2017 CXHA 150ps Cut out wont restart

[Jonnyd]

Hi all I'm looking for some help please

T6 cxha 150 ps t30 120k miles

Yesterday when driving on the Dual carriageway my van cut out I lost power and managed to get onto the hard shoulder.
I attempted to restart with no joy it was cranking over but would not attempt to fire up.

No engine management light and I also did a diagnostic scan as I had it with me but not one fault found.
AA sent out a local recovery company who also scanned the vehicle with his autel scanner but also found no fault codes.

Checked timing belt was tight and intact all seems ok.

I have removed the fuel feed line at the fuel filter, turned the ignition on and there was no fuel coming out not even when cranking it over. The in tank fuel pump was not running

I checked on live data rail fuel pressure 35600 kpa which i believe is 365 bar.

Today I have tested the lift pump relay as it was not clicking. I had 12v at the common of the Normally open contact.
I tested the ecu was switching 2vdc on the yellow wire I believe the negative pin of the relay coil.
But I wasn't getting 12v power at the relay coil positive terminal so I traced this back to the fuse box and I didn't have 12v as the fuse was not pushed in.
Once I inserted the fuse back into the fuse carrier the relay started operating and low pressure fuel pump was delivering fuel to the fuel filter as it should.

I have run the lift pump to fill the fuel filter then cranked and cranked the engine over but still won't start, I have tried getting it to prime fuel through with easy start and it will run on easy start but cuts out as soon as you stop.

Checked the injectors are opening on live data
Cam and crank sensor are ok I believe
Egr valve opening
What I don't get is if the low pressure fuel pump wasn't delivering fuel to the fuel filter how was I getting 365 bar of pressure at the rail???

what I'm thinking could the rail pressure sensor be faulty and causing the fuel to return to the tank

Any help or suggestions on where to turn would be appreciated thanks

 

[Dellmassive]

If the system had run dry from the lift pump not running, it will take ages to re prime the fuel system.

So you now have a massive air lock in the system,

you have the lift pump running now?

And have fuel at the filter?

The reprime procedure shows to run the two fuel pumps in term for a few mins each and to cycle on off.

You can follow the MIS fuel proccedure here.... In the download section.

T6 & T6.1 - Diesel Fuel Supply System Workshop Manual

Workshop manual covering fuel supply system for all diesel engined vehicles This document covers removal/installation of system components like tank/pump/filters etc and also covers misfuelling procedures VIP Membership is required to download...

www.t6forum.com

..

 

[bluezie]

AFAIK, the lift pump isn't necessary for the engine to run if it's already primed and there are no air leaks. The fact it cut out at high speed, not on start up, makes me think the lift pump had not been working for a while, and it's a red herring.
If it runs on easy start, the basic engine mechanics should be good, so the issue appears to be no fuel getting injected. So either a sensor or actuator is telling porkie pies, or something is blocking the fuel from the rail to the injectors, as it's showing high pressure in the rail. You would have though any major electrical issue would log fault codes, which leaves physical blockage, eg metal particles from a broken HP pump, or water or wrong fuel.
Are you sure the van hasn't been mis-fuelled, or has water in the tank?

 

[Dellmassive]

Then you follow the fuelnto the HPFP and then to the rail.

You could crack a HP fuel line to perge air and see if you are getting HP fuel there.


Fyi, when vw replaced my engine, the dash cam showed them trying to get the vans started.

They had battery charger connected and kept turning the van over in 8-10second bursts

then pausing for 10 seconds to allow the starter and battery to cool, recover.

They must have done this 10-15 times before the engine started to splutter.

Then another 5 times before it run on its own.

So.... How long was you cranking for?

 

[Dellmassive]

As for the rail pressure PID data....

Not sure, but sounds like it's not starting from lack of fuel..

So getting the air purged is the first thing...

 

[Dellmassive]

If the system had run dry from the lift pump not running, it will take ages to re prime the fuel system.

So you now have a massive air lock in the system,

you have the lift pump running now?

And have fuel at the filter?

The reprime procedure shows to run the two fuel pumps in term for a few mins each and to cycle on off.

You can follow the MIS fuel proccedure here.... In the download section.

T6 & T6.1 - Diesel Fuel Supply System Workshop Manual

Workshop manual covering fuel supply system for all diesel engined vehicles This document covers removal/installation of system components like tank/pump/filters etc and also covers misfuelling procedures VIP Membership is required to download...

www.t6forum.com

..

Join up as VIP to access all the vw download manuals.....

VIP Membership

VIP Membership Information

www.t6forum.com

...

 

[Dellmassive]

See here too...

T6 - Mis Fuel Procedure

~manual section for dealing with a mis-fueling situation.

www.t6forum.com

.

 

[Jonnyd]

I have cracked a nut on the rail and when cranking over there is no fuel at all purging out.

I have removed the fuel metering solenoid on the hpfp and have fuel delivery from the lpfp.

The solenoid looked to me that it was normally open so I pressume it's powered shut. Is this correct or does it need to be powered open maybe as the ecu not switching the solenoid on.

I disconnected the fuel return line and there is fuel flowing back to the tank.

Correct fuel has been used i collected a couple of liters of the diesel flowing along the return line it has no water or contamination.

 

[bluezie]

Well, there's a problem - You are getting 35600 kpa showing on the diagnostic data, but zero pressure actually on the rail. I'd double check the rail pressure with the feed pipe disconnected, and also look at the rail pressure when not cranking. Both should show zero.
Also worth cracking off an injector pipe on the rail , just in case the feed pipe union has a non return valve in it, to make absolutely certain the rail is at zero.
Saying that, the rail pressure should be significantly higher than what's being reported.

