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jackherer

Emerald M3DK cutting out while driving due to usb to serial adaptor fault

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jackherer

My 205 running an Emerald M3DK has been cutting out totally while running recently. At very low throttle openings it runs OK then suddenly it just cuts out totally with no warning, or if I accelerate at all enthusiastically it initially picks up well but then cuts out by 3.5-4K RPM or thereabouts pretty much every time.

 

The Emerald's green light stays on suggesting that the ECU has power and that the crank sensor is still working while I coast in gear with a dead engine and then as soon as I turn the key off and on again it comes back to life every single time.  Such consistent behaviour suggests to me it isn't a loose wire. I was beginning to think it might be an ignition switch or immobiliser fault as they would be reset by turning the key off and on again unlike a loose wire which would stay loose at least some of the time.

 

But then I connected the laptop to the ECU to see what it said when it occurred and it actually lost the connection to the ECU entirely when the engine cut out and it wouldn't reconnect even after the engine came back on until I unplugged the USB lead from the laptop and plugged it back in again.

 

This made me suspicious so I unplugged the serial cable from the ECU (and it's worth pointing out that I have always left the serial cable and USB>serial adaptor connected to the ECU so I can easily plug a laptop in) and once I unplugged the serial cable from the ECU I drove for several miles without it cutting out and it would only go probably 200 metres max with it plugged in so it looks like it is the cause of the problem, some sort of failure in the USB>serial adaptor hangs the ECU which then requires a reboot! The adaptor had been permanently connected for at least a year with no issues so I'm not sure what has happened to it.

 

There is still a slight intermittent misfire and the tacho is fluctuating intermittently (but not in sync with the misfire) which I am hoping isn't because the adaptor has damaged the ECU in some way. However I had some problems with water in the HT leads not long ago so I'm optimistically wondering if that has damaged the coilpack which I am about to swap out.

 

Following mapping I had a year of trouble free running but suddenly several apparently unrelated faults have occurred at once which is really demotivating.

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barneys66

Chin up Jack - at least you have (hopefully) identified the sources.

 

Always good to get these things sorted in winter, then look forward to long summer months of cruising and abusing!

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jackherer

Cheers Barney, I'll be happy when it's sorted, it's quite close now, I had a brief burst of full power earlier which has got the motivation back really.

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barneys66

Good news - looking forward to more ride outs in 2018!

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jackherer

Yes for sure. It can't be too long until the meets at Shotley start again but I can't find the details.

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Anthony

I can understand a malfunctioning serial device causing the processor in the Emerald ECU to lock up or reset itself, which would probably manifest itself as a brief miss.  I've seen similar behaviour on other serial based devices before, especially when someone plugs something that they shouldn't into a serial port.

 

Interesting that it was able to happen without the USB-Serial adaptor plugged in though, as without a USB connection there should logically have been no power for any of the circuit inside the adaptor to do anything to the serial connection.  RS232 (assuming Emerald sticks to that standard) does have pins that have voltage on them with the port in a "ready" state though from memory, and whilst it shouldn't ever provide power to the adaptor in a conventional sense, I guess a broken / Chineseium designed adaptor could react in some odd way to that voltage.

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jackherer

It's not just a brief miss, the engine totally stops and wont restart until the ECU has had its power cycled!

 

The USB adaptor I have is actually a generally well regarded one - http://www.sunix.com/en/product_detail.php?cid=1&kid=3&gid=18&pid=1136 - made in Taiwan not China ;)

 

The Emerald serial port is wired in a non-standard way so I wouldn't be suirprised if they are doing other non standard things...

 

5a78900586f6d_ScreenShot2018-02-05at17_09_49.thumb.png.80ff0c2a4dc2608eca2e87c6cc471edd.png

 

I did make my own cable as I didn't get one with the ECU and the Emerald price is crazy but I just took it apart and it looks fine. I also took the USB adaptor apart and that looks fine too.

 

IMG_5999.thumb.jpg.7b63fce80b9413c0fb932e8d68cc45e9.jpg

 

I'm going to speak to someone at Emerald soon in case they've seen something similar before, or if they know something about how they have implemented RS232 that might be relevant.

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RossD

I've had this issue and it also had me racking my brains.

 

I pinned it down to EM interference in the loom, with I found with the help of an oscilloscope, which was feeding up to the USB / Serial converter, which then was feeding back down to the ECU.

I  fitted a supressor (choke) onto the coil positive supply and also some ferrite cores on both the serial feed and USB cable into the laptop and the problem has pretty much gone away. 

 

Worth a try..... It was worth noting I had wired my loom properly (Well according to the emerald guidelines) and was using shielded cable on the crank sensor where required. 

 

Edited by RossD
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Tom Fenton

Worth talking to emerald, if the ecu is an old one there might be updated firmware.

Paul Higgs car with an Emerald would cut out if you hit the Rev limiter and not restart until you had power cycled the ECU. Scared the s*ite out if me the first time it did it. Emailed Emerald with the serial no and firmware no from the software and they knew about it and sent me a different file. Uploaded new firmware from the file which sorted it out.

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Simes

Keiran I have been experiencing the same.

tacho doing weird things, including on occasion bouncing along to the indicators.

