Porque ainda ninguém postou aqui a verdadeira causa da avaria aqui vai: relé 109. Procura-o na caixa dos fusíveis - tem "109" escrito na tampa[

]. Entre outras coisas, este relé é responsável pelo corte de combustível na bomba injectora, daí dares à chave e nada. Custa 20€.
Engine will not start, or engine is difficult to start:
Question: Will the engine start at all? If the engine will start occasionally, or after an extended period of cranking, go to
section 8.b.2 - Difficult starting. If the engine cannot be started at all, go to
section 8.b.1 - Engine will not start.
b.1 Engine will not start. Test procedure, step 1: Have the transmission in neutral (or park, if automatic transmission). Have the clutch pedal pressed completely to the floor throughout this procedure (if manual transmission). Watch the instrument cluster at the location of the "glow plug" and/or "check engine" lights. Insert the ignition key into the ignition switch, and turn it to "run" (not start). Do the "check engine" and "glow plug" indicator lights come on? If they do not, go to
section 8.b.1(a) - No electrical power to engine electronics. If the indicator lights come on as they do normally, continue to the next step in the test procedure, below.
Test procedure, step 2: Wait for the "glow plug" indicator to turn off, then turn the key to "start". Does the engine rotate ("crank", "try to start", "make noise")? If it does, go to
section 8.b.1(b) - Engine cranks but does not start. If the starter motor does not operate, go to
section 8.b.1(c) - Starter motor does not operate.
b.1(a) - No electrical power to engine electronics.
PRECAUTION: Problems listed in this section can NOT be identified by the vehicle's "on board diagnostics" system. They will typically NOT set any "trouble codes" in the ECU.
- Are all other electrical systems (such as lighting systems) "dead", in addition to the electronics? If so, the battery may be completely discharged. It will be necessary to remove the battery from the vehicle and have it recharged out of the vehicle, and replaced with a new one if the battery is found to be faulty. AVOID "BOOSTER / JUMPER STARTING" ANY LATE MODEL VEHICLE (not just this one). THE ELECTRONICS ARE VERY, VERY EXPENSIVE TO REPLACE IF YOU "FRY" SOMETHING.
- If all other electrical systems are also weak or dead but the battery is good, the problem may involve a corroded or loose battery cable connection. Check the connections at the battery terminals as well as at the ground straps and chassis ground connections (these are located near or under the battery on most models). It will be necessary to make the connection good (e.g. by sanding the contact surfaces) and re-install the connection, coating it with a suitable dielectric grease to prevent further corrosion. HINT: At the battery cables, before securing the clamp nut, place a socket centered over the battery terminal and large enough to fit around the outside of the battery post but securely flat on the terminal, then tap the socket lightly with a hammer to "seat" the terminal before securing the clamp nut.
- "Relay 109" failure - this is the relay which provides power to all of the engine electronics. Failure of this relay will NOT typically set any "trouble codes" in the ECU. The only method of isolating the problem is to replace the relay. Refer to Section 7.j of this FAQ for replacement procedure.
http://tdiclub.com/TDIFAQ/TDiFAQ-8.html#b