T6 Cranks. Won't Start. Huge Battery Drain.

[Dilisi]

Vehicle: 2018 2.0L BMT 5 speed manual lwb 139k

When the ignition is turned on, there is a huge drain on the battery. Reported voltage from vcds goes from ~12.5v to ~11.2 and continues to drop.
Engine cranks fine but soon slows due to battery and will not start.

So far I have:
Dealt with all errors reported by vcds. I have official ross-tech cable and software.
1 problem was lin wire from battery to alternator. The yellow and green. sure enough it was broken. ( i understand this is common!! Side note.)
No other fault codes exists.
Removed / checked all fuses 1 by 1 to see if a component is causing the drain.
Removed all relays 1 by 1. Replaced with identicals from my other identical van.

Replaced ecu with that from my other van. With ignition on, no power drain, but obviously immobilised. Maybe a red herring, I don't know.

The removal of fuses was done with ignition on, so i was hoping to see the power drain stop when I removed the offending component fuse...that didn't happen. Of course removing the engine ecu fuse shut off the ignition completely.

My initial thought is that the ecu is at fault but i am no expert in this. Has anyone encountered the same or similar?

 

[roadtripper]

Removing fuses can add problems if that powers down one of the modules and it drops off the CANBUS while others are active.

If you want to chase parasitic drains (though yours sounds significantly larger than most) a non invasive way of doing it is to get a DC clamp meter and a fuse loop like this:

Laser 7384 Current Looper - Mini Type Fuses | eBay

In-Line fuse holder for original fuse. For diagnostic testing. DIY Car Service Parts. Glow Plugs. Denso Spark Plugs. Spark Plug Tools. Spark Plugs. Direct Fit.

www.ebay.co.uk

That way you can remove the fuse with ignition off, put it in the fuse loop, plug the fuse loop into the original fuse holder and then turn the ignition on as normal and measure the current in the loop with a DC clamp meter.

A DC clamp meter would potentially also allow you to trace which of the major feeds has current on it - it sounds like you are trying to find something that's a near short.

 

[Dilisi]

Removing fuses can add problems if that powers down one of the modules and it drops off the CANBUS while others are active.

If you want to chase parasitic drains (though yours sounds significantly larger than most) a non invasive way of doing it is to get a DC clamp meter and a fuse loop like this:

Laser 7384 Current Looper - Mini Type Fuses | eBay

In-Line fuse holder for original fuse. For diagnostic testing. DIY Car Service Parts. Glow Plugs. Denso Spark Plugs. Spark Plug Tools. Spark Plugs. Direct Fit.

www.ebay.co.uk

That way you can remove the fuse with ignition off, put it in the fuse loop, plug the fuse loop into the original fuse holder and then turn the ignition on as normal and measure the current in the loop with a DC clamp meter.

A DC clamp meter would potentially also allow you to trace which of the major feeds has current on it - it sounds like you are trying to find something that's a near short.

Thank you for that...I did get a clamp meter yesterday....now I know the best way to use it. Much obliged,

 

[roadtripper]

Good luck, keep us posted.

The DC clamp meters generally need to be zeroed just before the measurement is taken and work best if the cable is as central to the clamp as possible. Having said that you are looking for quite a substantial current rather than small drains so precision may be moot.

 

[mmi]

When the ignition is turned on, there is a huge drain on the battery.

Yes, there is - glow plugs draw about 100 Amps for a fraction of a second, Then just to run control units (ECU, ABS, Dash, etc) draws about 25 Amps.

Please make a VCDS data log while cranking the engine.
Details here (post #12)

Won’t start [Resolved]

T6 204 diesel. Van was used on a long drive and then a trip to the shops. It was left 5 mins and then wouldn’t start. Turns over but doesn’t fire. no fault codes. There was a slight burning smell when I parked up and it looks as if the front egr pipe has a crack, rear one has already been...

www.t6forum.com

 

[Craig.]

How old is your battery?

Is it a daily driver?

 

[Dilisi]

How old is your battery?

Is it a daily driver?

