Ask the Expert: Why won’t my son’s Vauxhall Corsa start when it’s warm?

Corsas can be subject to engine coolant temperature sensor failures
Corsas can be subject to engine coolant temperature sensor failures - Alamy

Dear Alex,

My son’s 2013 Vauxhall Corsa Ecoflex Energy has done 30,000 miles. After a journey it is extremely difficult to restart after a couple of minutes, such as when visiting a petrol station. It will eventually start if left for at least 20 minutes. The garage couldn’t identify the fault but fitted a new camshaft sensor and we also tried some injector cleaner, to no avail. Have you heard of similar problems with this model?
– JL

Dear JL,

I’m going to assume that, as part of its diagnostic process, your garage checked for fault codes stored in the engine’s electronic brain, the ECU, and found none. (If they haven’t, that might help!)

Corsas of this era are very sensitive to engine coolant temperature sensor failures. When these fail, they exhibit the exact same symptoms as you describe – primarily, a poor warm start, because the sensor is feeding back erroneous information to the ECU, telling it the engine is far colder than it is.

Because of that, the ECU feeds too much fuel into it, so it struggles to start. Because the ECU doesn’t deem this to be a fault – the sensor is still supplying a value that’s within the accepted range – it doesn’t flag up a fault code.

An easy way to tell if this is the issue is to check the temperature gauge while the car is running. If it shows a low value or no heat at all in the engine, even when you know the engine is warm, this is likely to be the fault. If so, the sensor costs between £10 and £20 for a brand-name aftermarket item, depending on the engine, and it’s easy to change yourself. It’s located on the left-hand end of the engine, on the top of the water pump.

Simply unplug the wiring harness, use a socket to loosen the sensor and replace it with the new one, taking care not to over-tighten it. Plug the wiring loom back in and, with a bit of luck, your problem will be solved.

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