ECU repairs on W124 E320?

[Richard.Wilson]

Guys,
I had a misfire, intermittently moving from coil to coil, then a complete ignition failure on one coil. Chased the problem replacing a coil then all the leads and caps. It seemed that the wiring loom was breaking down (known fault), so sought advise here and elsewhere, and changed the loom.........total £600 later........The ignition failure on one coil is OK, but the intermittent misfire is still there.
It effects the front coil only, and does not appear to be related to any of the components. The spark stutters slightly when strobed at tickover, and stops completely as revs rise under any load. Then it comes back as the revs drop again.
Seems logical that it's probably the ECU, and have been advised by MB that it was probably damaged by a short circuit. If so, then it should have just damaged an output driver component on the board
Can anyone recommend a good ECU repairer?
or does anyone have experience of fixing them, who could advise me how feasible it is?
Any other thoughts before I condemn my ECU?
Regards
Richard

 

[jberks]

I have no personal experience, but it can't be that hard. I did fix a car alarm board once, and that was a doddle, once i had spent its value on the right kit! (solder sucker, low wattage iron, multimeter, good solder etc). I came across these boys, may be worth a punt depending on comparative costs.
http://www.electroniccarparts.com/
Its a common issue, so if you do, let us know how you go on.

 

[panason1c]

Try this also...........


http://www.tunemycar.com/index.html

 

[mercaidcarsltd]

Richard,

Just out of curiosity, how did you overcome this ?

Simon

 

[Richard.Wilson]

Well...I've not overcome it yet.
Ive been leant an old ECU from an E280 of the same year (by my local MB dealership no less), it's faulty also but I've used it to trace the faults on mine. It seems that there are "Darlington pair" transistors which are used as power amplifiers to drive the coils.
They get fried if you have a short in the loom, or a spike from the coil. So far it seems that these are the culprits.
These are a bit of a problem to remove, but I've managed to take all the ones out of the old ECU.
Mine have a different number, so now I'm trying to track down a source of replacements, as I don't fancy the £300 asking price for repairs.
They are marked
THK, then a date, BUX127 on the 2.8L
or THK, then a date, S637T on the 3.2L
Both are VDO components
Anyone know where to get them?

 

[tom7035]

Hi Richard. I'm no techie, but may be worth a look at www.CornerstoneComponents.com - they list a (close) part No. TFK S637T. Couldn't see anything like the other though. Good luck.

 

[Richard.Wilson]

Thanks for the tip,
So far I've found that these Transistors were made by Telefunken (hence the TFK), although there appears to be a maunfacturer in Germany and in China still making them, and are specific to these old VDO ECUs.
I've been searching on the web and found quite a few companies that claim to have stock. They ask you request a quote, and then try to track some down. Most have high minimum orders of about £50, although the components only cost £6>7 each.
I haven't managed to determine if there is actually a difference between the types fitted.
Not had much luck actually getting a confirmed price yet, but I'll post any "real" sources when I find them.
Regards
Richard

 

[claytorr]

I have a 1994 G36 that is giving me the same problems and I need to replace the same transistor, where did you find them?

thanks
Clay

 

[television]

The BUX 127 is a N- darlington 400v 15A 125w 1mhz made by VDU and telefunken

its the same as a BU941

 

[premmington]

I struggle to buy these componants. PM me if you find a supplier. Whole boards with everthing fitted are avail' ex Germany.

Best bet is to remove parts form donor PCB

Heat sink, coax shielding, 10 watt soldering iron, take your chance.

What have you to loose.

PM me if you want any free advice, I like helping people with DIY repairs, its how I started out.



http://www.remmington.plus.com

 

[Richard Moakes]

Is this what you need ?

http://cgi.ebay.co.uk/Transistor-BU...eZWD1VQQtrksidZp1638.m118.l1247QQcmdZViewItem

 

[sixpack]

Ecu

Hi Richard,

Output transistors are usually quite easy to test with a multimeter on ohms range. CRT type computer monitors use a similar device for horizontal drive, and when they go faulty, they invariably go dead short between collector and emitter. Darlington types are rarer but have the same failure mode. If you do try to test them with a multimeter, beware that some types have protection diode between col. and emitter (cathode to collector), dont mistake this for a short !. You cant damage a transistor with a multimeter whichever way you connect it, but dont use a megger !. Finding out if any devices read differently from others should be a good guide. Using the devices from the other ecu would probably be OK, but watch for the col. em. diodes. if the ecu uses devices with a diode, fitting ones without would probably fail.The only ecu I have ever repaired (from a bike) had fuses for each device, tiny surface mount things well hidden.

Hope this helps

Peter

 

[television]

Is this what you need ?

http://cgi.ebay.co.uk/Transistor-BU...eZWD1VQQtrksidZp1638.m118.l1247QQcmdZViewItem

Thats then one and worth buying, there are folk all over the world looking for them

 

[Aviator]

R.S. Components have a range of darlington transitors, you could check the charictaristics of these against what you require. Television gave the details.

 

[television]

R.S. Components have a range of darlington transitors, you could check the charictaristics of these against what you require. Television gave the details.

I checked with all of my suppliers before I posted and nothing in the UK

 

[Aviator]

R.S components are showing BU941 at £3.29

 

[television]

Well I owe you one, that is there, I must have done my search under the other number


Thank you very much for finding that

 

[Aviator]

Glad to be of assistance

 

[maxicab]

Has anyone tried repairing their faulty ECU in this way and had success? Any tips, especially about tracking down the faulty output pair and orienting the new transistors correctly? Are the R.S components BU941 a satisfactory replacement?
Thank you for any help.
David