2016 Mk 3 2.0 diesel Leon FR Crank no start

[Christicles]

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 mechanics, no one wanted to touch it. I got the upper guard off and was able to confirm that the belt was intact. Got an OBDeleven and scanned it for codes, was showing low fuel pressure, fuel pump and a few other errors that were related to the battery being drained from trying to start the car. Swapped the fuel pump for a new unit and took the battery out of the car to charge overnight. Fuel pump and pressure codes cleared and still couldn't get it to start. Check for codes again but all I've got showing is the standard codes that show up when the battery has been disconnected( steering wheel sensor, etc). Swapped the fuel filter for a new one and confirmed the pump is working, still cranks but no start. No new codes. I've had the vvt off to see if the solenoid was sticking and it's not moving as free as I've seen it should, so I'm replacing that next.

Can anyone think of anything else I could try if the vvt isn't the fix?

 

[SteveGSXR600K1]

Do you have any VAG indepentdent garages near you? They'd be more familiar with what the issue could be.

 

[mgrays2]

Could be many things!
You could start with injector signal. You maybe able to feel the injector click as it injects, you certainly will see the voltage change as it injects. I have a frequency (Hertz or Hz) on my multimeter and that is good for at least seeing if you have a wire changing like an injector. If the injectors are electrically pulsing, then check for at least fuel by just slightly loosing one of the fuel delivery pipes (note.. high pressure .. so do not stand anywhere near it). If you have fuel pressure and injector pulse that is a start. If no injector electric pulse it has to be ECU driven, could be many sensors, can you see the engine rpm on OBDeleven as crank/cam sensors are classic no start things but there will be a couple of sensors I would guess for rpm. The old PD Ibiza used to have a wire on the alternator that broke and killed engine, and dashboard solder that broke .. so very hard to find for your regular mechanic.

 

[ViperSlider]

Does the engine actually turn over at all when you try and start it?

 

[Christicles]

Does the engine actually turn over at all when you try and start it?

No, just a long crank trying to start then will just stop.

 

[ViperSlider]

No, just a long crank trying to start then will just stop.

So you can generally rule out any immobiliser issues.

I would seek a local VW group specialist as mentioned above as they will be better equipped to diagnose the issue.

 

[SuperV8]

Without any fault codes to guide you, it could be a number of things to cause the engine to stall & not start, unless you're an experienced DIYer they are quite complicated beyond battery and fuel filter.
Could be electrical/sensors - but I would think if your MAF or Crank sensor failed you'd get a fault code?
Was the cam belt still tight? so it can't have slipped a tooth?

when it stalled originally - would it still crank and not start? or not crank? did you get any dash warning lights?
what's the history of the car? good service history? how many miles?

 

[Christicles]

Without any fault codes to guide you, it could be a number of things to cause the engine to stall & not start, unless you're an experienced DIYer they are quite complicated beyond battery and fuel filter.
Could be electrical/sensors - but I would think if your MAF or Crank sensor failed you'd get a fault code?
Was the cam belt still tight? so it can't have slipped a tooth?

when it stalled originally - would it still crank and not start? or not crank? did you get any dash warning lights?
what's the history of the car? good service history? how many miles?

Belt was still tight. When it stalled, would crank and wouldn't start which is what caused the battery to drain with the attempts to start the engine. No warnings on the dash. I've owned the car since 2019. Done the service every year myself (Oil, filters, brakes, etc) and around 63k miles.

 

[Christicles]

So update, got the vvt solenoid replaced and now I'm able to get the car to turn over, however it will only run for a few minutes before the engine dies off. Took a video of the live data and the engine turning on.

 

[SuperV8]

Something is wrong with your fuel pressure - staying at 450kpa while you're cranking is way too low.
Notice it trips up to 710 before it starts.
When it stalls at the end it drops back to 450 - so looks like that is the lowest value.
Whether that is a real 450 - or the sensor is faulty I don't know. Sensor is much cheaper than your fuel pump!
Maybe double check your wiring to the rail pressure sensor.

Do the same test again - logging rail pressure & crank speed but in graph form so you can see it clearer.

I would say it does sound a little rough, like its missing a bit.

I get occasional long cranks (circa 2.5 - 5 seconds - nothing like at long as your cranking) and I did some logging and noticed when ever I had a long crank (left log below) my fuel pressure failed to get to 50000kpa! so my fuel pressure got to 46000, dipped down while still cranking before finally getting above 50000 and she started.
Compared to the right log when it went straight up to 50000 and started normally.
From doing lots of logs, 50000 seems to be the magic rail pressure - if it gets to this it starts straight away. Seems like the ECU waits until it sees 50000 before allowing the injectors to fire.