[CraigTAus]

Hi,
Well, I have my first problem that I am hoping the forum can assist me with.

I have recently taken ownership of a 2012 build MY13 TDI with 138000 kms. I have only done around 500kms in it so far but have experienced an issue twice where the return fuel line from the injectors has blown off at the pressure retention valve.

Both times this occurred in similar circumstances.
- Had been driving the car for about an hour
- Accelerated reasonably hard and suffered a loss of power wth some shuddering
- No error codes were generated or warning lights came on

In both cases the same hose had blown off and fuel has leaked all over the engine and down into the V of the engine. ( the first time it happened, I was able to suck out over 2 litres of diesel from the v between the two cylinder banks)

In both cases, refitting the hose, allowed the engine to run properly again. If I drive the car 'sedately' then the problem has not re-occurred.

I have tried searching for similar problems with minimal success. I did find this thread in another forum where the OP confirmed that a part in the fuel pump was replaced which fixed the issue (Possibly the Fuel Metering Valve ???)

One thing that makes me think the issue may have been there for the previous owner is that the 2 inlet hoses and the 1 outlet hose on the pressure regulation valve plus one hose connection on the right bank of cylinders (when standing at the front) have steel hose clamps fitted. All the other hose connections on the turn lines at the injectors are just hoses pushed onto the barbed plastic fitting. I have attached pictures (I hope)

I have read in VW SSP 820133 that the pressure retention valve generates a back pressure of between 3.5 and 10 bar to the injectors.

I am obviously getting too much pressure in these lines and it is causing the hose to blow off (even with a hose clamp).

So the question is, what could be causing the excessive pressure?
My thoughts are:
- faulty pressure retention valve restricting the flow and causing higher than normal back pressure
- one (or more) injectors having too much flow into the return line which then causes a higher than normal pressure drop through the pressure retention valve and results in too much pressure
- A restriction somewhere else in the fuel return line after the pressure retention valve. The hose out of the pressure retention valve runs to a banjo fitting on the injector rail where it tees in with the outlet of the Fuel pressure regulator valve N276 and then back to the fuel filter housing at the left rear.
- Pressure regulator valve N76 dumping high flow into return line causing higher than normal back pressure.
- Problem with something in the fuel pump as per the linked post above? There doesn't seem to be a direct connection between the pump and the return line so unsure how this could cause it.

But how do I determine which one it is?
I do have an OBDeleven (like VCDS) - Is there something I can measure?

Do others have any hose clamps on their return line hoses?

Has anyone experienced this or heard of it happening? Any links to threads?

Thanks in advance
Craig

 

[CraigTAus]

Ok, so had a look through the live data I could log and found tags for "Injection amount deviation cylinder x" for cylinders 1-6.
So I logged them at idle and also went for a short drive.
Without knowing much about these values I am thinking cylinder 2 and 6 look abnormal.:frown2:

 

[CraigTAus]

Any thoughts/suggestions ?

Can anyone confirm that they don't have hose clamps on their return line hoses, maybe a photo?

Thanks
Craig

 

[CraigTAus]

Nobody with any opinions/suggestions?

 

[Dajjen]

I've had the same problem on my Q7 with CRCA engine. It started with refueling in a different place than normal and after that i've changed 3 fuelfilters. The engine didn't respond to hard acceleration, it died, and i blow the small hose from n1 injector, the same as you have clamped on picture n2.

 

[murray]

Good Morning,

I had my '14 Cayenne CD in for EGR Valve and Manifold cleaning, the original return line directly off the common rail was reinstalled without a clamp.

This is how VAG what tech's to install; without a clamp, I actually saw the Memo.
Of course it blew off, fuel everywhere.

They tried clamping it with factory device especially ordered, the hose was still not tight, you could still rotate it on the spigget.
I was in the workshop and suggested it was probably because, the inner hose and spigget were coated with fuel making it slippery.

This is when the mechanic flushed both the spigget and inner hose with brake clean. Once evapporated the hose now was tight to push on, and with a small regular spring slotted clamp it's been perfect ever since. A regular worm drive clamp won't work!

An Old Dog born in the fifties, teaching some young Guy a trick or two!

