Short circuit inside the ECU of a Diesel MTU genset

[angeldelangel]

I would like to ask about which could be the probable causes of a short circuit inside the Electronic Controller Unit of a MTU Diesel GENSET. A 20 Amp. fuse was protecting the ECU and it was Blown.

Any inputs are welcome.

Angel DelAngel

 

[ScottyUK]

Engine controller or generator?

 

[angeldelangel]

the short circuit heppened inside en Electronic control unit of an MTU Diesel engine.
I would like to know if any or all of these events could have contribuited to the short:

Voltage transients due to emergency stops​

doing soldering work inside the Power Control Room​

Thanks for any inputs

 

[ScottyUK]

1) Voltage transients due to emergency stops. Possible, but unlikely if the control system is properly designed and wired.
2) doing soldering work inside the Power Control Room Depends what you were soldering, and what with.

 

[angeldelangel]

Thanks for the quick replys. More information about these:

1) I assume it is properly designed and wired (from the MTU factory) but the event log of the ECU shows 70 occurrencies of emergency stops in 2 years. (too many?)

2) Some modifications indoors and outdoors of the metal structure of the PCR were done using an RX 520 electric welding machine. Probably without disconnecting the 24 DC volts of the power supply. Or even with the engine running.

 

[catserveng]

I agree that multiple E-Stops, while not good for the engine, especially the turbo's, shouldn't be an issue with the ECM. Only time I could think it might be a problem is if an auxiliary solenoid (like a fuel shutoff valve) is installed and draws current from a point in the ECM not designed for it. Have seen this on a couple of occasions.

Welding on an electronically controlled engine is pretty much a no-no, several engine manufacturers and the EMA have all provided guidelines on how the properly weld on a truck, off hiway machine or engines in other applications. When electronic engines first came out in on hiway trucks, welding was the primary cause of ECM problems, same when introduced into earth moving machines. Do some people get away with it? Lots, but it may cause a problem and the prevention is usually pretty simple.

Depending on the ECM and the engine it is installed on, a component, like an actuator, valve or other device that could in a faulted condition draw a large amount of current, can cause an ECM failure.

In standby generators, at least in my experience, the number one killer of electronic controls is still disconnecting the batteries with the battery charger still powered from it's AC source. Not only ECM's, but governors, multifunction controllers and protective devices, and monitoring equipment. Some chargers aren't a problem as they have built in surge protection, most standby systems get the cheapest stuff they can a hold of.

On your E-Stops, is the circuit normally closed or normally open? In a lot of normally closed type E-Stop circuits a loose connection or poor quality device can generate the fault. If this is a standby unit, are you having more E-Stops than actual engine runs? It is also possible that the installer used the remote E-Stop as the "normal stop", depends on your overall system controls.

Hope that helps, MikeL.

 

[FreddyNurk]

If it logs E-Stops as signals on an external input (which if I recall correctly is possible for MTU units); then subject to customer install and operation it could be logging the E-Stop every time an operator presses the red mushroom-head button. I've seen a few sites set up like this where the isolation procedure for servicing the generator included use of the E-Stop as an isolation point (I'm not getting into the argument on whether or not it is appropriate or not, although I'm not a fan of it myself).

Accordingly, 70 E-Stop events could be entirely normal for the installation.

 

[angeldelangel]

ScottyUK, MikeL, FreddyNurk, thanks a lot for your instructional words. I'm learning from all of you guys. For me, It's clear now that I hit the right place and found the smart and right people I was looking for. I'm glad about it. Let's go on:

1)The E-stop is a normally closed type. Yes, this is a standby engine with no more E-Stops than actual engine runs (more than 100). Yes, the operator pressed frecuently the red mushroom-head button to stop the engine.

So, could it be concluded that the E-Stops may be discarded as a contributing factor for the EMC failure (a short circuit)?

2) Welding in the Power Control Room. Yes, it was done at least once sometime before the failure, even that it is a no-no.

So, this event stands as a contributing factor: could it have stressed some solder that eventually melted shorting the circuit?

3) this is an issue brought in by MikeL about components like sensors and actuators. And This is the related fact: Before the EMC failure (short circuit), there was a failure in the sensor that monitors the level of the coolant: The faulty sensor was sending a erroneus low level signal to the ECM; this is programmed as an alarm, and shutdown the engine. The faulty sensor was disconnected (not replaced) and the engine was started and was running ok without the sensor for about 65 continuous hours before the short circuit happened.

So, The faulty sensor was drawing a significant amount of current that stressed some circuit segments that eventually caused the short? Could it be?

Again, thanks a lot for your replies

Angel DelAngel

 

[catserveng]

I don't know the MTU ECM's at all, but likely they are similar to most of the other larger diesel engine ECM's.

Most sensors operate on lower voltages than the input power. On one particular ECM I am most familiar with the input power is 24 VDC, the ECM has power outputs for 15, 12, 8 and 5 volts DC. Some ECM's use a single return or common for all power supplies, some use independent or isolated returns. Some returns are monitored for current to determine diagnostics from abnormal conditions, so lots of things going on in an ECM.

