Dead ECU?

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mechuccio
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Dead ECU?

Post by mechuccio » Wed May 13, 2009 1:54 pm

A friend of me who drive's a 16V Mark1 can't get the beast started anymore, the engine turns great, and sometimes we get some puffs out of the exhaust, it looks like she wants to but she can't

The engine was ideling, stopt and wouldn't start anymore.

His ECU has been changed in the past years when the car was owned by a previous owner. There is a 405MI16 ECU installed with the following number:
0 261 200 119.

I drive a Mark 2 16V, but fitted without a cat and lambda (original Belgium model) mine is a XU9J4 D6C with 158HP, my ECU's number is 0 261 200 354

I don't know much about ECU's I just like them as long as they work.
Would it be possible to fit his ECU in my BX to see if mine will start with it?
His ECU is quite oxidated on the circuitboards and we're suspecting it to be dead, but I'm not going to fit mine in his car as I'm affraid it will eat it and I rather have one dead car than two :D
You can't spell slaughter without laughter ->I just love my 16V<-

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Vanny
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Post by Vanny » Wed May 13, 2009 3:28 pm

If its oxidated on the lower side then the circuit board will be dead. Are the 119 and 354 ECU's not different connectors (ie one has three rows, the other has two rows.). I am not 100% certain, but i'm quite sure there are fundamental differences between the wiring of the 119 and 354 ECU's (being different Motronic revisions), and hence trying to swap them over could be potentially catastrophic.

It does sound like you might have a duff ECU. However it is likely that the solder has broken down rather than the circuit components themselves. You might have some luck renewing all the underside soldered joints with new solder.

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mechuccio
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Post by mechuccio » Wed May 13, 2009 3:48 pm

I don't know about the connectors yet, my ECU is in it's original place while his ECU is just located loose under the chair.
I'll check the connectors before trying to connect anything.

Also, he had a similar problem about two weeks ago, brought his car to the garage, they fitted a new TDC-sensor and distributor-cap, and then found out that the connector of his ECU was corroded, they cleaned that and the car was running fine again. 3 days ago it stopped again.

I took out the ECU and saw that the connectors where very clean and shiny so I opened up the ECU and saw this corrosion all over the circuit board. I tried to clean it with some spirits but the hazy look keeps coming back, I've cleaned some circuit boards before and they all stayed clean. So it looks as if the oxidation is inside the board.

Well, probably better to find an 119 ECU before I kill my own car as well.
Thanks for the tip M8!
You can't spell slaughter without laughter ->I just love my 16V<-

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mechuccio
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Post by mechuccio » Wed May 13, 2009 8:29 pm

Well, I've worked a bit on the car now and I think I can safely say that the ECU is dead as hell.

When starting the engine goes round a couple of times suddenly stops and then continues starting, stops again and so on. The stopping of the engine is totally random but it takes at least 4 turns.

When we disconnected the bobine the engine turned lovely with no stops.
It seems that the ECU hasen't got a clue when to give a sparksignal and does it too early detonating while still compressing the fuel.

I've made some pictures of the ECU so take a look, but I guess its complete rubbish.

Image
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Last edited by mechuccio on Wed May 13, 2009 9:37 pm, edited 1 time in total.
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Vanny
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Post by Vanny » Wed May 13, 2009 8:52 pm

difficult to be 100% sure but it looks rather like the power limiting capacitor has emptied its self all over the board as a result of corrosion. I have seen this before on a racer where the ECU was riveted to the floor of the car and when it rained the ecu ended up sat in a puddle. Killed it off pretty damn quick, swapped in another ECU and it was fine. In the end the ECU was relocated half way up the bulkhead behind the dash but easy to reach.

Personally i would be looking for a new ECU.

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Post by prm » Wed May 13, 2009 9:14 pm

A few points you may like test before replacing the ECU.

With the TDC/CAS sensor. Remove the plug from the unit.
Position the plug body with the two tags uppermost. Check the resistance between the centre and right pins. Yellow and black wires ( possibly). Should be in the region of 500-650Ω.
Crank the engine, with the distributor cap or coil lead removed.. AC voltage, about, peak 3.5-4.5 volts.AC

Splice into the main + power supplies and then outputs connections, of the main ECU and fuel pump relays, to monitor voltage while starting/running.
A section of wire, bared at one end, placed over the tags of the relays, then fit the block connector helps.

Regards

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Vanny
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Post by Vanny » Wed May 13, 2009 9:19 pm

the burnt out and scorched components on the analogue/power board would tend to suggest that the ECU is pretty dead. I dont think any amount of testing can bring it back!