Cheers and good luck

 

[CraigTAus]

Haven't solved this yet but hasn't happened again yet. Need more time to tinker. Thanks for the suggestions.
Have a new issue to sort out now. Separate post coming

Craig

 

[CraigTAus]

Just a followup post on this issue.

A couple of months back I ha injector 6 fail and needed be replaced.
Have not determined if this is related to the initial problem, but it is on the same cylinder bank as the return line that down off previously.
The injector had a lower resistance than the all the others and also had a short to the casing which caused the engine light to come on and went into limp mode.

I haven't got around to trying to simulate the previous issue since the injector has been replaced.

 

[ToolmanJohn]

Just found this thread. My 2013 TDI popped a fuel return line from cylinder 4. Didn't know why it lost power and was undriveable, leaking diesel when running (A LOT), so flatbed to dealership, and they diagnosed loose fitting at the injector 4, they clipped it back on. I had the EGR cooler assembly replaced (coolant leak) under warranty 3 months ago (January), they had to remove the fuel lines altogether and reinstall them, so obviously, it was a mis-fitted fuel return line.

I am not sure how the clip works, I looked at it, it looks like a T fitting of some sort with a hose fitted to it attached to the injector near the injector fuel pipes.

 

[CraigTAus]

Just found this thread. My 2013 TDI popped a fuel return line from cylinder 4. Didn't know why it lost power and was undriveable, leaking diesel when running (A LOT), so flatbed to dealership, and they diagnosed loose fitting at the injector 4, they clipped it back on. I had the EGR cooler assembly replaced (coolant leak) under warranty 3 months ago (January), they had to remove the fuel lines altogether and reinstall them, so obviously, it was a mis-fitted fuel return line.

I am not sure how the clip works, I looked at it, it looks like a T fitting of some sort with a hose fitted to it attached to the injector near the injector fuel pipes.

ToolmanJohn
The hose connectors at the injector have a sleeve that you pull out to allow them to be pushed onto the injector and then the sleeve is pushed down to retain the connector onto the injector stem.

 

[BobbyAus]

@CraigTAus , I have come across this same issue in my Audi Q7 3.0 TDI. I'm sure it has to do with a faulty injector. So far I have replace the hose assembly three times. And also used clamps which then cause the hose to burst. Did you find the root cause for your issue. I'm based in Melbourne Eastern suburbs (Doncaster)

 

[CraigTAus]

@BobbyAus
I think it is fixed. It has not happened for a long time now.
I think the cause was a faulty/worn injector that was bypassing a lot of fuel flow into the return line and creating a lot of back pressure, which the hose connections couldn't handle.
That injector actually 'ejected' from the engine.(injector bolt failed) Since this injector was replaced, the issue has not reoccurred.

There is a test you can do by measuring the leakage from from each injector into separate containers, with the engine running at idle.
The common return line is disconnected and clamped closed. Lengths of plastic tube connected to each injector return and run into containers. The measured amount should be the same for each injector.

 

[BobbyAus]

@BobbyAus
I think it is fixed. It has not happened for a long time now.
I think the cause was a faulty/worn injector that was bypassing a lot of fuel flow into the return line and creating a lot of back pressure, which the hose connections couldn't handle.
That injector actually 'ejected' from the engine.(injector bolt failed) Since this injector was replaced, the issue has not reoccurred.

There is a test you can do by measuring the leakage from from each injector into separate containers, with the engine running at idle.
The common return line is disconnected and clamped closed. Lengths of plastic tube connected to each injector return and run into containers. The measured amount should be the same for each injector.

Thanks @CraigTAus I will do the test and measure the fuel output for each injector.

 

[CraigTAus]

Thanks @CraigTAus I will do the test and measure the fuel output for each injector.

Bobbyaus, the VW documentation says that if one injector return volume is more than 3 times that of the lowest measured volume, then it is defective.
Only perform the test at idle, revving the engine can do damage to the injectors with the return lines disconnected.

 

[Marco333]

Hi, i recently had my fuel return line blow of jist like the original poster, as i accelerated hard on the by pass as i hit 60 mph i lost all power with a big puff of smoke from the exhaust and had to pull onto the grass verge. It turned out that 3 of my injectors were blocked causing back pressure so if anyone getting issues with their return line popping of id start by checking the injectors on the side its blowing of from. Hope this helps