So you have an ECM with a "short circuit" internally. If you really want to determine the root cause you would have to figure out exactly which circuit is failed, then you work back from there to determine likely causes and run those down to determine a best possible root cause. Unfortunately most manufacturers don't provide internal ECM details, so making a good failure analysis can be hard.

Since it ran an additional 65 hours since the sensor failure you described, while it may be a possible problem, in reality, probably not. If it had been the probable contributor the ECM failure would have likely shown up soon after the repair.

Things like welding and lightening strikes can sometimes show up in strange ways, most common is some kind of corruption of the program files or base firmware, and damage to things like memory and processors.

Here is a good general guideline from the trucking industry that is in line with the EMA's and most engine manufacturers recommendations in regards to welding on any units with electronic controls,

https://www.ntea.com/docid/default.aspx?id=30228

My own experience is that power supply problems are the biggest killers of ECM's, battery chargers, jump starting with weld machines, bad grounding, failed/failing alternators, bad power connections and bad batteries are all some of the things I have found over the years in connection with "dead" ECM's.

As for the E-Stop, I will guess the unit has a programmed cooldown timer and the operator doesn't want to wait until it cycles down to finish the test run, so he punches the E-Stop, resets it when the engine dies and walks away. You might want to fix that issue, otherwise you can end up having some other problems related to the engine. I doubt the large number of E-Stops have any relation to the ECM fault unless you have added solenoid valves in the fuel or inlet air system (like Rigsavers)that draw more current than the circuit they are connected to and not protected for flyback or spikes. I did have a unit about two years ago the Fire Marshall insisted on an Auxiliary Fuel block valve that would close whenever the E-Stop was pushed, contractor wired it in without really checking with the dealer on how it should be installed, after the third "test", the E-Stop would not reset, failed the ECM input for the E-Stop. It was a big solenoid valve on a small circuit not ever designed for the current draw or the voltage spike when the coil was de-energized, but the end user wanted warranty on the ECM anyway (no, he didn't get it).

If you have field added components or circuits, make sure they are within the design capabilities of the engine control system, if you have a pretty simple package then probably not an issue.

Hope that helps, MikeL.

 

[FreddyNurk]

Number of E-Stop events, or even pushing the E-Stop, should have nothing to do with the fault described, if it is, its likely coincidental.

Only thing I can think of in that regard that might be related (but I'd wager isn't), is that later MTU units had a normally open E-Stop arrangement configuration option, with a bleed resistor so the ECM could do circuit integrity monitoring. However, if that's the failure, then its not likely the ECM would allow starting after that.

catserveng's suggestions for reasons for failure are more likely, though I'd also expect E-Stop ECM failures to show up much faster than what is described.

 

[angeldelangel]

Yes MikeL, you are right. making a good failure analysis trying to find the root cause, with missing elements, is hard work. Thanks for the guideline in regards to welding on any units with electronic controls.

In your ample and instructional reply, there are two paragraphs dense of knowledge that caught my attention:

A) 'Things like welding and lightening strikes can sometimes show up in strange ways, most common is some kind of corruption of the program files or base firmware, and damage to things like memory and processors.'

Could you alaborate a little more on this strange ways and, if possible, give and idea of how they might show up in a timeline?. I mean, do the damaging effects will show up immediately or they might show up after sometime(days, weeks)?

B) 'My own experience is that power supply problems are the biggest killers of ECM's, battery chargers, jump starting with weld machines, bad grounding, failed/failing alternators, bad power connections and bad batteries are all some of the things I have found over the years in connection with "dead" ECM's.'

In these power supply problems, 'jump starting with weld machines' and 'failed/failing anternators', how they might cause damage to the ECM?

...Or if you could give some reference for A) and B) (book or paper) to look at?

Thanks a lot

Angel DelAngel

 

[Skogsgurra]

Load dumps in general are known to kill electronics. New standards are tougher.

http://www.edn.com/design/automotive/4428059/Load-dump-protection--Old-vs--new-ISO-standards

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[redlinej]

Do you have the schematic diagram of the Ecu and fuse connection,also I would like to know if the ECU is driving any out put directly or is it through volt free relay, the input to the ecu should also be checked,because for a ECU to blow a 20 AMP fuse there must be visible signs of damage.

 

[angeldelangel]

I have the schematic diagram of the control panel, the fuse is directly connected between the 24 DC volts (two 12 volts bateries connected in series) and the input to the ECU.

Now I am trying to start the engine with another ECU from a similar engine, and I am receiving this error code: 616 ALARM EIL ERROR. I found this is an Engine Identification label error. I want to bypass or fix this error and start the engine with this ECU.

Any inputs are appreciated

Angel DelAngel

 

[catserveng]

Since your questions have moved from general in nature to specific faults codes, you really need to provide more detailed info like what is model and rating of unit and what version ECM it has. If I remember right the EIL is the alarm/protection module, and the "new" ECM can't see it or doesn't recognize it on the data link.

Most newer engine controls for large engines are in some way interlocked to prevent just swapping an ECM, this is to prevent an unauthorized ratings or emissions changes.

