No engine start - U01400 fault

[gonze]

Are the quantity control valve and pressure regulator value the ones at opposite ends of the fuel rail? Is there a way to check they operate?

Also the cable that plugs into the HPFP, what is it a connecting to? An electronic valve or a sensor?

Thank you for the help, it’s very much appreciated

 

[n10n]

Quantity control valve (aka metering valve) is part of HPFP and that’s what the wire connects to. Pressure control valve is at the other end of the rail.


Not sure how to test them.

 

[gonze]

Thanks, I have found the below post which sounds similar to my issue. Although not clear as to which sensor they refer to and if they removed it or just unplugged it.

Removed Fuel Rail.

I had an issue with cylinder 1 glow plug on CXHA engine. Replaced all 4 glow plugs yesterday. To try and make my life a little bit easier, I remove the fuel rail for access to the glows. I have Carista which has a fuel system prime function. Carista say, to be used when replacing injectors or...

www.t6forum.com

 

[n10n]

Although not clear as to which sensor they refer to and if they removed it or just unplugged it.

If you refer to the very last message of thread by @lassie I think they must have just unplugged - the pressure would not accumulate with a sensor removed

 

[gonze]

Would it be the fuel pressure sender G247 I unplug to make the pump run at maximum?

 

[n10n]

Would it be the fuel pressure sender G247 I unplug to make the pump run at maximum?

I think so yes. Interesting question, not sure if unplugging really works but my thinking goes like this:

The pressure control valve has a spring and a coil (electrical magnet), both acting in the same direction and trying to keep the valve closed. It has a natural mechanical limit pressure through spring, exceeding that pressure means valve opens and pressure is relieved to the fuel return line. The limit pressure can be increased by applying current to the coil. Both the spring and the magnet then try to keep the valve closed and hence the rail pressure can go higher than just the spring force alone before the valve opens.

Unplugging the pressure control valve means the actual pressure in the rail would not ever get higher than the spring limit force. Let's say the ECU targets to create a 200 bar rail pressure but the pressure control valve opens up already at 50 bar because it's unplugged (don't know the actual limit, this is just an example). The ECU might try to raise the pressure by letting more fuel into the rail through metering valve. And yes, there will be more fuel running through the rail but pressure will still not increase.

On the other hand, unplugging the pressure sender makes the ECU blind about what the actual pressure is. The things ECU could do in response to sender missing:

• Case "consider the fault serious enough to shut the engine off" - close the quantity valve and throttle body
• Case "pressure control valve will handle it" - send as much fuel as possible to the rail through the quantity valve in order to raise pressure
• Case "fall back to a map value" - regulate quantity valve through some factory map which is supposed to put the pressure in the right neighbourhood but is less accurate than the pressure measurement

I don't know how the engine actually handles the sender missing but as unplugging the PCV can not result in high rail pressures I think they must have meant unplugging the pressure sender.

 

[bluezie]

The 140bhp version of this engine will start and run with the regulator unplugged. It runs at a very reduced limp mode, so i would imagine this version will too. Most sensors and actuators have a backup in case they fail.

 

[gonze]

Thank you both for the responses. Unfortunately I’m on hold for a few days as my brand new Varta battery will not hold charge so I sent it back to the supplier awaiting a replacement hopefully

 

[gonze]

I am going to remove the high pressure fuel pump regulator just to rule this out and function test using a battery, does anyone know what the ohm Resistance reading should be?

 

[gonze]

back again
The van still will not start, I have bought 4x refurbished injectors and programmed them in. And fitted my replacement battery.

VCDS is showing the injectors activated, crank speed, and rail pressure looks good BUT there is no fuel coming out of the high pressure fuel pump, only a dribble.

Any ideas welcomed?

 

[n10n]

back again
The van still will not start, I have bought 4x refurbished injectors and programmed them in. And fitted my replacement battery.

VCDS is showing the injectors activated, crank speed, and rail pressure looks good BUT there is no fuel coming out of the high pressure fuel pump, only a dribble.

Any ideas welcomed?

HPFP spring snapped?

Engine cut out and wont start now.

Here is where we are at for some reason we can not clear the fault code P056200 System Voltage Low Voltage That indicates that something is still wrong. Couuld this be the reason why it's not starting, that the ECU is not getting enough power or thinks its not getting enough voltage even...

www.t6forum.com

 

[gonze]

Following your post I removed the HPFP spring and it was ok. I then used easy start to run the engine for a short time to see if any faults appeared and I had shorting/grounding faults appear for the pump regulator, rail pressure sensor and rail regulator.

When I cleared them they disappeared but I haven’t run the engine up since. I also noted when I watched the individual injector information on VCDS they don’t activate although when you view them as a group they show as activated with a duration reading.

Another day gone and no closer to finding the solution. I’m going to replace the LIN cable to remove the only fault that shows

 

[bluezie]

That sounds like you have a fault in the wiring loom, unless you switched the ignition on with all 3 items disconnected.

 

[mmi]

when I watched the individual injector information on VCDS they don’t activate

What exactly is this individual injector data?

 

[gonze]

I used VCDS to check the immobiliser status. When the engine is not cranked the status is off and when key is turned status changes to on. I assume this is correct?

I purchased my caravelle from auction with a damaged engine primarily because I liked the original spec as this would allow us to make the various changes we wished to make to enjoy the van.

Could an aftermarket second immobiliser stop the fuel system functioning? I know all the cabling on the engine and under the battery tray is untouched with no alterations. So I guess if one is installed it must be behind the dashboard, I am really clutching at straws now

I am off work Thursday and will record the individual injector data. Thanks again for the help!!!

 

[gonze]

The only other things I can think of are:

1. The timing is off. I Have seen other posts and noted a number of people having starting issues after changing the cambelt and needing to alter the timing slightly. Not sure how to check if this is required, the timing currently is correct and has been checked.

2. Fuel relay. I'm not 100% sure how to check this functions correctly, from reading its the largest relay under the battery, I forget the number.

3. This one I find strange. I get a fuel rail pressure reading which increases as the engine is cranked or run on easy start but I'm getting NO fuel from the high pressure pump to the rail. I have primed the systems more times than I can remember whilst trying different things. I have checked the flow and return pipes to the pump and these have fuel inside.

Any other suggestions welcomed........

 

[Alexwebber]

Hi.
You said it’s from an auction bought after an accident. Is there some sort of fuel cut off device to save fuel being pumped in the event of a bad enough collision… just a thought?!

 

[gonze]

Hi the van had a bent con-rod due to failed Egr rather than any accident damage.

But It does now have a flashing coil light and three beeps! Although not sure what this means

 

[Alexwebber]

Oh sorry I missed that bit on the thread

 

[bluezie]

Hi the van had a bent con-rod due to failed Egr rather than any accident damage.

But It does now have a flashing coil light and three beeps! Although not sure what this means

Ah, possibly very useful info! Did you buy it as a non runner after the EGR failed and hydro locked the engine? If so you may have spun camshafts and/or lobes = no start.
You may find you need to start from scratch on the top end rebuild, so as to eliminate everything.