2004 B6 S4 will not start

 
Old 06-18-2017, 04:22 AM
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Default 2004 B6 S4 will not start

hi all,

So my trusty Steve (S4 ... S for Steve ... did you see what I did there ...) is refusing to start. The engine turns over but no ignition.

About 3 weeks ago I started to notice that every now and then the car would take an extra second or so to start. Then 2 weeks ago the car wouldn't start at all so I called out the AA - they said that the battery looked old and also looked like it had been replaced with an under-spec'd battery (only 550 CCA) - after a quick jump start all was ok but the AA chap suggested the battery might be on it's way out. He did a quick test and confirmed that there was nothing draining the battery when powered down.

A week later it happened again so I had the battery replaced with an 850CCA battery and all was fine. In the last week I think I noticed once that cranking took a little longer than usual but it only happened once.

Then on Friday morning the car refused to start at all. You can hear it turning over but nothing is firing.

I've checked the Fuel Pump and Fuel Pump Relay and both are good. I even bought a replacement Fuel Pump Relay but that made no difference.
I've also checked the fuel to the rails and that's good. By 'good' what I mean is that I attached an airline to the hose that connects to the fuel pump and confirmed that there's no drop in pressure (I know, it's a subjective test but I don't have a pressure gauge to get the correct PSI ratings). The reason I used an airline is that I'm told it's now a fire-risk to hook up the pump to the fuel line due to the high-pressure. I'm guessing this is probably more likely to be an issue if the engine is hot. Anyway, the airline blew the fuel that was in the lines all over the engine bay and to the other side so I think that's fine.

One thing I did notice is that I'm only getting 7.7v supply to the Fuel Pump Relay. Which would suggest a problem prior to the relay? But then surely if the power to the pump was low then that would also prevent the fuel pump from supplying fuel to the rails?

I've run the VCDS and found a heap of faults but nothing that jumps out as being critical - mainly "low or intermittent voltage" - I don't know if they're just because the battery is getting low after 2 days' of testing fuel pump and relay (it's now on charge with a Battery Tender so I'll try again tomorrow night after work)?

Worth noting that I haven't tried starting the car yet since I last unplugged the battery so I don't know if that would wipe any codes that might be generated when trying to crank?

As I say, the battery is now on charge so I'll try to start the car again tomorrow after work and see if I get any other error codes.

I'm also going to check the passenger foot-well to see if there's any sign of water getting into the CCU.

And I still need to get into the plugs and check that they're ok.

Attached is the log file from tonight's VCDS - I've highlighted in yellow the pre-existing faults - and in red are the new faults. My comments are highlighted in blue

Any thoughts on what to try next?

Thanks in advance for your help and suggestions.

cheers,

David

p.s. I'm in New Zealand so there'll probably be a time difference between when I get home tomorrow night and crack on with the other tests and you guys in Europe and the US.
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Old 06-18-2017, 05:35 AM
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I've found a page where they guy mentions that the Speed Sensor is the same as the Crank Position Sensor. This is flagged as an intermittent fault in the VCDS log. So maybe need to add that to my list of things to check tomorrow night ...
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