Almost anything in regards to most diesel engine ECM's require a factory authorized service tool, like a laptop with service software, to make an ECM swap, ratings change, electronic repairs or parameter changes.

On your previous questions, some ECM's are not very tolerant to AC voltage or high voltage spikes. In the earthmoving world, at least here in the USA, it was common for many years to jump start machines with dead batteries using the service truck's welding machine, many were rated around 28-32VDC and would work ok, at least until electronic engines, gauge panels and transmission shift controls showed up, then it wasn't such a good idea.

Some large dual rate alternators can put out pretty high AC voltages when they are failing, again saw this mostly on earthmoving equipment and in some specialty trucking applications like large wreckers with massive alternators.

I don't know of any general books or papers discussing these type problems, most of my information is from being a technician on the ground when electronic controls first came out, and the learning curves were pretty steep. I know CAT and Cummins have published a number of internal documents, like service letters and tech bulletins on these issues, but many are specific to an engine or controller family. Many engine manufacturers provide some good general information on hooking up and power supplies to electronically controlled engines in the installation and commissioning guides.

You are likely going to have to get your dealer of some other form of "factory authorized" service provider engaged to fully resolve your ECM issues.

MikeL.

 

[angeldelangel]

Thanks again MikeL for your very useful reply. I was waiting for it.

I would like to mention that as a professional, I worked more than 15 yeas in the information technology (commercial and administrative information systems) as a programmer, database administrator, and so on. About four years ago I started working in the Petroleum and Gas Industry, doing electrical maintenance to the electric systems first, and then the electronic, and control systems of some oil rigs as well. We use diesel engines from various manufacturers: Detroit Diesel series 60, Caterpillar, Cummins and MTU diesel engines.

The MTU diesel-engine generator set I am dealing with is a 250kW/60Hz/Standby/208-600V Model DS250D6SR, with an MTU ECU8 (Engine Control Unit), a DGC-2020 Digital Genset Controller from Basler Electric, and an MTU Smart Connect for data communications as the main electronic components of the control system of the engine. I got the BestComPlus software from Basler Electric as an interrogator/program and I am able to connect and get reports of the settings and logic, the event log and online meterings. Also, I can upload new settings and change the configuration with this program.

So, The replacement ECU I already installed comes from a very similar MTU engine, but I am getting the '616 EIL ALARM ERROR' when I energize the ECU. As MikeL points out, and I already found in a datasheet of the MTU Smart Connect, the EIL (Engine Identification Label) has to do with a dataset that is recorded in the EIL(?)...'The EIL ensures that only the correct Dataset can be used on one particular engine'.The datasheet goes on saying in another paragraph: 'The EIL ensures that only the data record specifically programmed for the engine concerned can be used. The engine is shut down after 15 minutes should it be necessary to use the ECU of another ECU on the ECU concerned'. Yes MikeL, The ECU and the engine are interlocked, but this is exactly what I want to be able to do: Change the interlock to be able to use the replacement ECU I already installed. So, I have the interrogator/program from Basler Electric but seems that does not have the functionality to modify the EIL Dataset. Probably I need a factory authorized service tool to make the swap, as you mention.

Any way, all additional comments on this are very welcome and appreciated.

Regarding my previous questions, I say thanks a lot again to you for your sharing. And I will search for the internal documents (service letters and tech bulletins) on those issues.

I am learning and enjoying these communicating with you guys!

Angel DelAngel

 

[redlinej]

I did some research and the EIL is located in the crankcase with a two pin connector and cannot be remove without damaging it.So i guess you have to order the ECU for that particular engine for it to work,here is a Link.Check page 16 and 17 it will explain more on the EIL.

 

[angeldelangel]

Thanks redlinej for your reply. Let me tell you that I already got the datasheet of the MTU Smart Connect that controls the communications between the ECU and the PLC (DGC-2020), and read the pages (16,17) about the EIL. Also I already found it in the crankcase of the engine.

What I would like to do now on is to search for and get the software tool to make the MTU ECU swap. If it can be done with the right tool, I would like to get that tool and do the ECU swap.

Any information about software tools for swapping an ECU/ECM component is appreciated.

Thanks to all

Angel DelAngel

 

[FreddyNurk]

Call MTU.

For obvious reasons they don't really hand out such systems to people other than their designated service technicians.

They should also be able to replace the defective ECU with one that's appropriately configured (for a replacement fee...) thus negating your requirement of swapping the ECU.

 

[angeldelangel]

Thanks FreddyNurk for this and your previous replies.

You know, I am having the opportunity from my department to try to resolve present and future issues in the MTU diesel engines we have in operation with expired guarantee.

I did not know the ECU was interlocked to the engine by the EIL (Electronic Identification Label). I am understanding that it can be reprogrammed for the engine concerned which, by the way, has the same settings. So, it seems that the issue is to associate the replacement ECU with the EIL of the engine concerned.

how to do it is what I am trying to figure out (and yes, there is a service tool to do it that MTU do not hand out for obvious reasons, as you point out).

In my present situation, I feel inclined to say that calling to MTU would be like my last resort.

Thanks for your replies

Angel DelAngel