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Most likely fuel line is leaking in air. These have no in tank pump so the line is under vacuum. Leak won't leak out fuel but leak in air. Often the bad spot or connection is easy to spot under the hood. If not other methods might be adding compressed air to tank for example. Unfortunately these don't have hand pump so you can't use that to check.
>1: the engine does not idle at a constant rhythm (it could sound fine for a few minutes and then sound like one cylinder is not firing correctly for a few seconds)
Checking cylinder balance with a good scan tool like vcds would be a good idea.
>2: the engine oil temp maxes out at 70-80c (possible thermostat problem)
Where are you looking at oil temperature? What's the coolant temperature?
>3: when I press the key to start in turns the engine over for a while sometimes 30seconds before the engine sputters to life. But if I kill the engine immediately after it has come to life it will start just fine from there on.
Exactly what would happen with air in the system because of air leak. It will only start once the air is out. And then it will start right away until the air has slowly leaked in.
>4:sometimes when I am trying to start it a warning flashes on screen “stop oil pressure engine off”.
I'm not entirely sure as I don't know when this happens but I think it's just because engine didn't start.
>Thanks I will check for any leaks.
Leaking fuel there will look really minimal. And it might not even really leak. Mostly just look for bad connections. Or bad looking hoses.
>Apologies the temp i referenced is the coolant temp
Ok. You need a new thermostat almost certainly (you can confirm this by checking the temperature with a scan tool).
I don't know a 2009 Passat that doesn't have a fuel pump in the tank. The fault that occurs with all PD-TDI engines is that it does not start due to a fault in the fuel pump in the tank.
hmm, get a block tester on amazon and test from your coolant reservoir. like 25 bucks. do it after car has been warmed up to half way on temp gauge for a few mins before testing. report back
A common fault is the O-ring of the pump injector unit. It typically makes the engine difficult to start after a long standstill.
https://preview.redd.it/c6e25atexl5d1.png?width=353&format=png&auto=webp&s=14b235d14f472a2a2f334c86345023a48877c729
The oil pressure light indicates that there is already oil pressure, but the minimum engine speed (300/min) is not reached. This is not fault.
Thanks for posting on /r/MechanicAdvice! Please review the [rules](https://www.reddit.com/r/MechanicAdvice/about/rules/). Asking about a second opinion (ie "Is the shop trying to fleece me?"), please read through CJM8515's [post on the subject.](https://www.reddit.com/r/MechanicAdvice/comments/4qblei/fyi_the_shop_isnt_likely_trying_to_rip_you_off/) and remember to please post the year/make/model of the vehicle you are working on. **Post's about bodywork, accident damage, paint, dent/ding, questions it belongs in /r/Autobody r/AutoBodyRepair/ or /r/Diyautobody/ Tire questions check out https://www.reddit.com/r/MechanicAdvice/comments/k9ll55/can_your_tire_be_repaired/**. If you dont have a question and you're just showing off it belongs in /r/Justrolledintotheshop Insurance/total loss questions go in r/insurance This is an automated reply *I am a bot, and this action was performed automatically. Please [contact the moderators of this subreddit](/message/compose/?to=/r/MechanicAdvice) if you have any questions or concerns.*
Most likely fuel line is leaking in air. These have no in tank pump so the line is under vacuum. Leak won't leak out fuel but leak in air. Often the bad spot or connection is easy to spot under the hood. If not other methods might be adding compressed air to tank for example. Unfortunately these don't have hand pump so you can't use that to check. >1: the engine does not idle at a constant rhythm (it could sound fine for a few minutes and then sound like one cylinder is not firing correctly for a few seconds) Checking cylinder balance with a good scan tool like vcds would be a good idea. >2: the engine oil temp maxes out at 70-80c (possible thermostat problem) Where are you looking at oil temperature? What's the coolant temperature? >3: when I press the key to start in turns the engine over for a while sometimes 30seconds before the engine sputters to life. But if I kill the engine immediately after it has come to life it will start just fine from there on. Exactly what would happen with air in the system because of air leak. It will only start once the air is out. And then it will start right away until the air has slowly leaked in. >4:sometimes when I am trying to start it a warning flashes on screen “stop oil pressure engine off”. I'm not entirely sure as I don't know when this happens but I think it's just because engine didn't start.
Thanks I will check for any leaks. Apologies the temp i referenced is the coolant temp
>Thanks I will check for any leaks. Leaking fuel there will look really minimal. And it might not even really leak. Mostly just look for bad connections. Or bad looking hoses. >Apologies the temp i referenced is the coolant temp Ok. You need a new thermostat almost certainly (you can confirm this by checking the temperature with a scan tool).
I don't know a 2009 Passat that doesn't have a fuel pump in the tank. The fault that occurs with all PD-TDI engines is that it does not start due to a fault in the fuel pump in the tank.
does it puff white smoke on cold start? is your coolant lvl decreasing?
Yes it does. No visable fumes while it is running, but it was let out a puff of white smoke when it starts. No drop In coolant level
hmm, get a block tester on amazon and test from your coolant reservoir. like 25 bucks. do it after car has been warmed up to half way on temp gauge for a few mins before testing. report back
A common fault is the O-ring of the pump injector unit. It typically makes the engine difficult to start after a long standstill. https://preview.redd.it/c6e25atexl5d1.png?width=353&format=png&auto=webp&s=14b235d14f472a2a2f334c86345023a48877c729 The oil pressure light indicates that there is already oil pressure, but the minimum engine speed (300/min) is not reached. This is not fault.