Audi A4 TDI battery...

**randall977** · 28-01-2010,11:19 PM

My brake warning light regularly comes on when starting and today the car really struggled to start. I've never had to replace an Audi / VW battery before - even on a high milage 8 year old car! My current Audi is only 4 years old with 68K. Anyhow, how much for the real deal OEM part? There's one on eBay for £90(new)...

**a8 tech** · 29-01-2010,12:12 AM

try to charge the battery firstly before anything else.Battery failure causes, if the electrics are fine then this can be a result of poor storage practise.
Sales pitch cars not being continually dripped charged can be fine at the time with a quick boost start but this reduces the life span.

**randall977** · 29-01-2010,12:15 AM

Sounds like good advice, thanks. The car doesn't get driven that much so that probably doesn't help.

**randall977** · 01-02-2010,11:53 AM

Well I charged the battery, went for a 4 hour drive - this morning it took a few attempts to start the car. Normal scenario is that the brake warning light comes on and the engine cuts out (when trying to start the car in the cold).

New battery required?

**kite** · 01-02-2010,12:02 PM

have it checked before changing it

**a8 tech** · 01-02-2010,08:59 PM

If the battery is ok then you need to check the pressure pump in the tank, common failure from contaminated oil clogging it up from the tandem pump leaking oil back into the fuel, further problems could lie in a failing egr flap.Neither will store a fault code.I presume you have checked for fault codes and found none.Its difficult to give a cause without cranking rpm and battery condition so these suggestions are speculation.

**randall977** · 01-02-2010,10:05 PM

Thanks A8tech - there are no fault codes. I am going to get the battery tested tomorrow. I believe the EGR valve was replaced not that long ago under warranty... My gut feeling is that it's not the battery as I've never had a battery give up on any German car less than 8 years old - but I hope it is the battery!

**randall977** · 02-02-2010,02:22 PM

Fault shown on two rear wheel speed sensors.... Glow plugs look like a possible culprit - below 5 degrees.

**randall977** · 02-02-2010,08:56 PM

So the battery is fine but it sounds like there could be a problem with the plugs. I also noticed driving home that the car seemed to be misfiring - a bit lurching. Is this going to be an expensive job, could I do it myself easily?

**a8 tech** · 02-02-2010,09:03 PM

Glow plugs will show a fault, I suggest you remove the fuel filter and empty into a clear container.

If there is a large oil mixture then this will indicate the tandem pump issue and further invest required.

Remove the lift pump from the tank to visually inspect, it could be blocked with oil.

The lift pump supplies the fuel to the tandem pump at approx .50 bar.

The engine will start without the assistance of the lift pump but a delay will be noticed.
When the engine is warm the holding pressure is sufficient for first time start.

Worth a look me thinks