2.5 Tdi Hard to start - 2005 Allroad

[seventh-heaven]

Looking at my sisters Allroad as it has become progressively harder to start over the last couple of weeks. It has all the symptoms of allowing air in the fuel as it gets worse the longer it is left and once running it runs fine.

From looking around this and other forums it appears that this is not an uncommon problem with the following the possible suspects:

1. Leak in a fuel pipe around engine;
2. Non-return Valve in top of fuel filter;
3. Fuel filter itself (changed a couple of days ago by local garage to try and solve problem);
4. Fuel lift pump (is there one on the 2005 Allroad?); or
5. Main fuel pump.

Please contribute if you believe there is anything else, but I have 2 specific questions if anyone can contribute:

• Does the 2005 Allroad have a fuel lift pump? I know on the earlier models that the pump in the tank is purely to move fuel between the compartments in the tank but some places seem to suggest that a fuel lift pump was fitted after about 2003.
• Any suggested ways of testing the main fuel pump without removing and sending to a specialist? Has anyone diagnosed problems with a Vacuum gauge?

I will of course also start with a VAG-COM download but don't expect to find anything as local garage already did a simple download.

Thanks

[kite]

Have the battery tested to make sure its good. Engine won't fire until a certain cranking speed is met.
Try disconnecting the coolant temperature sensor and see if it starts any easier.

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[ceilidhalfie]

Had this issue on my 2002 Allroad after I had incorrectly fitted new fuel filter (had crimped the little o-ring which allowed air in and the fuel to drain back into the tank). However hard to start only manifested itself after a couple of days when car was unused. Used daily, it would start (maybe somewhat hesitantly). I found the problem when I fitted an electric pump between fuel filter and fuel pump - diesel started leaking out of fuel filter.
It might be an idea to try this test - if it is lack of fuel the electric pump will get it started straight away. As you have replaced the fuel filter it is unlikely this is the problem but, under the pressure of the electric pump, the leak might just show elsewhere.

[Lukenkarl]

Checked the glow plugs? I know they don't really need them but if there's a couple down...could be ?

[PaulF2.5TDi]

The return pipes on the injectors often split on the ends where the fit over the little couplings. This allows fuel to drain back and lets in air.

It's always worth checking the pump timing once up and running - it may have been on the edge of spec and a slight shift put it over.

[bluezie]

It won't be the glow plugs, my AKE engine starts instantly and runs smoke free down to about -10 degrees. All 6 glow plugs have been open circuit for years.
2005 models should have a lift pump, this might be able to be tested with VCDS in 'output tests', if not, the relay might be able to be bypassed with a link. Injector leak-off pipes are probably the main culprit for air ingress, then the seal on the thermo valve on the fuel filter.
Have you tried revving the engine and looking for air bubbles in the clear fuel pipe near the injection pump?

[seventh-heaven]

So far established that the lift pump is running when the engine is running but does only operates for less than a second on cranking. Probably not the issue but does not seem quite right. Swapped the non-return valve on the top of the fuel filter with one from a known good engine with no improvement.

Thanks for the thoughts on battery and glow plugs but it is clearly not those. The battery is incredible - I am amazed that I have been able to crank the engine over so much without it suffering, and the glow plugs are pretty irrelevant at current temps. The other 2.5tdi we have has several glow plugs not working and starts fine even in very cold weather.

I will double check the timing next although there is no reason it should have shifted - nothing has been done recently, and then try and test the various fuel pipes with a vac gauge. After that I think it is pointing at the fuel pump so it will have to come out to go away for testing which I could do without!

The only extra bit of info is that it appeared to first occur the first morning after filling with fuel - probably not relevant but just in case it jogs someones thoughts.

Thanks

[seventh-heaven]

Have come to the conclusion that it has to be the pump! So it will be coming off tomorrow to go for testing. Before I take it off do I need any of the info in the current pump to enable the coding of the new pump?

I have read the article on Ross-Tech Wicki on changing the pump on Immo III fitted vehicles but it does not make sense to me. It talks about reading the PIN from the engine ECU in the "Extra Field" and that the PIN is the 2nd 14-digit code in the field. Then it goes on to talk about a PIN to login to the ECU and it being a 4 digit pin that needs a 0 adding to the front and then another 4 digit pin to programme in. So how does that relate to the 14 digit PIN and where does the login PIN come from?

Thanks

[hanny77]

Hi Andy.

I had the same problem, but took it to an Audi specialist to sort, so my knowledge of the matter is second hand at best. But, as I understood it, the PIN comes from the ECU and you will need an auto locksmith to obtain it. It is not something accessible using the VAGCOM software.

Hope this helps.

Simon

[seventh-heaven]

Thanks - as I suspected! I think I have found the kit required to do it but it is mega bucks for just one job!

I recall there being a member based somewhere in North London who did this sort of thing. If still around is Northampton too far!? (45 - 60 mins up M1)

Thanks