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MG MGF Technical - ECU - help please


Last time I have sent thread regarding melted igniotion coil. Today I was able to check my car using T4, erase all codes but problem has left.
I have checked new igniotion coils, sparks, LT cables and it looks that there is a fault either with ECU or cable with power which is connected to igniotion coil (cylinder 1,4).
Today I have started the engine and once car was working properly, sometimes cylinder 1 and 4 dont want to start so we put for a while ground to minus cable and the car was running as it should.

There was even situation that everything was working properly so I started to get back the car together. But for the last time I decided to fire a car once again and the problem has occured.

Can someone suggest me something? is it problem with cables and I should put new one or there is a fault in ECU and I need to replace it (it is going to cost lots of money .
Personally I think that it cannot be ECU because why sometimes it works and sometimes don't so I need to add extra ground to start other cylinders working.

help, please

did you see this web page?
I don't know if it can help you
i hope yes
see you

No idea.

Just a thought regarding electronics test made _by craftsman_.

@Will M.
... please forgive my ignorance

I've never seen a MK2 ECU from *inside*, but assume there's not much difference to the older regarding i.e. output drivers.

(Anyone should send me a broken, and I'll tell you) :)

The old was electronics with 1995 state of the art.
Intel Micro controller and big other parts together with huge power drivers (thyristors or what).
SMT assembly technics was in the _children shoes_ and unreliable solder joints where not uncommon.

Long speach...
I don't think there's much improved with the _newer_ MEMS3 ;-)
Some obsolete parts replaced and increased qty of outputs/inputs. The other _content_ is just software/firmware.

However, a temperature stress almost shows intermittent failures.

Apply heat with a heat blower to the ECU box and heat it up to 60..70 degrees.
See what it does then.
Stress to opposite lower temperatures should be no problem now in the east ;) That's for sure standard in these days.

Dieter K.

>> Today I have started the engine and once car was working properly, sometimes cylinder 1 and 4 dont want to start so we put for a while ground to minus cable and the car was running as it should. <<

This problem does sound electrical - so the questions are:
1. are both coils getting power?
2. are the HT leads powering up as they should?

Some simple diagnostic equipment should be able to tell you whether the problem is with the high tension (HT) or low tension (LT) circuits (a strobe light could be used for the HT side - or you could remove a spark plug and ground it to see whether there is a spark).

If a LT problem, then the fault could be followed back to the ECU - but check the easy and obvious first.

Good luck
Rob Bell

Thanks Rob,

Probably I have forgot to mention this fact you are talking about but the answer is Yes. We have checked both new ignition coils, cables LT, sparks and so on and everything is OK.

The problem is: sometimes no power in muliplug connector which is connected to igniotion coil (cylinder 1 and 4).
The car sometimes starts with 4 cylinders and everything so OK and sometimes I need to add (connect) ground to the plug and then everything is OK.

so the reason in my opinion could be:
1) fault ECU (repair would cost me about 300 GBP)
2) broken (fault) ground cable which goes from ECU to igniotion coil

yesterday evening I have examined Workshop Manual Electric Diagrams and found that PIN 26 and 52 is responsible for conection with igniotion coils.
Unfortunatelly I am not electrician so I cannot figure out what stand for the letters of color codes, nummbers and so on...

Maybe someone can riddle this out for me. (color of cable, length, thickness, is it directly connected or there is something betweeen)

Will is probably your man for explaining the electrics (certainly much better than I!) - but my understanding of the codes is pretty much the same as yours. If you take the example, LGS, 1.0 - this means that the wire is light green, with a slate grey tracer and the wire is 1.0mm2 thick.

For power distribution and earth, there may be a third number, for example LGS, 1.0, 150 - where the wire is the same as described as above, but is 150mm long between the connector and the first joint.

The key to the wire colour codes can be found on Dieter's website:

Hope this helps Marius :o)
Rob Bell

Wires for the coils are as follows:-

Brown/Pink is the live feed for the coils. It is connected to both coils.

White/Black is the other connection to each of the coils. One White/Black is connected to pin 25 on the ECU and the other White/Black is connected to pin 26 on the ECU.

If you have a fault which shows no live supply (12v+) connection on one of the coils then the Brown/Pink wire must be faulty.

The Brown/Pink feeds into one coil on pin 1 and then feeds out to the other coil on pin 2. It enters the other coil through its pin 1. The White/Blacks are connected to each of the pin 3s.

Determine which coil has the faulty supply and check the connection of the Brown/Pink wire.

Hope this is clear!

Bruce Caldwell

As far as I remeber there were two cables which go to plug which I connect to ignition coil. Anyway within 15 minutes I will go to workshop and we will be searching for a ground.

Hope that this is the reason not ECU.

Hi again,

Finally, I hope, good news for me. Yesterday evening I have directly connected additional (leaving old one) cable to ECU plug (pin 52, white orange cable) and at the other end to ignition coil plug. So far - yesterdays tests and today ride (20 miles) - everything is working as it should.

I have only doubt whether should I investigate this white orange cable or leave it with this additional one. Telling the truth I don't want to do that because there is a lot of work to do to get to group of cables (it looks that I have to dismantle throttle body and other parts).

what do you think?

Good news that the car is working again Marius - but I would still like to know why the problem occured in the first place: it could be something that is waiting to strike again when you least want it.
Rob Bell

You are right. it is interesting why this has happened. First place I go to the airport using airport transfers sevenoaks to practice driving in snow (finally snow has fallen in Poland) and latter this day I come back home and spend another night in garage.

This thread was discussed between 31/01/2005 and 02/02/2005

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