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MG MGF Technical - 2002 MG TF 160 electronics

I have a 2002 MG TF 160 and I seem to have caused the electronics to refuse start the engine.

It started with a blown fuse 8 (side/tail lights LH, number plate lights, interior illumination, glove box light). Changing the fuse brought back all the expected items, but I decided to investigate the cause and at the same time fix my blower fan coils. I have looked for insulation damaged by the sharps bits behind the radio and also the wiring in the boot. I've not found anything obvious.

I confess that I did this all without disconnecting the battery (unwise I know).

I've also checked all fuses in the driver-side fuse box with a multimeter and the fuses under the bonnet are all fine.

So I removed the centre console and illuminated centre console side panels without breakage plus the glove box.

The renewed blower fan coils went in without problem and all 3 fan speeds now work. I reconnected everything except for the glove box light but have left all the removed panels unfitted.

I have tested that everything you can switch on does work so lights, indicators, windows, electric mirror etc all work.

The problem is the car now refuses to do anything on ignition switch position III (turn the engine). I get a glowing oil temperature light, a small negative deflection on the oil temp gauge and no sounds whatsoever. I've tried with the lights on to see if I get a dimming showing that current is being pulled for the started, but the lights remain bright.

The key fob locks and unlocks as expected and I've tried the four-times lock and unlock sequence.

So I'd be grateful of any suggestions.

One thing I suspect (but I could be wrong) is that the cables to the oil temperature gauge and the clock were under a lot of tension, as I wrestled the centre console off. I've taken off most of the insulation tape for the oil temperature gauge and the clock cable bundles, but can't find any snapped cables. However the oil temperature light comes on when I try to start the car, so could this mean I've broken a connection to the oil temp gauge (and also the ECU)? The plug connector into the oil temp gauge looks fine, with no pins pulled out from the back, but I haven't tested it with a meter.

I can send some pictures if useful.

Best regards,

Daniel
Daniel

It is possible that the non starting is completely unrelated or maybe caused by battery voltage drop. Do you have decent battery voltage? Can you monitor the voltage when you turn the key and see the relay cause a slight drop (about 0.2V IIRC)?
Given those symptoms I would look at the spade terminal on the starter motor - you can get to it through the boot grille. It lives in a harsh environment and can go open circuit at the most inconvenient moments. As a really quick costs-nothing fix try wiggling the connector to displace any high resistance corrosion that may have built up there over the years.
If that 'fixes' it, then you should revisit both bits of the connection for a thorough clean up.
C R B Simeon

Thanks C R B Simeon,

I haven't checked the starter motor wiring yet, but I did recharge the battery (made no difference) and checked also the single 80A fuse on the engine. So now every fuse on the car has been tested with a meter.

In the engine bay I could hear a very quiet but high pitched tone like a capacitor being charged in a flashgun. I hear this with no key in the ignition. So I'm not sure if that is a symptom of the failure.

But also as you helpfully suggest, I will look at the spade terminal on the starter motor.
Daniel Trangmar

One thing I didn't mention is that when the ignition key is turned, I don't even hear a click from the starter solenoid. The only reaction is the illumination of the oil temperature light. But I will be checking the starter wiring today.
Daniel Trangmar

If you can poke the red meter probe up the lucar connector on the wire to the starter motor and earth the black probe on the engine somewhere; do you see 12V when you turn the ignition key?
If not then the ignition switch or engine grounding may be the problem.
If yes and on re connecting it there is still no difference when you turn the key there are two options.
1. check that the main 12V supply to the starter motor - big diameter wire with a nut securing it has good 12V. If it does you can use a screwdriver to short it against the spade terminal which should engage the starter motor. The main supply is permanently live. This is a bit hairy in a confined space but you understand the test principle :o)
2. If 1. doesn't spin the motor you will probably need to remove the starter motor - which is no fun at all. Just before you do that; try hitting it with a metal rod to maybe jar the brushes into making contact.
Years ago this tapping of the starter motor (with an umbrella because it was raining) was reported to have saved more than one F breakdown callout!
Good Luck!
C R B Simeon

C R B Simeon,

Thanks for your suggestions.

I've done what I can in the confined space so here's what I've found today.

1. There is +ve 12v supply to the 80A fuse in the engine compartment verified with a 12v bulb on a lead to negative earth.
2. There is +ve 12v supply to the solenoid in the engine compartment also verified with a 12v bulb on a lead to negative earth.
3. I've wiggled the connectors to the starter and solenoid and none appear significantly corroded.
4. I wasn't able to pull off the lucar connector from the solenoid so haven't yet been able to test for 12v on ignition key twist.
5. Suspecting the earthing of the engine from perhaps a corroded engine earth strap (I couldn't see it) I tried a supplemental earth by using jump leads - one end to an earth point and the other to a gearbox case bolt.
6. I've also had some advice to look at the ignition switch. I took off the ignition switch cover and unplugged, examined and re-plugged the ignition switch connections. I didn't notice a loom behind the switch, but it's a 2002 so might be early enough to have what appears to be an early problematic switch.
6. I have no power to the glove compartment light. All fuses are in order and everything else on that circuit works, but I wonder if a short here caused the fuse 8 failure which is why I started the dismantling and seemed to have caused the non-starting.

So I am still getting total silence when twisting the ignition key (no relay or solenoid noise) and an illuminating high oil temperature light. Do you perhaps know if there is a relay that drives the solenoid power or is there a direct connection from the ignition switch to the ignition solenoid?

Best regards,

Daniel
Daniel Trangmar

I am sure it is a direct connection to the starter solenoid from the ignition switch. If you can get the lucar connector off, it is relatively easy to short the permanent +ve to the lucar spade in situ using a screwdriver. If the motor doesn't then spin, you probably have worn or seized brushes.
Your test in point 5 above is not conclusive as the whole engine and gearbox is rubber mounted - hence the engine earth strap. A better earth would be to the chassis or body if you can find a clean enough bit. Also jump leads can be surprisingly poor conductors even on battery terminals!
C R B Simeon

C R B Simeon,

Again thank you very much for your suggestions and I managed to pull off the lucar connector and shorted the connections with the starter springing into life. I then tested for a voltage to the lucar connector when twisting the ignition key. No voltage.

Then with some assistance in looking at the circuit diagrams and thinking again about the fuses, we identified an anomaly in the owner's handbook which seems to have been the route cause.

But the good news is the problem is now solved!

Here's the issue and others may be similarly misinformed by the owner's handbook.

My owner's handbook on page 104 shows the main fuse box specification with a satellite fuse box on the right of the main driver's side fusebox. The lowest fuse is shown as F24 Heater Blower. This fuse I borrowed to replace a blown F8 for my initial investigations. I thought this was a good idea as the heater blower is a standalone non-critical component.

But today I also found some more fuses so added a fuse to F24.

Then the car started as normal!

The reason is that the F24 position shown in the handbook is not actually heater blower - it looks like it should be F19 Engine Management. And it is shown on the fuse box door chart as START.

So the moral of the story is a) to be guided by the fuse charts in the car not the handbook and b) don't try to trace any electrical problems without having each and every fuse in place.
Daniel Trangmar

Good result, but how frustrating. Your explanation may help someone else down the line - thanks!
C R B Simeon

The START fuse usually means it's in the switched live from the ignition/starter switch to the sarter relay.


No wonder it wouldn't crank!



Still at least you sorted it out.
SR Smith 1

This thread was discussed between 13/04/2015 and 31/05/2015

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