Leak off test, unexpected results

[Upex]

Well, just went to do a leak down test to see if issues could be injector related, and when started the car, diesel was pissing out of the leak back line I'd removed. Had to stop the car obviously so no result of test, just wasted half a litre of diesel lol.

Is this normal, as didnt think the leak back line would be under pressure?

If normal, how do I stop the return line from dumping fuel everywhere whilst I complete the leak off test?

Thanks,

[Martin H]

Return line? Do you mean the line from the fuel rail back to the filter or the 3mm leak off return line?

[Upex]

The leak off lines?

They run across very top with r type retaining clips and little push in plastic adapter. End one (rear clinder) is 90 reg blocker, others are t type joints.

[Horizon]

https://www.google.co.uk/url?sa=t&sourc ... nMWtO2Bzyw

[Upex]

Thanks horizon, I actually watched that, amongst others, before doing the test. He doesn't seem to mention, or show, that he has plugged or sealed the standard leak back lines, and doesn't react as if they pouring diesel everywhere, so not sure I can learn much from this vid.

I wonder if I need to clamp the standard leak pipe, as found one reference online to that, on a ranger rover site which use same bmw engines? If so, then appears correct that there pressure in the leak back lines, but strange I can't find much mention of needing to clamp the line off, especially considering the volume of diy leak back jobs detailed.

[Horizon]

[quote="Upex"]
Thanks horizon, I actually watched that, amongst others, before doing the test. He doesn't seem to mention, or show, that he has plugged or sealed the standard leak back lines, and doesn't react as if they pouring diesel everywhere, so not sure I can learn much from this vid.

I wonder if I need to clamp the standard leak pipe, as found one reference online to that, on a ranger rover site which use same bmw engines? If so, then appears correct that there pressure in the leak back lines, but strange I can't find much mention of needing to clamp the line off, especially considering the volume of diy leak back jobs detailed.
[/quote]

You will have to clamp/ plug off the original leak off pipe. If you look at the diagram on the link I posted yesterday the leak off pipe and the return pipe from the rail pressure control valve are all tee'd in together, so when the common rail PRV valve opens to return fuel to the tank it will flood out of the disconnected leak off pipe.

[Upex]

Thanks horizon. I'll clamp the pipe next time then lol.

Not sure what diag what you mean, as link open a YouTube did for me? But think I saw what you mean in realoem

[Horizon]

http://www.yildiz.edu.tr/~sandalci/ders ... aining.pdf

I was meaning the blue marked lines/pipes in the first drawing, when the line from the injector return pipe is taken off, any fuel being returned to the tank from the high pressure fuel pump ,when the pressure regulator valve is opened will gush out of it instead of returning to the tank, as in the diagram they are all tee'd together. Hope this makes sense.

[Upex]

Yeah, sorry horizon, I thought you meant the vid lol.

I see now, and realism shows it's connected to pump as well, so it is normal thankfully, I'll just have to pinch it off.

Good to know it's normal, but bit gutted as thought it may have been pointing go an issue that could have led to a fix of my power loss lol.

Cheers bud, I owe you a beer or three by now lol

[Upex]

So, finally done leak down/back/off test and results of 1 min at idle are:



Left most is front injector (cylinder 1?) And right pot is the rear injector (6?)

Opinions please....

[Horizon]

Found this youtube video showing a leak off test, his duff injector virtually filled the test pot in 30 seconds. !
https://www.google.co.uk/url?sa=t&sourc ... s4OloyaIiQ

[Alan Gunn]

Look's like a bit too much out of all of them to me but could be wrong.
I used to work from the rule of :
3 mins of tickover = 35ml leakoff max per injector.
But i am no diesel expert i was just a general mechanic before retiring so old school.

[Upex]

Think old school will out this time Alan, as no codes to help lol.

I've read so many different approaches, 2/50ml in a min the norm, some measured at idle, others via a idle and blip method, others say volumes doesnt matter, its vatiance between cylinders, some say 10% others 20% ok etc, I haven't a clue what's right wrong good or bad.

Argghhhh