the coil doesn't go through the MEMS so that's not the problem. He suspescts that the immobiliser may be causing the problem due to the battery having been disconnected from the car for about about 12hrs for a recharge. Prior to this the battery had run flat and didn't even have enough power to open the doors from the keyfob, so the immobilisers probably been without power for longer than the 12hrs.

I read somewhere that activating/de-activating the immobiliser 4 times will cause it to reset. Although the locks seem to click for about a second after doing it still doesnt fix the problem.

Does anyone out there know if this is the correct way to reset the immobiliser or has anybody had their battery off for an extended period to confirm/deny this theory?
Ross

Have you tried the manual method of using the Key code. This can be used to switch off the immobiliser when the fob battery goes flat. You should have been supplied a card with the car documentation with a four digit code on it. Use the instructions in the manual to reset the immobiliser, if it doesn't work the horn will sound. There has been occasions when the codes are incorrect, if this occurs increase digit 2 and 4 by one number and try again.

Chris

Also you could try resynchronising the Key fob blipper. With the key fob battery removed press and hold each button in turn for at least 5 seconds. Refit the battery (+ side up) and re-assemble handset. Unlock the car using the key, then operate the handset lock button at least 4 times to re-synchronise the handset.

If this fails complete procedure again.

With the car unlocked hold the handset close to the car, and operate either button at least 4 times (or until the door locks operate in quick succession)

Chris

Haven't got the keycode i'm afraid.

That'll teach me not to buy an import...

So when the blipper is activated 4 times that simply re-synchronises the blipper, not an immobiliser reset as i'd read elsewhere?

The blipper's working fine at locking and unlocking the doors, i thought maybe the immobiliser had locked up after the battery died (thinking someone was tampering and trying to nick the car) and has decided to stay that way even though i've blipped the doors open.

blip blip blip.
Ross

Ross,

The method I described resyncs the blipper to the immobiliser.

An MG dealer can run a diagnostic check on the Vehicle to gain the immobilser access code. Cost's about 25 I think, with proof of ownership of course.

Then you could use the key code technique but I am concerned now that if the blipper is synched and not operating the immobiliser then the problem may lie elsewhere.

Bruce Caldwell or Dieter may be able to shed some more light, once they read this thread.
Chris

Ross,

Have you checked that the inertia switch was not disturbed when the new clutch was put in? The switch interrupts the supply to the main relay in the MEMS Relay module. This relay supplies the coils, control valves and stepper motor.

Bruce
Bruce Caldwell

PS The Inertia Switch is on the LH side of the engine compartment near the MEMS. A rubber button on the top resets it.

Bruce
Bruce Caldwell

PPS Oooops!

Talking out of the small hole at the rear.....

The inertia switch doesn't supply the coils etc (only the fuel pump) but check there is a live feed from the MEMS Main Relay to the Brown / Pink wire on the Purge Valve. The MEMS relay supplies the coils, injectors and if it isn't operating then the engine won't start.

Bruce
Bruce Caldwell

A bit more info that I forgot to mention that may help...

Although the starter motors turning there isn't any petrol smell, even after repeated attempts at starting. And we've removed one of the plugs to check for sparks so surely there should be quite a strong smell.

Also whilst re-covering the engine compartment last night in preparation for 'giving up and towing her to the garage' we found a loose cable and connector between the engine bay cover and the soundproofing (passenger side). I couldn't find anywhere this may plug in so I'm assuming its a supply for a heated rear windscreen. Also this lead wouldn't have been disturbed until we removed the engine bay to find why it wasn't starting so isn't really a likely suspect.

I'll check the inertia switch and supply from the MEMS today.

Thanks for the help

Ross
Ross

The cable you found loose is, as you assumed, probably the Heated screen connector.
Chris

Another thought. Check Fuse No 2 under the front bonnet. This fuse supplies the MEMS relay.

Bruce
Bruce Caldwell

Already checked the front bonnet fuses and they're all okay. I'm gonna check fuse 14 in the passenger compartment fuse box tommorow as dieters site shows that this also supplies the MEMs.

