P00C6 "Minimum pressure not reached" Possible bad HPFP?

[nshrose]

Hello all,

We are having an issue getting this engine to run. I will lay out the details below. Please take a look and provide feedback.

Component	Vehicle As-Is	Vehicle As-Received	Donor
Engine	2010 CJAA from donor	2012 CJAA	2010 CJAA
Transmission	2010 6spd Manual from donor	2012 DSG auto	2010 6spd Manual
ECU	2010 Manual from donor	2012 Auto	2010 Manual
Tune	Malone Stg 2, DPF delete, IMMO delete, swap related deletes; Tied to this ticket.	Stock	Stock
Engine wiring harness	Original 2012 modified; We swapped the 2012 engine harness on to the 2010 engine and added the clutch position switch wiring	Stock	Stock
HP Fuel Rail	First crank - 2012 rail Currently - 2010 Rail	Stock
Notes:	On first crank the engine fired for 1-2 seconds, and then it hasn't fired since. When monitoring Measuring Block 20, we noticed 0 bar pressure at the fuel rail during crank. Unplugging that sensor and re-connecting it seemed to make it work briefly but it would return to reading 0 after a short time. Checking DTCs showed P06A3 "Sensor Reference Voltage D" open circuit, and our reading indicated that this could come from a bad sensor. This led us to swap the fuel rail over. After swapping the fuel rail over, we used VCDS to run the auxiliary fuel pump a few times to bleed the air from the system. Now the P06A3 code is gone, and we instead have P00C6 "Minimum pressure not reached". Watching VCDS measuring block 20 during crank, the fuel pressure actual reading stays at or below 16 bar with the command pressure being around 400 bar. Important to note that there was no traces of metal in the filter housing, metering valve and common rail. Have you ever seen something like this before? We have ran the aux pump cycle plenty of times trying to bleed air out of the lines and I even cracked the injector lines while that was running, just to be sure. Conclusion: We think it could be one of the following three potential causes, but are open to other suggestions. There's trapped air in the rail causing a vapor lock that keeps the injectors from firing (corresponding with some posts we have found on this topic) The ECU is not commanding the injectors to open. Possible crank position sensor signal issue? There's no code to indicate this but I could see it as a possibility The 2010 ECU is not compatible with the 2012 harness. We have the factory wiring diagrams, but do not have an ECU pinout so this is difficult to verify

 

[vwildvr6er]

I look forward to getting this resolved.

 

[oilhammer]

Not sure on what models you are dealing with here. A 2010 Jetta sedan (A5) and a 2012 Jetta sedan (NCS) are two completely different cars. And they have two completely different engine harnesses, despite both being CJAAs. The Jetta wagon is still an A5 platform, even in 2012.

I don't think much of that should matter for the ECU specifically, though. What cars are we talking about here? What are you doing (start from the beginning with a brief synopsis, it may help).

 

[nshrose]

Not sure on what models you are dealing with here. A 2010 Jetta sedan (A5) and a 2012 Jetta sedan (NCS) are two completely different cars. And they have two completely different engine harnesses, despite both being CJAAs. The Jetta wagon is still an A5 platform, even in 2012.

I don't think much of that should matter for the ECU specifically, though. What cars are we talking about here? What are you doing (start from the beginning with a brief synopsis, it may help).

2010 AJ9 Sportwagen
2012 AJ5 Sportwagen

We have swapped the 2010 CJAA and 02Q into a 2012 that had a CJAA and DSG in it. Everything is swapped over correctly and wired correctly. Clutch position sensor works. We ended up taking the engine harness off the 2012 motor because it has some differences vs the 2010 body harness that gave us issues with the AUX pump not running. On initial harness swap over the car briefly fired, and we have not been able to get it to sense then.

Sorry for the edits.

 

[oilhammer]

OK, so A5 to A5, automatic to manual.

Was the '10 engine running when you took it out? Do you know any history on it? Did it get a new belt put on? Check the inlet screen in the little black plastic nub on the inlet fuel line assembly (right before the HPFP).

What about the intercooler? Was it checked for anything inside beforehand?

 

[vwildvr6er]

OK, so A5 to A5, automatic to manual.

Was the '10 engine running when you took it out? Do you know any history on it? Did it get a new belt put on? Check the inlet screen in the little black plastic nub on the inlet fuel line assembly (right before the HPFP).

What about the intercooler? Was it checked for anything inside beforehand?

