[delfry]

Hi,

I've recently replaced driving chains in my N47 engine.
After completing the job engine cranks smoothly but won't actually start.

There are no fault codes stored in computer.
I have a new battery and I've checked whole fuel system in terms of leaks and proper fuel pressure.

I've conducted a diagnosis of starting procedure with the help of ISTA+ software and it seems that everything is as it should be:

Here is a diagram - test results - with legend:
https://drive.google.com/file/d/1z3p...VXbR9kBBr/view

https://drive.google.com/file/d/1tmn...7v_lG3QSG/view


I have no clue as to what else there is to check? Any suggestions?

Chris

[Eddamoo]

Sync status looks ok so that suggests the engine is in time.

Did you remove fuel lines to move the engine? Has the system bled through correctly? You can see the rail has pressure, but are the injectors actually firing ok?

I would probably pull a glow plug and take a look down the bores. Diesel will fly out of the hole so be careful.

[delfry]

I had to disassemble fuel lines as it's necessary to get to camshafts. After putting it all back together i bled the fuel system and checked pressure using software. Its ok.
I don't know if injectors fire properly (they should as they worked perfectly before and its basically impossible to misplace their connectors).

You advise to look down the bores to see whether injectors are working properly?

Is there any other way to check them? (it's supposedly not advised to unscrew glow plugs on cold engine)

[delfry]

There is also one thing that seems suspicious about diagram I've sent.

"Engine start status" changes from value 2 to 6 during cranking and then goes to "0" whereas according to bmw description only possible values are 0,1,4,8,32,128.

I'm not sure how to interpret that.

[Eddamoo]

Originally Posted by delfry

There is also one thing that seems suspicious about diagram I've sent.

"Engine start status" changes from value 2 to 6 during cranking and then goes to "0" whereas according to bmw description only possible values are 0,1,4,8,32,128.

I'm not sure how to interpret that.

I think you're looking at the wrong axis? It looks to jump from 8 to 64 to me (Y-Axis 2). Those are both Base2 numbers which seems to be the sequence (0, 1, 2, 4, 8, 16, 32, 64, 128 etc).

I cant think of an alternative but to look/smell down the bores. You could try cracking off the fuel lines closest to the injector to see if fuel is there?

Diesels only need compression and fuel so it must be the fuel. Its either not being delivered or being delivered at the wrong time.

[delfry]

I will check the injectors in terms of fuel delivery.

But there is sth off at the diagram, it's "Y-axis 3" and light blue colour to look at, and it's definetely 2 and 6 instead of lets say 0 and 4.
It's presumably ok, as it drops to 0 (no problem detected) at the end, and "synchronisation status" is 30 (synchronisation OK) but still, kind of strange discrepancy between chart and its description.

[Eddamoo]

Ahh apologies i was just looking at "Engine Status".

One more thing to explore. The Low Fuel pressure (grey) - that seems to be just above 0 bar. A quick google says that this should be around 4 bar but i dont know if thats while the engine is running or not.

If i get time later ill check the pressure behaviour of my LPFP.

[delfry]

You are right about Low Fuel pressure indication. Havent noticed that.

But I did check whole fuel system independently prior to this test also using ISTA+, and it told me that it's above 4bar in low pressure part and a bit above 250bar in high pressure part, which is supposed to be just right.

Seems that somehow not all of the information in this software is reliable.

[bmwPower99]

This might sound a bit silly but can you turn the engine easily via a breaker bar on the crank.

[Enabled]

Originally Posted by delfry

You are right about Low Fuel pressure indication. Havent noticed that.

But I did check whole fuel system independently prior to this test also using ISTA+, and it told me that it's above 4bar in low pressure part and a bit above 250bar in high pressure part, which is supposed to be just right.

Seems that somehow not all of the information in this software is reliable.

On diesels with a lot of air introduced into the fuel rail and the fuel lines to the injector, software bleeding is often not enough to get it to start.

I have had to crack open all the fuel line to injector nuts just enough to allow air to escape while cranking. When they all leak a bit of diesel instead of air, the engine is ready to fire up.

If the rail pressure does not reach the 200-250mbar threshold, the ECU will not actuate the injectors. An air pocket can cause this.

