VW Polo Diesel Won't Start Despite Turning Starter

Had exactly the same issue with my VW Golf TDI 2003. Same symptoms, engine would crank but not start, plus the check engine light stayed on. I have some experience working on cars but this one had me stumped. First thought it was an ECU issue too, but after taking it to the workshop they discovered the battery cable connections were corroded and loose. The poor connection was causing voltage drops which confused the engine diagnostics system, triggering the check engine light and preventing proper startup. The fix was surprisingly simple, they cleaned the battery terminals, replaced the cable connectors, and properly secured everything. Total cost was 155€ including labor. After that, the engine started right up and the warning light disappeared. Before you spend money on complex ECU diagnostics, might be worth checking your battery connections. Engine stalling and starting issues often trace back to electrical problems. What exact engine variant does your Polo have? Also, have you noticed any other electrical issues lately, like dimming lights or slow starter motor? These details would help determine if you are facing the same problem.

Thanks for sharing your experience. My Polo has the 1.9L diesel engine. Done some basic checks since yesterday and noticed the starter motor seems to be turning slower than usual, which matches your electrical theory. This makes a lot of sense since the engine surge and starting issues came without any prior engine fault warnings. For reference, last service was done at 132000km just 3 months ago and everything was fine then. Will check the battery connections before assuming a major ECU issue requires extensive engine diagnostics. Could save me a significant repair bill. Will update once I investigate the electrical connections, your tip about checking for corrosion seems like a good starting point.

Thanks for the update about your Polo. The slow starter motor really points toward the electrical system being the culprit, just like what happened with my Golf. When I had the issue, I initially feared the worst about ECU failure, but it turned out the electrical connections were the root cause. The fuel injection system in these engines is quite reliable, but it needs proper voltage to function. Before my battery connection fix, I also noticed the starter getting sluggish, especially during cold starts. The engine software can throw misleading fault codes when it doesnt get clean power. Since your car was recently serviced, major mechanical issues are less likely. On my Golf, cleaning the battery terminals and connections cost just a fraction of what an ECU repair would have been. The engine diagnostics showed multiple errors initially, but they all cleared up once the electrical system was sorted. A quick way to test: check if the battery terminals wiggle at all, even slight movement can cause the issues you described. Would be interested to hear what you find after inspecting the connections.

Thanks for the feedback. Just wanted to update that the electrical theory was spot on. Found significant corrosion on the negative battery terminal and the connection was quite loose. After cleaning both terminals thoroughly and securing them properly, the engine started right up and the check engine light went off. The starter motor is now spinning with normal speed and no more engine stalling issues. Total cost was just 25€ for a new battery terminal clamp and some cleaning supplies. Really relieved it wasnt an ECU failure as initially feared. This experience taught me to always check the simple things first before assuming major engine fault scenarios. The engine diagnostics can be misleading when the electrical system isnt delivering consistent power. Will definitely keep a closer eye on battery maintenance going forward. Thanks again for helping avoid an unnecessary and expensive workshop visit for what turned out to be basic electrical maintenance.