That does kind of remind me though that the ANALOGUE side of the board can quite often be swapped out to other make/model boards. I know Porches of the era use very similar ECU's and can get significant performance increase by swapping there analogue board to one similar or the same as the one shown. Might give some more options when looking for a spare?

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Post by mechuccio » Wed May 13, 2009 9:32 pm

That would be great!
If anyone has any idea about a different ECU that could be used that would be fantastic.
Anyway, I'm going to completely seal mine now, I've got the sunroof which occasionaly leeks a bit, and allthoug I have the 354 model which is a bit easier to get I still wouldn't like it to die of water.
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thanuttiscotsman
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Post by thanuttiscotsman » Thu May 14, 2009 2:32 am

mechuccio wrote: When starting the engine goes round a couple of times suddenly stops and then continues starting, stops again and so on. The stopping of the engine is totally random but it takes at least 4 turns.
that sounds like when you connect the ht leads up the wrong way round! lol i would put another ecu in and see if that works! they are on ebay uk quite often surely someone will ship one to portugal or someone here will have an extra one? i have a spare but only 1 so i cant let it go im afraid.

rossco
1989 BX 16v ph1 Big project chipped, k+N, scorpion s/s, weber throttle body, Nitrous injection

1990 BX 16v ph2 (now scrapped)

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mechuccio
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Post by mechuccio » Thu May 14, 2009 9:54 am

Yeah exactly, the sparktiming is completely messed up, but she was running fin and then suddenly stopped. It looks as if the ECU just got fried. He did have some water issues in winter so it's likely that it has just been under water for a couple of weeks, maybe when this car was standing still because of the broken timingbelt, it was realy moist inside.

Well I've found a couple allready, one in Belgium, about 70 KM's from where I live and a couple on the westcoast of holland (yeah we have that :mrgreen:) so within a week she ought to be up and running again.

Also I found out that the following ECU's should be good as well:


0 261 200 119
0 261 200 125
0 261 200 139
0 261 200 140
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Vanny
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Post by Vanny » Thu May 14, 2009 10:59 am

Do you know what fitment those ECU's are for? The 139 i suspect might be a Peugeot fitment?

There are two sides to the ECU, digital and analogue. The digital side has a processor and instruction/calibration map and controls the analogue side. The analogue side has the direct interface to the car. The big heat sinked module in the pictures is the coil driver, and the other components relate mostly to the power requirements and signal conversion of the measuring devices (AFM TPS Crank etc).

Motronic 1.3 and 4.1 units do not control spark order, so the fault will not be a result of incorrect spark order (assuming the HT leads are on in the right order) as this is controlled mechanically. The ECU does control the coil, and so could potentially spark too early or too late, but still to the correct cylinder. My suspision is that the red capacitor closest to the burnt section of PCB is the control for the coil (based on the symptoms) and so the timing could well be to pot. There could however be a screw up with the injector timing.

Either way i think it does show that the digital side of the ECU is working okay, typically if this was scrambled then you would have an ECU that was totally dead and didnt put out any signals what so ever.

You could always go the whole hog and Megasquirt the car instead (MegaSquirt is an after market ECU).

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mechuccio
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Post by mechuccio » Thu May 14, 2009 12:36 pm

Yeah I was thinking about the timing as well. the order must be correct as that is regulated by the distributor cap, and the car was running fine and then just suddenly stopped.

There is another problem which is not so bad, but the rubber rings that seal the sparkplug holes are worn down, the holes were full of oil so I cleaned it as much as I could, then removed all the sparkplugs en cranked the engine a couple of times to blow it all away, and you could definitely see all injectors doing their work. Also there is a spark but it just comes at the wrong timing.

Anyway, I've found a ECU for 50 euro's and one for 75, I'm going to pick both up next week and then see what will happen. Also we should definitely change the seals underneath the valve-cap. We've built a new cilinderhead on this car in november and it has driven a couple 1000 KM's so it's not really that much oil that has been wasted, the level is always high enough but it should remain dry offcourse in the sparkplug holes :D
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mechuccio
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Post by mechuccio » Thu May 14, 2009 2:02 pm

Oh yeah, the other two numbers (125 and 139) are indeed from a peugeot. Don't know which models, but I suspect 309gti16 and 405mi16 I've got that info from the Dutch 205GTI drivers club.
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Vanny
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Post by Vanny » Thu May 14, 2009 3:10 pm

Off topic a little, but are there any BXClub NL meets over this summer? Closer to Rotterdam the better. Might be driving over late July.

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mechuccio
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Post by mechuccio » Fri May 15, 2009 11:00 pm

That would be cool!
I'll check it out, there are some things planned by the club. I'll keep you posted!
You can't spell slaughter without laughter ->I just love my 16V<-

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