Troubleshooting

I know very little about engines. When my car won't start, I haven't a clue what to do, where to look or what to try. It's depressing and you feel helpless

This is hopefully going to be a reference for things to try when your car is broken or won't start. It should provide a valuable starting place when you get that sinking feeling in your stomach and the search function is not helping.

It will no doubt become full of anecdotal advice, some of which may be contradictory or may not be relevant to your particular model. If you want to add to it, please keep to SOLUTIONS THAT HAVE WORKED rather than conjecture. That way it should cut down on arguments or deletions.

I'll start with a couple of my own soon but i'm not yet sure how to create subcategories. Feel free to edit, but consider it work in progress. If you know how to create subcategories under the main category of "Troubleshooting", please do it and save time. Thanks :-)

Car Won't Start

Absolutley nothing happens when key is turned (if you know solution, please edit this paragraph and supply an answer) Battery flat, I expect.

Clicking noise when ignition is turned - Some charge in the battery, but not enough. Charge battery or maybe jumpstart. Don't do what I did and try to jumpstart it from a 1.2l Diesel Corsa. It won't work.

Dash lights up but that's it did you hear the whirr of the fuel pump? if not, it could be one of the following reasons:

Fuel pump knackered - Apparently this is relatively uncommon but can happen. (can anyone who's had this happen edit this and explain how it was solved please)

Fuel pump fuse has blown (located in the boot on S1s) - Look in the passenger side of the boot and you'll find a black plastic circle. remove this and fiddle around inside until you can grab fuse. pliers are handy. 20A yellow fuse.

Problem with wiring - By the passenger seat (S1) is a small, metal, circular inspection cover. Remove this and someone handy with a multimeter can check if the fuel pump is drawing any current when ignition is turned. May help eliminate a problem, if not identify it.

Inertia switch has triggered - this is in the engine compartment (S1) and triggers in the case of an accident so that the fuel is cut off and reduces the risk of fire. it can be pressed to reset. It's like a big rubber button facing skywards, near the MFRU box.

MFRU (Multifunction Relay Unit) - this is a plastic box toward the rear of the engine compartment. It has a couple of big square plastic connectors and lots of wire going into it. I got water in mine after a particularly wet weekend. Had the symptoms described above. Drying the box helped restart the car but it went again. Replacing the box (circa £40) solved the problem.

Starter Motor turns but the engine won't catch Has it rained heavily recently? Due to the engine cover having vents/holes in it (thereby making it unsuitable as a 'cover'), water can get to various places quite easily.