Not sure of the age of the battery and its not a daily driver. In fact its been stood for a while. Maybe a month or 2.

However, I have 2 batteries to choose from. Both are fully charged and I'm about to get the VCDS logs as instructed!!

 

[Dilisi]

Yes, there is - glow plugs draw about 100 Amps for a fraction of a second, Then just to run control units (ECU, ABS, Dash, etc) draws about 25 Amps.

Please make a VCDS data log while cranking the engine.
Details here (post #12)

Won’t start [Resolved]

T6 204 diesel. Van was used on a long drive and then a trip to the shops. It was left 5 mins and then wouldn’t start. Turns over but doesn’t fire. no fault codes. There was a slight burning smell when I parked up and it looks as if the front egr pipe has a crack, rear one has already been...

www.t6forum.com

Ok....I have made of log via VCDS as per the instructions....

To add to the mystery.....I removed the ecu cover and couldn't see anything (water staining....) so put the cover back on.
Connected the ecu and battery and VCDS.
Now, there isn't the huge power drain!!
Albeit I have disconnected the 2 cooler pumps.
I can hear a slight hum with ignition on.

Log attached.

 

[mmi]

Ok....I have made of log via VCDS as per the instructions....

Thanks.
Well, based on the log it's obvious why the engine doesn't start - the ECU does not fire the injectors (injection duration=0=RED). All the others are ok - cranks just fine, EGR, throttle, fuel lift pump, fuel rail controls, etc.




It seems that a few parameters were missing from the list - the fuel pressure might give us a clue why the ECU doesn't even try to fire the injectors.

IDE00021 Engine RPM​

IDE00347 Air mass: actual value:​

IDE00351 Main injection: start of activation​

IDE00352 Main injection: duration of activation​

IDE00407 Rail pressure regulation: status​

IDE00416 Starter control: terminal 50 feedback​

IDE00589 Fuel pressure​

IDE03767 Engine status​

IDE07757 Exhaust recirc.valve 1 bank 1: posit.feedback - Actual value​

IDE07771 Throttl.valve adapt. 1 bank 1: posit feedback - Actual value​

IDE07824 Tank-internal presupply pump 1 bank 1: activation​

 

[Dilisi]

Thanks.
Well, based on the log it's obvious why the engine doesn't start - the ECU does not fire the injectors (injection duration=0=RED). All the others are ok - cranks just fine, EGR, throttle, fuel lift pump, fuel rail controls, etc.

View attachment 228579


It seems that a few parameters were missing from the list - the fuel pressure might give us a clue why the ECU doesn't even try to fire the injectors.

IDE00021 Engine RPM​

IDE00347 Air mass: actual value:​

IDE00351 Main injection: start of activation​

IDE00352 Main injection: duration of activation​

IDE00407 Rail pressure regulation: status​

IDE00416 Starter control: terminal 50 feedback​

IDE00589 Fuel pressure​

IDE03767 Engine status​

IDE07757 Exhaust recirc.valve 1 bank 1: posit.feedback - Actual value​

IDE07771 Throttl.valve adapt. 1 bank 1: posit feedback - Actual value​

IDE07824 Tank-internal presupply pump 1 bank 1: activation​

I got 2 more logs....with fuel pressure and engine status.

 

[mmi]

I got 2 more logs....with fuel pressure and engine status.

Thanks,
Unfortunately there is no fuel pressure to the injectors - that's the obvious reason why the ECU doesn't even try to fire the injectors.
There should be close to 30000 kPa fuel pressure in a fraction of a second when cranked - now practically nothing even after a few seconds.

Log -002 below, in the log -003 (further down) there is some remaining pressure from start attempt -002 - possibly just the pressure fuel lift pump has created.

LOG -002​

LOG -003​

---

For a comparison below a proper pressure build-up - less than 0.4 seconds from start of cranking to 29500 kPa​

---

Perhaps just a snapped spring in the HPFP

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

 

[Dilisi]

Thats very helpful. Thank you so much. I will take a look at the HPFP, maybe I'll borrow it from the other identical vehicle and try it. They're twins.

I'll let you know.