Missing very occasionally on WOT.

recently cut out completely, all dash lights on. Switch ignition on and off and everything fine again.

i was thinking ignition side of things,poor earthing but had never considered the ECU.

My serial lead is not plugged in.

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jackherer

Thanks for the replies, it's reassuring to know I'm not going mad!

 

It's given me a lot more to think about, EMI makes sense and as it has worked fine for a year before I had any problems it got me thinking about what else has changed recently. Not long ago I put some new ignition leads on it and had them made longer so I could move the coilpack to a 'better' location so I think I'll undo that and try the old leads and coil position to see if that affects it.

 

I'll definitely talk to Emerald about firmware too, mine is an M3DK, late enough to be upgradable to K3. I didn't bother getting the upgrade done because the price had gone up a lot and I couldn't really see any features I would use that a K3 has and an M3DK doesn't.

 

Simes, if I remember right yours is a K3 or a K6 isn't it? The indicator thing sounds like a classic earth problem, maybe you have a bad earth and that is causing EM interference or a ground loop which in turn is affecting the ECU...?

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Simes

That was my thinking.

ive REN pondering about it for quite a while, I never get a chance to work on the car these days without interruption!

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jackherer

I'm pleased to say I've just fixed this and learned something while doing it which is always good!

 

I phoned Emerald yesterday and straight away they asked what spark plugs I was using as you have to use R code ones with an internal resistor to suppress interference with their ECU. I already knew this but it got me thinking and I did some more research.

 

What I didn't know was that standard Mi16 spark plugs (I've always used NGK BCP7ET) don't have a resistor in them and therefore are incompatible with digital ECUs with the apparent exception of Motronic ML4.1! I naturally just assumed they did. Maybe the external ignition amp isolates the ECU from the ignition sufficiently?

 

The plugs I did have fitted are actually from genuine old stock Peugeot boxes and my friends Mi16 runs fine on them using ML4.1.

 

The other thing I learned is that after 1992 the plugs for Mi16s changed, I presume this is when Motronic M1.3 was introduced, they went from BCP7ET to BCPR7E - http://www.ngkpartfinder.co.uk/car_commercial_search.php?type=SPARK%20PLUGS&manufact=CITROEN&model=BX&engine=1.9 - although it says 'catalyst' in that link I'm not convinced that is the difference.

 

Anyway, the bottom line is I just fitted some plugs with an R, I only had 6 temperature 8v ones to hand so I temporarily used them and it starts and runs perfectly now and just wheelspins everywhere which is what it normally does at this time of year...

 

So looking back the problem I had started after I drove through a flood and got water in a spark plug well. I put new plugs in then due to rusty marks on the one that got wet. It turns out those replacement plugs had no resistor so they generated lots of interference and the serial cable acted as an antenna picking it up and sending it straight into the ECU.

 

With the serial cable disconnected but the wrong plugs still fitted it ran *almost* correctly. It just misfired at high RPM and even then only in higher gears it seemed.

 

Simes, when did you last change your spark plugs?

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barneys66

Impressive sleuthing - glad (mostly) sorted.

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Simes

Kieran, before I replaced the coil and leads. 3 years ago.

i think mine a standard plugs,they were dirt cheap..

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welshpug

Very interesting, Resistor type plugs don't cost much/any more, I do remember Sandy recommending the resistor type and there are 7's and 8's dirt cheap in NGK.

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RossD

Excellent. EM interference it was then!!B)

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jackherer

Yes you were spot on, I just had to work backwards to find the cause because it had been OK for a year so something had obviously changed.

 

It's running perfectly now on 6 rated plugs with resistors and I've got some of the correct 7 rated plugs on order.

 

I took it out earlier and it didn't miss a beat, my friend was testing his 205 too so we weren't hanging about...

 

IMG_6019.thumb.jpg.940c496116d7ac267cc09ad225da59c6.jpg

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Simes
On 07/02/2018 at 11:31 PM, Simes said:

Kieran, before I replaced the coil and leads. 3 years ago.

i think mine a standard plugs,they were dirt cheap..

Today was the first opportunity I've had to whip the plugs out.

BCP7ET were in there.

 

Off to get some R ones!

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jackherer

Let us know if it makes any difference to the issues you described earlier, hopefully it does!

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Simes

Will do. The leads are only 12 months old but one had got pinched under the cover so I'm replacing those too.

I'll probably do one thing at a time.

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Simes

Fancy new leads now in place.

new plugs.

no issues the doung twenty or so miles last week.

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jackherer

Excellent, that's good news. What plugs did you fit?

 

Mine was great for a while but it has a totally different issue now, a small hesitation at low revs, I've not had time to look at it though, I've been too busy with my mates 205.

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Simes

Broke down last week, missing and dying under load. New coil fitted today, same issue. I also cleaned the main earths, checked and cleaned the under dash one too. It 

idles and revs at a standstill. As soon as any additional load is added it misfires.

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jackherer

Some sort of problem with the fuel supply maybe?

 

It might be worth getting a fuel pressure gauge to temporarily put in line with the supply to the fuel rail, you can get them on ebay for very little.

 

It could be the TPS too I suppose, if that isn't working right the Emerald wont know to add more fuel. It's got to be worth plugging a laptop in to check and you can make sure the CTS is showing a sensible temperature too.

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