2.0TDI CR184 CUPA - Long Crank / Low Fuel Pressure

[HyperXChaz]

Hi all and my apologies - I know this has been discussed many times before as I have been reading endlessly. Problem is I have seen different solution for the long crank such as new battery, battery reset, EGR etc but i don't think my problem is with any of them. I have been having intermittent long cranking since i bought the car in 2022 but the past few months it has gotten worse to be pretty much every time i start the car after it resting overnight and it can take anywhere from 5-15 seconds for it to start. But it ALWAYS starts. Thought it was "One of the characteristics" of the car as suggested numerous times. Then i read it could be the VVT / Cam adjuster - But i don't have a VVT solenoid or housing.

Looking for some advise as to me - logically - It can only be Fuel pressure, and i think i am right.

Only happens on the first cold start of the day, after that, it starts first time, everytime.

It's not the egr (That was already replaced anyway last yea due to coolant leak). It's not the battery because it cranks for ages no problem. It's not the starter because it's turning fast enough. I suspected low fuel pressure a leak in a seal somewhere low pressure. i.e. Leak off pipes causing fuel to drain slightly back into the tank. I'm thinking injector leak offs because if it was anywhere else it would start, then cut out and not start without cranking again for ages, surely.

Plugged in VCDS this morning before i started it and logged 7100 hPa / 7.1 Bar for "Fuel High Pressure Sensor: Actual" - Started the car and it cranked for a good 10 seconds and only started when sensor:Actual reached 44000 hPa / 44 Bar. So i'm pretty much certain it is fuel related.

I'm going to change the fuel filter tomorrow and maybe change the 'o' ring seals on the injector leak off return pipes where they connect to the injector.

Does anyone else have any other ideas / suggestions?

Thanks so much


Also - Here is a copy of the Quick Scan as i see most people ask.

 

[SuperV8]

I have the same symptoms & engine.
It always starts, Has never not started - but sometimes when cold it cranks for long enough for me to turn to my misses and mouth some expletive!
Again - on a hot crank it has never done it.

I noticed on some fuel rail pressure logging I did that on a long crank (in this case around 2.5 seconds - left graph) it didn't get past 50,000kPa, and only fired when it got to 50000kPa - where on a normal crank/start (right graph) it went straight past 50,000kPa and fired straight away.

The rail pressure is controlled by the control solenoid on the HP pump and fine tuned by the pressure regulating valve on the rail 057130764AB.
My current 'best guess' is maybe this rail pressure valve is 'playing up' - trouble is they are quite expensive to just throw one to see, and the control solenoid is even more expensive.

2016 Mk 3 2.0 diesel Leon FR Crank no start

Hi All, My Leon broke down on Boxing Day and it's been a bit of mare trying to get it fixed. I was idling at a set of lights and the engine just stalled out. Couldn't get it started again and had to get my dad to tow me back to my house. I was worried it was a timing belt and phoning the local...

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[HyperXChaz]

*Update* - I changed the whole injector Leak off pipe(s) thinking the seals must be failing. (They were slightly flattened / less full and round when I removed the old one).

Issue still persists.

Strangely - on a cold start, it can crank for 10-20 seconds before starting / getting the fuel pressure to spec.

However - I have also noticed that if I let it crank for a second or two, then key out and try Again it starts straight away, or at least after another second or two. much faster than just letting it crank to oblivion.

Looking for further suggestions / ideas

 

[DEAN0]

*Update* - I changed the whole injector Leak off pipe(s) thinking the seals must be failing. (They were slightly flattened / less full and round when I removed the old one).

Issue still persists.

Strangely - on a cold start, it can crank for 10-20 seconds before starting / getting the fuel pressure to spec.

However - I have also noticed that if I let it crank for a second or two, then key out and try Again it starts straight away, or at least after another second or two. much faster than just letting it crank to oblivion.

Looking for further suggestions / ideas

Go to 17 mins on this video - he shows how the VVT part has been re-designed.

 

[HyperXChaz]

Go to 17 mins on this video - he shows how the VVT part has been re-designed.

My car does not have the VVT mate

 

[Compo1]

However - I have also noticed that if I let it crank for a second or two, then key out and try Again it starts straight away, or at least after another second or two. much faster than just letting it crank to oblivion.

Looking for further suggestions / ideas

This is exactly how i deal with the issue very short crank then re crank and mine starts straight away doing so, i just live with it.

I guess you could log fuel pressure on the second crank with the above method.

I've also read but never investigated that this issue is down to oil pressure or the car waiting for enough oil pressure to register at the sensor before allowing the car to start. I don't remember the forum only it was American.