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Matt
Matt, Mechanical Engineer
Category: Audi
Satisfied Customers: 22160
Experience:  BEng hons Mech engineering, in auto industry 22 years
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My old A4 year 2000 has started acting up sometimes it will

Resolved Question:

My old A4 year 2000 has started acting up sometimes it will not start and a couple of times it has started and there is nothing on the accelerator, but after a little while it is back to normal starts every time. It has just been standing for 3 weeks and it started first time. Any ideas?
Submitted: 1 month ago.
Category: Audi
Expert:  Matt replied 1 month ago.

hello

can you tell me what engine size and fuel type this is please?

also how many miles are on the car and when it was last serviced?

Customer: replied 1 month ago.
Petrol. 1800.172000 miles About 3 months ago.
Expert:  Matt replied 1 month ago.

Hello

This sounds like a lack of fuel and could be a lack of fuel pressure from the electrical pump at the tank.
1st thing to try is to remove the fuel filler cap and then flick the ignition on whilst listening for the brief ‘buzz’ of the pump

If the connections to the pump are corroded or damaged then the pump could stop at any time or could not be running at full speed. Check that its relay switches in and out and the relay contacts are clean and bright – replace the relay if in any doubt and do the same for the fuse,
Ideally measure the pressure at the injector rail (should usually be around 3Bar / 45psi +) and if this is low check the pump as described and also consider changing the fuel filter as if this partially blocked this too will reduce pressure.

You can also get this issue with contaminated fuel , if there’s water or dirt in the tank then either the petrol floats on top of the water or the filter sock on the pump is choked up – so if the other things check out then I’d consider pulling out the fuel pump and cleaning the filter sock

And one other thing to try is to loosen off the fuel filler cap, as there’s a 1 way valve built into the cap to let air into the tank and so prevent a vacuum from being created as the fuel leaves the tank to the engine
If this helps then replace the cap with a new item

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