Haven't had a chance to check anything today as I've been working, as has the mechanic whose garage the car is currently occupying.
Ross

import or not, your local friendly Rover dealer can look up the key access code on the database and tell you. Mine did not charge as it only takes 2 mins...
David

Ross
<<has told me that my plugs aren't firing as there's no voltage to the ignition coil>>

Aah! I've just noticed that you said coil singular so I presume your car is an MPI. Therefore Fuse No 14 under the dash supplies the coil unlike the VVC where the Fuse No 2 under the bonnet feeds the coils. Sorry for mis-information. Fuse No 14 is fed from Fusible Link No1 under the bonnet which I presume is OK or you would have no lights! Fuse No 14 also feeds the Alarm ECU.

Let us know what the diagnosis is please.

Bruce
Bruce Caldwell

Had a quick check:-

Fuse 14 is fine, and resetting (what i think is) the inertia switch hasn't changed anything. There's a load of cabling running very tightly over the top of the reset with almost no slack so it was hard to press the switch. is this the correct switch? clipped to the inside of the left rear wing?

I'm looking less and less forward to taking it into the garage on monday as I get the feeling they're going to have just as much trouble as we are finding the fault and charge me handsomely for the privelege...

I asked advice from atpelectronics.co.uk and a nice chap by the name of Richard was kind enough to send the following reply

------------
When this unit is immobiliser active it will still spark but has no switching to the injectors.
This means this is not your problem. If there is no spark then it sounds like there is a trigger problem
this usually means that the person fitting the clutch has damaged the teeth on the flywheel which trigger the RPM sensor or the flywheel is replaced with the wrong one when the clutch is out.
The only suggestion of it being the ECU is if perhaps the battery leads were sparked when refitting the battery but check the above first.
------------

So... My next question would be how do I check the flywheel?
Ross

Ross

I don't have an MGF but I am building a GTM Spyder and using a VVC motor. Previously had a lot of trouble with starting. After a lot of mucking about (research!) I found that the battery voltage is crucial to starting on this motor. If you are standing voltage is less than 12.4 volts the cranking of the starting motor will drop this voltage to about 10. At this voltage you have a very poor spark and your injectors don't work. I don't know if this applies to the MPI but feel it is probably worth doing a study of your battery voltage while trying to start. For this you will require a good digital meter.

With a fully charged battery my motor starts first time every time. Hope the above is of some value.

Regards

Alex
Alex

Difficult to check the signal from the crankshaft sensor without the use of a Testbook. This means a visit to an MGR garage.
You could check the sensor for damage by removing it and checking the surface of the probe. The operation of the sensor depends upon the correct distance between the sensor and the flywheel. Check that the sensor has not been bashed by the person fitting the clutch. The sensor is down on the bell housing/engine adapter plate on the LH side as you look down from the boot. You will have to remove the engine access cover (the parcel shelf) to get to it easily. There is a two wire angled connector on the sensor and the sensor is secured to the bell housing by one bolt. The sensor provides the signal for the ignition and the injectors.

Bruce
Bruce Caldwell

Car now in the hands of my local Caffyns MG Rover dealer.

When the chap in the service reception looked up the cars history on his computer it shows that the car had a new MEMs, relay, distributor, rotor arm, etc, last Feb and apparently has a record of poor starting (until now it's been fine in the 5 months i've had it). Apparently the only part of the ignition system that wasn't replaced was the crankshaft sensor.

Anyway, hopefully it won't be too expensive to put right. Also I'm kind of assuming that as this work was all done less than a year ago (at the next caffyns down the round...) it should still be under warranty??
Ross

PS. Thanks to everyone for their suggestions and thoughts on this.

Although I haven't managed to fix the problem myself I have learnt a lot about the car in the last week whilst attempting to find a cure. (just can't wait to get it back now and hear the newly fitted K&N).
Ross

This thread was discussed between 29/01/2003 and 03/02/2003

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