[delfry]

Originally Posted by bmwPower99

This might sound a bit silly but can you turn the engine easily via a breaker bar on the crank.

That's an interesting angle - but I did change the timing chains on this car by myself, and I had to manually crank the engine in the process - it went smoothly and starter has no problems turning it as well.

Adding manually "fuel" to the air intake line is an idea I might try though. Thanks.

[bmwPower99]

This guy had issues starting but he just kept on trying and it eventually started. skip to 15mins.

[Enabled]

Originally Posted by bmwPower99

This guy had issues starting but he just kept on trying and it eventually started. skip to 15mins.

If you release the air, it will start much faster.

[delfry]

I was just going to try and realease the air manually as you suggested, but decided to do the software bleeding once more first, and than i rerun the starting test procedure.

And well... there are no errors on the diagram this time. Low pressure indication is as it should be (building up to 4bars), and "Engine start status" jumps between values described in the legend... but it mean it jumps from 0 (fault could not be found) to 4 (there is sth wrong about synchronisation) and back to 0.

https://drive.google.com/file/d/1QSn...ew?usp=sharing

I rerun the test again to the same effect.

And that worries me as perhaps somehow, even though "Synchronisation status" says it's OK, there may be sth amiss about it.

I've cranked the engine multiple times by now, so probably I'm not able to damage it any further though. I will proceed to try and bleed it manually and crank it for longer period..... we will see what happens

[Enabled]

Does any fuel come out from the injector hard pipe when cranking with the nuts mildly loosened?

[Eddamoo]

I'm unsure what the sync status codes mean, where are you referencing them from? The engine sync status looks to be 30, any idea what that means?

When you had the engine apart, is there any chance you could have it 360 degrees out of time? I.e you aligned tdc on the incorrect stroke?

[delfry]

Originally Posted by Enabled

Does any fuel come out from the injector hard pipe when cranking with the nuts mildly loosened?

Yes, I've just checked it does, and there is no air or air bubles visible.

I'm slowly coming to a painful conclusion that there actually might be a fault in synchronisation between crankshaft and camshafts, and so I will have to disassemble everything again

[delfry]

Originally Posted by Eddamoo

I'm unsure what the sync status codes mean, where are you referencing them from? The engine sync status looks to be 30, any idea what that means?

When you had the engine apart, is there any chance you could have it 360 degrees out of time? I.e you aligned tdc on the incorrect stroke?

Explanation of all of those values are in my first post in the second image i had sent.

[Jackmorgan161]

Hello i am facing a similar problem with my car after i replaced the timing chain, glows plugs and module. I was wondering how would i be able to check my Engine start trace to ensure that all pressures and timings are correct.
I also changed the injectors but did not code them could it be the problem
Thank you for your help.

[delfry]

My problem is solved!

After making sure that synchronisation is physically ok (removing head cover and checking for proper alignment on camshafts while having crankshaft in TDC) I've managed to start the engine using starting fluid sprinkled to the intake manifold (in my case it was super flammable cockpit polisher ).

It still didn't run properly though, and there was no reaction to gas. No reaction whatsoever even though I haven't touched anything connected with throttle and gas pedal during the repair. Engine has started a few more times (on its own), but it strugled to run properly even after thorough physical bleeding.

It turned out that the reason for those problems had been connected with new pressure sensor that I'd installed on the fuel rail. I did that because the computer was showing a fault code indicating wrong fuel pressure when I was trying to start it for the first time. In fact it was probably due to air in the system. My mistake was that not only I've changed that sensor unnecesserally but I also replaced it with one made by Maxgear.

Replacing sensor to the original one, solved all problems and engine runs as it should.

[delfry]

Originally Posted by Jackmorgan161

Hello i am facing a similar problem with my car after i replaced the timing chain, glows plugs and module. I was wondering how would i be able to check my Engine start trace to ensure that all pressures and timings are correct.
I also changed the injectors but did not code them could it be the problem
Thank you for your help.

Search for an "Expert Mode" in Ista+. One of its modules is called "Engine start". That's what I was using.

To input proper injection compensation for each injector go to Service functions/Power train/Digital Diesel Electronics/Adjustmen functions/Injection quantity compensation.

[Watsey]

delfry all that unnecessary work because of an incompatible sensor

Great to see that you managed to get the problem sorted.