Yes, the '10 engine was running when we took it out. It has about 182k on it. A timing belt service was performed while it was out. The inlet screen was checked earlier in this process and it was backflowed with pressurized air to see if it had captured any metal particles.

The first attempts at firing have been without the cooling stack, so no intercooler in the system at the moment.

 

[oilhammer]

Verify the timing belt and tensioner are still correct? Probably not the issue, but it does happen:

Weird start problem cjaa

Hey guys, I redid the timing belt and water pump on my 2013 Jetta TDI using the guides here and got the car to start just fine. It would slowly crank then finally turn over, almost like the battery was low. Since the battery voltage was low and over 3 years old, I replaced it. Now the car will...

forums.tdiclub.com

Also, and again, not your problem as I don't see it causing a no start, but the injector numbers have to be input to the ECU, if they've been mixed around.

 

[vwildvr6er]

Verify the timing belt and tensioner are still correct? Probably not the issue, but it does happen:

Weird start problem cjaa

Hey guys, I redid the timing belt and water pump on my 2013 Jetta TDI using the guides here and got the car to start just fine. It would slowly crank then finally turn over, almost like the battery was low. Since the battery voltage was low and over 3 years old, I replaced it. Now the car will...

forums.tdiclub.com

Also, and again, not your problem as I don't see it causing a no start, but the injector numbers have to be input to the ECU, if they've been mixed around.

Timing: I've been thinking that we need to verify the pump is timed correctly, so we will do that.

Injector coding: In theory, these should be coded correctly already. I say this because the engine and ECU are both from the donor vehicle.

 

[nshrose]

Verify the timing belt and tensioner are still correct? Probably not the issue, but it does happen:

Weird start problem cjaa

Hey guys, I redid the timing belt and water pump on my 2013 Jetta TDI using the guides here and got the car to start just fine. It would slowly crank then finally turn over, almost like the battery was low. Since the battery voltage was low and over 3 years old, I replaced it. Now the car will...

forums.tdiclub.com

Also, and again, not your problem as I don't see it causing a no start, but the injector numbers have to be input to the ECU, if they've been mixed around.

Thanks for the replies.

The ECU matches the engine and injectors. The fuel rail has been swapped from the 2012 motor to the 2010 motor tho. This got rid of our first code and then produced the minimum fuel pressure code.

 

[oilhammer]

I no longer have ETKA (that computer finally died), so I cannot look stuff up... BUT .... VAG is pretty good about putting part numbers on just about everything. Can you see any on the rail pressure sensor and rail pressure regulator and verify they are the same?

 

[vwildvr6er]

I no longer have ETKA (that computer finally died), so I cannot look stuff up... BUT .... VAG is pretty good about putting part numbers on just about everything. Can you see any on the rail pressure sensor and rail pressure regulator and verify they are the same?

We will have to check that and get back to you. We swapped it because the original sensor seemed to be functioning intermittently. It would display 0 bar at all times accompanied by the P06A3 code. We noticed that we could unplug the connector and plug it back in, and it would briefly read a value similar to the commanded pressure (~380 bar during crank). I swapped the rail and bled it as well as I could, but I am still open to the idea that it is vapor locked.

 

[nshrose]

I no longer have ETKA (that computer finally died), so I cannot look stuff up... BUT .... VAG is pretty good about putting part numbers on just about everything. Can you see any on the rail pressure sensor and rail pressure regulator and verify they are the same?

Oilhammer,

On our thought of vapor lock, what are your thoughts of using WD40 for assist in starting and see if it will build pressure and run itself?

 

[oilhammer]

I don't think diesels do that.... the injectors self vent, and it should be able to build rail pressure within a few seconds. They do need to be cranking fast... any weak battery, slow crank, etc. will make it worse.

 

[nshrose]

SOLVED!

I don't think diesels do that.... the injectors self vent, and it should be able to build rail pressure within a few seconds. They do need to be cranking fast... any weak battery, slow crank, etc. will make it worse.

vwildvr6er and I did a small amount of tinkering tonight and verified timing was correct. Unplugged the glow plugs and shot a small amount of starting fluid into the intake and it fired and stalled. One more very quick shot and it fired, ran and sustained perfect desired fuel pressure. It was trapped with air. Thanks for the help Oilhammer.

 

[vwildvr6er]

@oilhammer what Nick said above. Thank you greatly for your quick feedback and input!