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Has anyone carried out a diesel purge on a 1.2tdi polo ?

 

I set up to do a diesel purge on the Polo (1.2tdi 6r 2013 model bluemotion) as its got 105k on it and is a bit lumpy at low revs and has a bit of a diesel knock.

Anyway,  I rigged up the supply and return lines from the high pressure fuel pump to the purge liquid container and looped the supply and return from the fuel lift pump pump together as I have done on a few cars before . Then tried to start it and it wouldn't,  it just kept turning over without starting. So I tried again, ensuring that everything was primed but still no good. Hmmm.... As soon as I reconnected the pipes back it to standard it started up literally instantly so there must be I suspect a pressure sensor on the fuel pump or supply that signals that there is pressure in the supply line...Any ideas?  

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Sorry for the slow answer, I read this a couple of times and didn't quite follow what you were trying to do.    I tend to do what nige said, empty the filter housing and fill it with injecto

Thanks for the replies all. I have a solution.... As you rightly say  the system has a fuel  pressure switch to prevent the engine running with little or no pressure,  although it will turn over

Look at your V5 logbook and the engine serial number will be a set of letters and numbers, the letters are the engine code

CFWA engine code?

If so, G247 fuel pressure sender sounds like a candidate; not sure where it is located though.

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Thanks , unsure of which is the engine code, looks like from the book it is 55fTdiM5f  it's a 2013 6R model

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nige8021

Look at your V5 logbook and the engine serial number will be a set of letters and numbers, the letters are the engine code

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Ok thanks it's a CFWA.

Tried again with the purge, raising up the hoses a metre to give it a bit if pressure but still no start (engine turns over) reconnected hoses and started instantly...dont want to override the pressure switch on the fuel pump in case I damage anything...surely some one else has diesel purged a 1.2tdi ?

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nige8021

Looking at the schematic diagram of the fuel system, the HP engine pump will be looking for a pressurised fuel supply from the in tank pump of 4.5bar.

 

The way I used the Molly purge on my Octavia & Touareg as suggested by @Yeti was when I replaced the fuel filter,  filled the filter bowl with the purge and then fitted the new filter and started the engine as normal

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Sorry for the slow answer, I read this a couple of times and didn't quite follow what you were trying to do. 

 

I tend to do what nige said, empty the filter housing and fill it with injector cleaner or purge, (even paraffin in the old days). I tend to use Forte, just because it's what I've always used and nothing's broken from it yet. Then go for a blast down the road. 

 

My normal way of doing it is:

Take the breather off the top of the filter housing (fragile plastic thing with the R-clip)

If it's got a drain down cap on the bottom of the housing, use this to run the fuel that's in there off into a clear container.

Inspect fuel for foreign materials and water contamination.

Carefully take the cap off the filter housing (those tiny bolts love to snap).

Remove the filter

Clean the inside of the housing and use a light to check it for holes.

Fit a new filter.

Check the cap for damage (they corrode slowly from the outside), same for the fuel lines.

Refit the cap.

Fill the filter bowl to the with your choice of cleaner through the breather hole. I use that so I can totally brim it. Let it settle, and refill as it soaks through the filter.

Check the breather for damage, refit it and the R-clip.

Start it up with your foot on the pedal, just in case it's pulled air in to the lines while it's been apart, and go for a blast. 

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  • 2 weeks later...

Thanks for the replies all. I have a solution....

As you rightly say  the system has a fuel  pressure switch to prevent the engine running with little or no pressure,  although it will turn over on the starter motor it won't start.

So this is what I did to achieve a recirculating moly diesel purge :-

1.disconnected supply and return from fuel pump and attached them together.

2.filled a glass jar of liquid moly diesel purge 

3.attached a return line hose to the jar

4.attached a supply hose with in line filter to the jar AND put in a hand pump primer bulb that I took off my boat and primed the line and pressurised constantly,  the engine started and the recirculating flush worked, I just had to keep pumping the hand primer bulb to maintain the pressure...a bit tiring but worth it. 

So all good. Hope this helps others out

thanks 

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Seems a bit of a long way round versus using the filter bowl as a reservoir and letting the sealed system pressurise itself, but if it works, it works.

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