 

[Jonnyd]

Well, there's a problem - You are getting 35600 kpa showing on the diagnostic data, but zero pressure actually on the rail. I'd double check the rail pressure with the feed pipe disconnected, and also look at the rail pressure when not cranking. Both should show zero.
Also worth cracking off an injector pipe on the rail , just in case the feed pipe union has a non return valve in it, to make absolutely certain the rail is at zero.
Saying that, the rail pressure should be significantly higher than what's being reported.

I have cracked of a nut on the rail and there no pressure there I'm about to test the rail pressure sensor now.

 

[Jonnyd]

Been back on the van again after work I'm 99% certain it's the fuel pressure sensor with the sensor removed its fluctuating between 0 and 200 kPa, I've checked and tested the wiring got 5v on both pins and no voltage on the ecu ground so that's ok.

With the pressure sensor installed the rail filled up really quick so have plenty of fuel delivery and the fuel pressure sensor still fluctuating between 0 and 200 kPa.

 

[bluezie]

Even if the pressure sensor is faulty, which it seems like it may be, the engine should be asking for around 200,000 kpa, but is getting nothing and reporting only 35600 kpa at best. So the pump should be flat out trying to get the pressure up, to then be regulated by the pressure regulator when pressure is achieved.
It seems there is plenty of fuel present at the rail, but at low pressure, which points to the pump having failed, or the regulator has failed and is bleeding off all the pressure.

 

[Jonnyd]

Even if the pressure sensor is faulty, which it seems like it may be, the engine should be asking for around 200,000 kpa, but is getting nothing and reporting only 35600 kpa at best. So the pump should be flat out trying to get the pressure up, to then be regulated by the pressure regulator when pressure is achieved.
It seems there is plenty of fuel present at the rail, but at low pressure, which points to the pump having failed, or the regulator has failed and is bleeding off all the pressure.

Thanks for the reply and what you have said makes sense and may well be the issue.
Im going to fit a new sensor tomorrow as what I'm thinking is there could be pressure at the rail but if the sensor has failed we wouldn't know what is actually at the rail.

 

[Dellmassive]

Seems there is two engine threads going on ATM.

One as a non runner and one as a lumpy cold runner.

Must make sure to not got get them confused.

Do you have access to vcds?

We may be able to have a look at some block data? ... @mmi

.

 

[Jonnyd]

Seems there is two engine threads going on ATM.

One as a non runner and one as a lumpy cold runner.

Must make sure to not got get them confused.

Do you have access to vcds?

We may be able to have a look at some block data? ... @mmi

.

I've just ordered a vcds kit from gendan will hopefully be here tomorrow i will try and get it setup is there a how to on here for what you will need from me.

 

[Jonnyd]

Changed the sensor today and now I'm getting a fuel pressure reading.

I have purged the lpfp system for 2 minutes and have no air in the fuel return line so the hpfp is full.

I have cracked a nut on the fuel rail at the bottom of the injector pipe and cranked the engine in the matter of second it was full with fuel and purged the air out.

It takes around 10 seconds of cranking the engine before pressure starts to build then the injectors open and it's fires and splutters and stops and the starter motor tries to take over again but dies.

I have done this maybe 6 times but my battery is dieing so have stopped for today to charge again.

Is it normal for the rail pressure to go back to zero after i stop cranking?

I have a video of the diagnostics but it's too large to load on here is there a way I can show you all.

 

[Dellmassive]

To do videos, you need to load them on YouTube or other. . .

then post the link here.


+++++++++


starting to sound like faulty HPFP?


+++++++++

 

[Dellmassive]

Is it normal for the rail pressure to go back to zero after i stop cranking? - Yes.


+++

Start up fault

Really happy with the help so far - have never received any remotely useful input from the dealership. But in there defence they never observed it faulting first hand only my videos. VCDS has been fantastic so far - only my inexperience limiting it. Reading the comments on the time stamps does...

www.t6forum.com

+++


thanks to @mmi , we have some excellent data charts that show whats going on. .

here mine doing a rail pressure build at start. . . . .






and now engine running. . .








,,,,,,


and:

fuel rail pressure at shutdown . . .

was 29600kPa @ 820rpm tickover.

at shutdown rmp=0 rail pressure starts to drop.

by 20seconds later rail pressure dropped to half 1600kPa

by 30seconds later rail pressure dropped to min 800kPa

by 40seconds later rail pressure dropped to min 500kP

final resting rail pressure is 200kPa

 

[Jonnyd]

Is it normal for the rail pressure to go back to zero after i stop cranking? - Yes.


+++

Start up fault

Really happy with the help so far - have never received any remotely useful input from the dealership. But in there defence they never observed it faulting first hand only my videos. VCDS has been fantastic so far - only my inexperience limiting it. Reading the comments on the time stamps does...

www.t6forum.com

+++


thanks to @mmi , we have some excellent data charts that show whats going on. .

here mine doing a rail pressure build at start. . . . .


View attachment 271683



and now engine running. . .


View attachment 271684





,,,,,,


and:

fuel rail pressure at shutdown . . .

was 29600kPa @ 820rpm tickover.

at shutdown rmp=0 rail pressure starts to drop.

by 20seconds later rail pressure dropped to half 1600kPa

by 30seconds later rail pressure dropped to min 800kPa

by 40seconds later rail pressure dropped to min 500kP

final resting rail pressure is 200kPa

View attachment 271685

Do you not think it possibly could still have air in the system as when the injectors open the pump holding it at one point was 1020 bar or 102,000 kpa it only shows as zero when it stops turning

 

[Jonnyd]

I'm going to test the fuel pressure control valve tomorrow see if there is any fuel bypassing the valve.