changed fuel filter now hard to get started

[C6Allroad]

Because you changed the filter and did not prime the chances are that you have damaged the pump, this in turn may be pulling air in and is not pumping at the correct pressure.

Virtually no chance this would damage the pump esp as the OP said he filled the filter before starting it. From the description the seals are leaking and need replacing or re tightening.

[Crasher]

The high pressure fuel pump on the common rail 4 cylinder engines can be damaged if you don’t thoroughly prime the system in output tests and the VAG manual warns about this in quite strong terms but I don’t think the 6 cylinder pump is sensitive to it, I have had customers cars play up like the one in this post and it has always been one of my techs damaging one of the check valve seals as they easily get pinched.

[sacha35]

The high pressure fuel pump on the common rail 4 cylinder engines can be damaged if you don’t thoroughly prime the system in output tests and the VAG manual warns about this in quite strong terms but I don’t think the 6 cylinder pump is sensitive to it, I have had customers cars play up like the one in this post and it has always been one of my techs damaging one of the check valve seals as they easily get pinched.

Thanks for the info Crasher, when I used to be in the game some years back I was lead to believe that running any pump not just diesel without priming will cause damage in one way or another. the only way to get the air bubbles out back when I used to do it was to open the air bleed screw and pump away but things have moved on from then. I believe that diesel pumps these days run a higher pressure then back then and as such these pressures needed must be maintained at all times.
I hope there is no damage to the pump as things like this are expensive, but education is needed these days to be on the safe side.

[spottedhaggis]

yup, I took a closer look and was able to find the leak. That small bolt on the filter (no clue what its for) I used the bolt from the old filter without realising the washer on it had had it. Swapped it for a new one and all is well again.

[Crasher]

That is the bleed screw, you can use it to pull fuel through using a vacuum pump or the lift pump can slowly bleed out air from this port.

[spottedhaggis]

What I find strange is that for a while now every now and again I go into Limp mode and the coil light flashes, not all the time, but on and off, and sometimes I find myself in limp mode but no flashing anything, then it suddenly comes out of limp mode by itself. since changing the fuel filter and the leak, I have not gone into limp mode ones, and I run a scan tonight thinking there would be an error somewhere, but its clear.

Is it possible the fuel filter may have been clogged up a bit and could put the car into limp mode, and my changing it, and fixing the leak has resolved the issue?

[Crasher]

If it goes into limp mode it stores a code but not if it is a running defect it cannot pick up such as fuel delivery problems. If the problem has gone away, see how it goes. After 35 years of this **** I have given up asking myself why things happen.

[spottedhaggis]

lol, I must admit, I am no mechanic, I am a computer geek person, but when we had the carb 1275 mini even I was able to diagnose issues and fix them, from starter motors to electrical issues caused by rusting wires of all things.

Anyway, I constantly had the error P0046 and when cleared it would come back soon after. Now 2 days without any errors, no limp mode and no flashing coil, yet all I have done is change the fuel filter, so I can only assume perhaps there was a blockage in the old filter or something, either way my driving has not changed

[Crasher]

I keep saying to people, when I signed up for the life of a grease monkey I did not want to also be a computer and electronics specialist, thankfully I have the aptitude but some mechanics I know could't even wire up a domestic mains plug! The other thing is we don't get paid anything like what a skilled computer or electronics engineer does and now we have bloody electric cars that are going to shock us, literally! I mean, two hours to disconnect the battery, come on, what customer is going to believe that in ten years time?

[niall campbell]

I always fill up the filter with diesel before I fit on as well, just my humble opinion in doing things