Vauxhall Astra issue starting

[Liuokwe]

Hi,

I had an issue the other day with my 2002 mk4 Vauxhall Astra 16V petrol. Its an old car but not let me down so far, only 63k miles. The other day I went to leave for work and it wouldn't start. It was reasonably cold overnight after some hot spells but nothing drastic as only in UK, not the arctic! It was turning over such that I know it wasn't a battery problem (replaced in the last year).

I noticed the coolant light (rectangular box with 5 pointed star) was lit. Whether this is just a standard ignition light or not I dont know. I checked the manual and added some tap water (750ml?) to the tank and then after some persuasion it eventually started. About 30 seconds of a little white smoke from exhaust and then drove for 20 minutes and it was fine. This was on saturday (4 days ago) and it has been started and driven each day since with no problems at all (started first time, no smoke, no lights). Its booked into the garage as I must have messed up the coolant concentration with just water so he'll fix that. Tbh i'm not even sure if that was the problem to begin with.

I'm aware that the coolant is a closed system so is it perhaps a leak? I also know white smoke is rarely good but it wasnt for too long and not happened since. Also, shouldn't an engine start even with low coolant? Its the not starting and then starting after a while that puzzles me.

Anyway I will get the guy to give it a look over, just wondered if anyones ever had a similar sounding issue?

Cheers

[Penelope Stopit]

Only a hunch but........

There is a possibility that the engine ECU temperature sensor was not immersed in water and if this was the case it would not send a true temperature reading to the ECU, the reading would have shown as warmer and the ECU would have supplied the injectors with a signal for a warmer engine, the engine would have then not been getting enough fuel to start from cold

A faulty engine ECU temperature sensor could also cause the same problem

[GreenV8S]

I wouldn't expect low coolant level to prevent the engine from starting. I guess it's possible the ECU has some protection logic along those lines, but I've never seen it. More likely the low coolant alarm and starting problems are unrelated.

Adding half a liter or so of water to the system won't make any great difference to the condition of the coolant and I wouldn't see that as a problem, but if it's losing coolant then obviously you need to fix that.

If the engine won't start, one of the best things you can do it just walk away and leave it for ten minutes. It lets any excess fuel evaporate, and lets the battery recover a little. It may be you simply had some other minor problem such as damp electrics or a weak spark, unrelated to the coolant level.

The white smoke was probably just unburnt fuel from your failed attempts to start the engine.

If the ECU was over fueling for some reason and flooding the engine, on many cars you can clear this by opening the throttle fully to engage 'flood clear mode' which cuts off the fuel, while you crank the engine for 10 - 20 seconds. You may find it shows some signs of life as the excess petrol clears, but you'd need to close the throttle afterwards and start it normally to get it running. If you see that behaviour, it supports the theory that the problem is causing over fueling.

These engine temperature sensors are usually thermistors, which show increased resistance at lower temperatures. If you have a broken wire, bad connection or faulty sensor, that will often show as a very high resistance, which the ECU interprets as very cold. If flooding becomes a recurring problem, that's the sort of fault I'd look for.

Edited by GreenV8S on Wednesday 2nd September 11:30