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Mike
Mike, Technician
Category: Audi
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I have an audi a4 2.5 TDI convertible I have had a new injector

Customer Question

I have an audi a4 2.5 TDI convertible I have had a new injector pump and new lift pump in boot, new filter and new filter valve. No diesel is leaking out of the engine or any of the pipes, the car runs fine all day and will stop and start, but leave it over night and the car will not start in the morning. There is an air bubble in the clear plastic fuel pipe they runs from the fuel filter to the injector pump. If you rock the car the fuel runs backwards towards the fuel filter and the car won't start. If you pump fuel through manually the car fires up and you can turn it off after a minute and it will fire up again straight away and run fine all day with no issues.
Submitted: 3 years ago.
Category: Audi
Expert:  Shantal-Mod replied 3 years ago.
Hello,

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Customer: replied 3 years ago.
I still require a from an expert
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Customer: replied 3 years ago.
Please continue to search for an answer
Expert:  Shantal-Mod replied 3 years ago.
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Expert:  Mike replied 3 years ago.
Hello and Welcome..

My name is MIKE - Im happy to help / advise you ...

I note you say above - no leaks... how have you checked / tested the system?

Do you have any diagnostic results at all?

Rgds, MIKE......................................
Customer: replied 3 years ago.
Garage have checked no leaks Diagnostic reports showed no faults - garage and Rac. Still the car won't start after being left standing as per the original question. Car runs perfectly once started and will stop and start all day.
Expert:  Mike replied 3 years ago.
Hello again - Thank you for your reply and further info.

Ok - its important to realise that per your question - and the description of exactly whats happened with the car- you have a leak somewhere in the fuel system..

This is proven by the fact that you can see air - and also - when you prime the system, it starts.

Its also important to know that unlike a petrol - , just because a diesel leak ( wet) cannot be seen anywhere - that doesn't mean there is not a leak.. Air can be sucked in - but no diesel leak out... and that often misleads people - even some garages.

It has to be said too that the "diagnostics" - tests etc cannot have either been done properly or completely - because the fault exists still - regardless of any "results" saying nothing is wrong. You will not get fault lights or fault codes necessarily for this sort of issue.

What needs to be done is to have proper flow rate test equipment used - and leakage test equipment fitted to the diesel system - and this between the two will find the cause of your troubles.. Too - even if such equipment is not available for some reason - a simple pressure device such as a Mityvac pump would find the cause - So one way or the other, thats what needs to be done now to sort this for you. This will find the cause - be it a seal - a fracture in the filter casing / seals ( common but hard to find without the proper tests )... or injector leak back faults etc - any of the above will mean the system is not holding pressure as a diesel needs to do to operate correctly.

I would honestly suggest that If you haven't used a Diesel Specialist - if you have one local to you , you would be best to use such a place - they have all the test equipment needed for this as above and the knowledge to sort this for... basically plug in "diagnstocs" is no good for this.

So do as above and you will have this sorted - that is the way on this one. Obviously I cannot say it "will be this / that" - other than you have an air draw somewherebut working as above, you will find it - and cure it.

Do let me know if you need anything else at all -

Kind Rgds - MIKE.

..>> >> .> .Meantime..............Please do click on the "OK/ Excellent ratings" for me as that's how Im credited for helping you - Thank you in advance for that...

You can and are most welcome to get back to me anytime you might need - clicking the OK ratings does not close you out at all..


Rgds, MIKE.