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Matt
Matt, Mechanical Engineer
Category: Car
Satisfied Customers: 21610
Experience:  BEng hons Mech engineering, in auto industry 22 years
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Vw Passat 2012 170 20 tdi . Won't start, sometimes does then

Customer Question

Vw Passat 2012 170 20 tdi . Won't start, sometimes does then dies out. Esc fault on dash.
Submitted: 1 year ago.
Category: Car
Expert:  Matt replied 1 year ago.
Hello If you can you tell me what fault codes you have I'll try and provide a more specific diagnosis but its worth checking that the electric pump that feeds the main fuel pump is working correctly, it should run for a few seconds then switch off when you first turn the ignition on. If the connections to this are corroded or damaged then the pump could stop at any time. 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 voltage at the pump and check its getting 12VAlso if its not injecting at all then check the connections to the crankshaft sensor, unplug it and check for corroded contacts and broken wiring, and consider fitting a new sensor - do the same for the cam position sensorIf the EGR valve is stuck open then this too can effect starting so try disconnecting it to see if this helps or changes anythingCould also be an injector leaking fuel back through the overspill pipe, so not getting enough fuel pressure to tell ECU to fire the injectors, this is trickier to find and you’ll need the garage to do a ‘run back’ test to identify which one is the issueLastly it’s also worth considering fitting a new fuel filter as if only slightly blocked this can lower fuel supply pressure and choke the main pump, the pump will be more sensitive to this when its cold as diesel thickens considerably with low temperatures.
Expert:  Matt replied 1 year ago.
Hi
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