A4 b6 1.9tdi hot start judder at 90 degress

[Matt109856]

Hello all, right so I could do with a little help. My 1.9 tdi auto, has an issue where it will not start when at full running temp. Starts fine if below 90 degrees temp. Juddering and not starting when at 90. Sometimes it will but 99.9% of the time it won't. I have changed the temperature sensor and thats about it.

Thanks

[Crasher]

Disregard what the temperature gauge says, when it is working correctly it is meaningless and when giving a false reading, misleading. The first step is to have a fault code read carried out and deal with whatever comes up and at the same time, have the (injection disabled) cranking RPM analysed and this MUST exceed 280rpm.

[Matt109856]

Thank you for the reply, I will have it checked, so I need to have the crank speed disabled? I saw a load of stuff that said about changing the starter motor on a forum, but didn't believe it.

[Crasher]

Disconnecting the crank speed sensor G28 would mean the test did not work as it is the output of this sensor you are interested in, the preferred way is to disconnect the injector harness from the head but this will store a fault code which must be deleted after the test. When viewing the G28 output in measuring blocks, VCDS will take a few seconds to reconnect to the ECU so sometimes you have to keep cranking for 30 seconds or more to get a stable reading.