Ford S-max 1.8TDCI Diesel Knock after exchange engine

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Ford S-max 1.8TDCI Diesel Knock after exchange engine

Postby simohandy » Mon Jan 19, 2015 9:48 pm

A colleague in our workshop has fitted and exchange reconditioned engine the a Ford S max 2007, It will run but is very harsh and has a diesel type knock, The timing has been double checked and they maintain is correct also had new DMF Clutch and Slave.
I am concerned by the dip in compression just after injection in this running scope trace attached.
Any suggestions or help from this trace?
Thanks for any advance :roll:
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Ford_S-Max_2007_Diesel_20150119-0001.psdata
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Re: Ford S-max 1.8TDCI Diesel Knock after exchange engine

Postby AuthorMike » Tue Jan 20, 2015 9:50 am

Hi,

I've taken a look and the pressure waveform clearly isn't right. I've discussed it with those more technical than I :)

Steve will hopefully be on later, as he is popping out the office this morning to a customer.

I'll ask him to give you a far better technical description of what the waveform appears to be telling us (I could tell you the piston is falling, then what looks like injection perhaps is increasing pressure?...but the time gap in injector current to the second rise in pressure I am not sure [I am not a technical expert]).

Thanks for uploading, it's an interesting waveform to say the least.
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Re: Ford S-max 1.8TDCI Diesel Knock after exchange engine

Postby Chris C Stahl » Tue Jan 20, 2015 4:02 pm

Maybe you could restrict the intake so there is a vaccum ,so that you could see the valve detail
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Re: Ford S-max 1.8TDCI Diesel Knock after exchange engine

Postby Steve Smith » Wed Jan 21, 2015 10:01 am

Hello and thank you for the post as the waveform you have uploaded does reveal an insight into events taking place inside the cylinder during the four stroke cycle.

The additional peak above TDC would appear to be the increase in cylinder pressure as a result of combustion. Here we have a concern as we are approaching the maximum input pressure of the WPS500X (500 PSI)

Would it be possible to disconnect the injector before starting the engine and recapturing the pressure waveform?

This will reveal the in cylinder pressure waveform structure without intervention of combustion.

Whilst the WPS can measure “in cylinder pressure” during engine run condition, this is for brief evaluation only and not for monitoring. The WPS has a maximum operating temperature of 80 degrees centigrade (Battery compartment) and as you can imagine this could be exceeded when monitoring in cylinder pressures with combustion present.

I have searched the waveform library for a similar vehicle and looked at other waveforms to try and match the engine type but no joy. If someone does have this engine Cam Crank waveform it would be most appreciated if they could post it here and the library.

Could you post the engine code to help with identification of this engine?

My line of thinking at present is valve timing. Looking at the compression waveform we are lacking the marginal expansion pocket that forms at the bottom of the expansion stroke. I have attached an image that should help.

2015-01-21_09-24-10.jpg


This could be attributed to an advanced exhaust valve opening and so comparing cam and crank waveforms to a known could engine would be invaluable.

Using the phase markers I can see that the camshaft position signal occurs almost 70 degrees after TDC of the cylinder you are using to measure cylinder pressure, we need to confirm if this is correct.

I have included the maths channel for the crankshaft sensor that coincides nicely with the pressure waveform TDC point and confirms high frequency noise prior to TDC (on each cylinder) from every injection.

The high pressure we can see above the TDC is responsible for the diesel knock you can hear as the pressure rises abruptly 14 degrees after TDC.

This may or not be correct for this vehicle but to reduce diesel knock we need a progressive and controlled pressure increase during the combustion event.

The injection event after TDC could be responsible for this knock as this would appear to be the main injection event that normally begins before TDC continuing through the TDC point before closure shortly after TDC, i.e. not the main injection event after TDC.

I hope this information is of some help and please feedback when you can.

Take care……Steve
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Ford_S-Max_2007_Diesel_With maths channel.psdata
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Re: Ford S-max 1.8TDCI Diesel Knock after exchange engine

Postby simohandy » Wed Jan 21, 2015 9:53 pm

Thanks Steve and others for taking the time to look through my post, and your helpful comments and ideas.

The car is now fixed, Steve you were correct the valve timing was indeed incorrect. After careful discussion and removing an injector to ascertain actual TDC (no timing marks on engine) we discovered that when the engine was timed (and rechecked), the wrong crankshaft timing pin was used! :oops:

We did try a pressure test with the injector disconnected no double towers just a single rise in pressure but still no expansion pocket.

The engine by the way is QYWA.

Tomorrow I will take a Cam/Crank waveform for future reference and post here and to the library.

Thanks again.
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Re: Ford S-max 1.8TDCI Diesel Knock after exchange engine

Postby simohandy » Thu Jan 22, 2015 9:32 am

Here is the good running Cam Crank waveform.

Thanks
Attachments
Ford_S-Max_2007_Diesel_20150122-0001.psdata
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Re: Ford S-max 1.8TDCI Diesel Knock after exchange engine

Postby Steve Smith » Fri Jan 23, 2015 1:50 pm

Great news and thank you for the follow up as this adds real value to the post.

If its not tool late, could you post the in cylinder waveform after fix with the injector disconnected and another with it momentarily connected for a comparison?

No problem if not.

Take care......Steve
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Re: Ford S-max 1.8TDCI Diesel Knock after exchange engine

Postby Jabsam » Tue Jan 27, 2015 5:50 am

May I ask a foolish question? For this is a diesel engine, where you connect the WPS500X to for the compression waveform?
Many thanks.
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Re: Ford S-max 1.8TDCI Diesel Knock after exchange engine

Postby simohandy » Tue Jan 27, 2015 11:38 am

Hi car gone back to customer sorry.

Connected WPS500x in place of glow plug using compression tester adapter :)
Note what others have said about temps and pressures.
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Re: Ford S-max 1.8TDCI Diesel Knock after exchange engine

Postby Terry Ferguson » Tue Mar 01, 2016 10:17 pm

Hi just read this post & lots of these Patterns Match the results I am Getting, I have the switching 2 cylinder misfire On the diagnostic channel, This car is Same model & engine code, What fixed this, My car has hard Knock, Made better by opening EGR, But runs on 2 cylinders only, Then switches to the other 2 cylinders, So seems all are OK Mechanically But something is Knocking 2 cylinders off The putting them back on & knocking other 2 off ?? Its an odd one, Any help is appreciated, Terry
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