car wont start?

Hi, Graham,
Without knowing which car you have, it's a bit difficult to give you a full answer. Presumably the plugs are gapped and cleaned properly. If the gap's too wide, they won't produce a spark, as the current won't be powerful enough to jump the gap. Are the plugs new/fairly new? If they're really old, the insulation may break down and leak current to the engine block thorugh their sides. You may see a spark at the gap with the plug out put the electrode touching an earth point, but when they're back in their holes, they won't spark. Are the HT cables good and clean? The insulation on those breaks down and can arc to the engine block, so you'll lose the spark at the plug. Are the HT leads tight in the distributor cap? Take them out one at a time then replace them to make sure the connections are clean. Take out the lead from the cap to the ignition coil, check the connections are clean and shiny, then replace it. If you feel confident, take off the distributor cap and see if that's clean inside. It's generally held on with two captive screws. Make sure the brass contacts are clean inside it and the spring contact at the top is free to move. Then check the rotor arm on the distributor. Is it clean and shiny? That can short out internally and that could stop you getting a spark. Probably you have electronic ignition, so no contact breaker points to worry about. Next thing is the ignition coil. Could be bolted onto the engine or on the bulkhead at the back. Make sure the connections are clean there. There should be the main HT lead in the middle with a smaller low tension one on either side. Are they clean and tight? Having checked all that, you're left possibly with the engine management system, if your car has one. That really is a garage job or mobile mechanic. Go through all these steps from the top carefully. Generally, it's something simple. But be careful playing with these bits, as there can be a hefty voltage produced in the ignition system of modern cars when the engine's running. Do everything with the engine off. Best of luck!

Denis Langley

Denis Langley
February 2007