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Discussion Starter #1
Hi I'm new to this forum but have researched many threads plus youtube videos etc. I have a 2004 T5 2.5 (I believe it's an AXD engine) which has a problem starting first thing in the morning in cold weather. Last winter I swapped out loads of parts including relays, fuel temp sensor and even had the fuel tank out to replace the in-tank pump! Nothing solved the problem and the weather's just turned cold enough for the problem to manifest itself again. I've tried to avoid changing the glow plugs due to the access issue, however I don't think they're the problem. The symptoms are the engine cranks over fine but doesn't fire at all, not even a sputter. As the ambient temperature increases (usually while I have a coffee for an hour or so) the engine sputters a bit on cranking and I know at this point I will eventually get it started. However it fires up to about 2k revs then dies immediately (almost as if the ignition is switched off). It does this half a dozen times or more before finally staying running but I need to keep the throttle open for a minute or so before it will idle without dying. After a few minutes it will run and drive fine and no more starting issues all day until the next cold morning. To me this doesn't seem like a glow plug problem and I'm now leaning towards the fuel shut off solenoid. From what I can gather this solenoid is an integral part of the fuel pump so I'd need to change the entire pump, is this correct? I see you can buy solenoids but they all seem to be for the 1.9 engine. Has anyone experienced this specific problem and am I on the right track suspecting the solenoid? There are no fault codes showing on the VAGCOM hence why I think the solenoid is sticking shut when cold rather than there being an electrical issue. Help, suggestions or confirmation much appreciated!
 

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Does this sound like fuel starvation to anyone else?

Pin hole somewhere and the fuel is running back to the tank.
 

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Discussion Starter #3
Hi Rhys, thanks for the quick response, if this were the case then I'd expect it to have the same problem all year round, not just when the weather's cold. I'm wondering if the solenoid sticks shut when very cold.
 

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Discussion Starter #4
Hi everyone, it's fixed! The issue turned out to be the ECU. Had to send it off to ACTronics along with the instrument cluster and key - they repaired the ECU and returned it in a couple of days and problem solved, starts every time in the cold! Apparently it's a recognised fault that occurs in the Bosch ECU. If anyone wants more info, ECU model etc, then let me know. The only side effect is the idle is a bit slow and therefore lumpy until it warms up. Does anyone know if this is adjustable on the 2.5 tdi?
 

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Good to know you've got it sorted & what the cure was & for letting us all know (y)
That fault had the potential to cost a fortune replacing parts & the ECU would have most likely been the last thing to go for. Good effort !
 

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Yes brilliant, thanks for getting back. Just for info, I'm fairly sure there is no stop solenoid on a 2.5 because the ECU can simply shut the fuel off at the injectors anytime it wants. Maybe that is what was happening to yours. There isn't any cold idle adjustment possible (the ECU has control of it) If you have access to VCDS you can see if the engine coolant sensor is reporting realistic start and warmup temps. Other than that (dare I say it!) you might be back to glow plugs.
 
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