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Trouble starting Lupo in hot weather

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Hey all, 

I have a 1.4 automatic Lupo, 2000 which has trouble starting in hot weather. On cooler days I have no problems, but on hot days, particularly when my car is in direct sunlight it struggles to start. It just cranks and cranks but struggles to fire. Sometimes it takes 10 tries before it starts, other times only a couple. Weirdly this rarely happens when I start the car for the first time in the day, only when it has been driven around and the engine has been switched off (so I'll park up, pop in the shop, come back and it struggles to start). Luckily it has always started eventually, but I know it's just going to get worse. Any ideas what it might be? After reading on here about it possibly needing a new crank sensor, I took my car to a mechanic who said if it was the crank sensor I wouldn't only have this problem in hot weather? I also ruled out it being a problem with the immobiliser as I have the same problem with my spare key. I'm thinking about buying a diagnostics tool myself to find out what the problem is rather than taking it to the garage to diagnose. I have read on this forum about vagcom? But have no idea where to start! 

Thanks! :)

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Probably a fuelling problem. Vapour lock due to clogged fuel filter. Maybe? Could be a dodgy coil pack. Sniff the exhaust when cranking and hot... you shoukd smell raw fuel if ignition (coil pack) problem. If no fuel smell, then fuel problem.

oh, don't forget to change both fluids in your auto box next service. Everyone fogets!

Edited by mk2

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Get codes read with vcds, you can get cheap £5 VAG KKL leads off ebay if you have a spare laptop.

Flakey crank and cam sensors can play up when hot, but codes would point you there, no point guessing and buying bits you dont need.

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Thanks guys 😁

I don't know where to start when it comes to vag leads. So if I buy one off ebay, do I need to download some software for my laptop? If so which software? Any links? 

Sorry I'm a complete beginner and a fairly new driver 🙈

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If you’re in the Lincolnshire area I’ve got a scanner.

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Plus I’ve said it before and I’ll no doubt say it again - don’t rule out a dicky starter motor. When cold, like being left over night, it’l behave, but get some serious temperature through it, like after being sat next to a warm engine and if it’s old and tired the electrical wizardry inside the solenoid can start to get very lazy. Extreme temperatures do wierd things to electrical resistance.

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g28 speed sensor?

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That wouldn't stop it starting? Or would it...? Does the 1.4 have a cam ref sensor (to get the four stroking sequencing right)?

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g28 causes some funny issues and doesn't always throw a code.

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If you have a laptop get £5 VAG KKL lead off ebay and run free VCDS Lite that will be good enough to get codes etc. You can choose to register it for a hefty fee or else google for the crack of you want full functionality.

There probably are ways of doing it with phones etc but I dont know them as i am happy with the laptop.

Edited by Sausage

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26 minutes ago, Sausage said:

If you have a laptop get £5 VAG KKL lead off ebay and run free VCDS Lite that will be good enough to get codes etc. You can choose to register it for a hefty fee or else google for the crack of you want full functionality.

There probably are ways of doing it with phones etc but I dont know them as i am happy with the laptop.

Thank you! I think that's exactly what I'll do 😊. Unlike cars, I'm pretty good with computers so can hopefully get the full version unlocked without paying for registration 😁. Thanks again! 

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a. Pics of yourself and lupo?

b. If you think it is the battery or to eliminate it, try jump leads and see what happens when it isn't starting.

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Had exactly these symptoms on a 1.4 Polo, could be temperature sensor which has 2 circuits; one for gauge and one for ECU. Cold starts aren't a problem as the sensors tells the ECU to richen the mix, hot starts the sensor 'sees' a cold engine and gives the ECU the wrong information and hence a poor start, this was always accompanied with a strong smell of fuel and was intermittent as the sensor didn't fail completely. The longer the engine was stopped the less likely the problem. Changed the sensor and cured the problem.

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