After experiencing a very long saga of trying to get my 6 to start, I’ve spent hours trawling through the last decades worth of posts trying to find answers that would help - as I’m sure you’ll all agree there have been lots of posts about non starting and so many knowledgeable responses.
I thought it would be massively helpful to try and compile a list of checks that anyone can try even if you are an amateur like me - Thank you in advance to you all who have provided these answers over the years.
These checks are based on knowing you’ve not been messing with anything since it last started ok!
So firstly, if your car won’t start the first check is to see if it’ll crank or not;
If it won’t the best things to check are your;
1. Battery - Is is trying to turn over or just clicking when turning the key? Ensure it’s charged up, connected tight and giving at least 12.4 volts.
2. Starter Motor - If your battery is good but still no crank, you can try giving it a GENTLE tap with a long screwdriver and hammer. (If your starter motor needs replacing it’ll be a manifold off job - if you search ‘Replacing inlet manifold gasket’ there is a good faq showing how to get this off and access to the starter motor for replacement. But also worth just checking the wiring based on some peoples experiences!
3. Earths! - Earthing issues can prevent it cranking - there are a number to check including on the gearbox and behind the passenger headlight under the battery tray. You can always try running a jump lead from your negative to the block to test!
Secondly, it cranks but no start (potentially not firing either);
1. Check that battery again (See above) - so many posts resulted in a knackered battery!
2. Crank Shaft Position Sensor - a vital part of the starting process, if this is knackered it won’t start and they either work or they don’t - It’s a brown sensor that has a single bolt onto the gearbox, you can try doing electrical tests but a replacement is cheap enough from a factors/eBay.
3. Fuel Pump / Fuel Pump Relay - does your fuel pump prime when you turn the key? If not your pump may be knackered but equally it could be your dual relay which is bolted to the back of your battery box - search ‘Fuel Pump Relay FAQ’ and ‘Fuel Pump FAQ’ for specifics but as for the relay if you can get a spare from a breakers with 240107 on it then it’ll do the job! (Also used in 206, 207, 307 and 308 to name a few so quite common!)
4. Fuel Cutoff Switch - if you aren’t getting any fuel, just check the ‘big’ red button in the engine bay hasn’t been pressed! Also make sure you actually have enough fuel as well of course.
5. Camshaft Position Sensor - the blue sensor found on the left hand side of the engine by the cam belt - not as common to fail but worth a check!
6. Central Locking Fuse (Fuse 4 or 6) - this fuse can go which can prevent starting it’s a 5amp fuse which will also wipe out the central locking as well.
7. Spark Plugs/Ignition Coils - Faulty/Dirty plugs or faulty coils whilst uncommon with starting issues can of course prevent the car from continuing to run or idle so this a good check!
8. Your Key - make sure that the little black chip is in your key as without it, your immobiliser won’t disengage. (My chip actually went faulty and needed recoding!)
There are of course other reasons that can cause no starting such as bad timing, low compression, ecu etc but that’s quite advanced for many and would be a job for a garage in many cases I imagine?!
I’m sorry that I’ve probably not covered it all but I hope it’ll be worthy of an FAQ perhaps if not after some other input from you lot?