Ask Our Experts
We show you how to track down a lost spark, plus more wisdom from the PC agony aunts.
QI just can’t get my Vauxhall Viva to start up. It hasn’t moved since last autumn and now I can’t get a spark. Can you help me? Ken Broadstairs, Stevenage
Ed says
AHere’s a guide for any older classic. Charge the battery. Remove the spark plugs. Clean and gap them. Heat the electrodes with a gas blowtorch or cooker flame to drive off residual fuel and oil. Check HT leads are in the correct order. Take them off one at a time and clean them with petrol. Replace if they’re ropey or the rubber caps are split. Inspect the distributor cap for corroded contacts, missing carbon centre contact, cracks or burns. Inspect the rotor, too. Clean them. Turn the engine to close the points, turn on the ignition and flick the points which should spark, and cause the ‘click’ of a spark in the distributor cap. If they don’t, clean their contacts with a file or abrasive paper or replace them. Refit and gap to 0.4mm maximum opening as the engine is turned. If still no spark, use a test lamp with one lead earthed – it should light on the coil’s + terminal. If not, suspect a bad connection between ignition switch and coil. With the points open, the lamp should light on the – terminal, too. If not, the current is reaching earth before it gets to the points. Maybe there’s a trapped wire, or something incorrect inside the distributor: two-piece points need careful arrangement of their insulated spacers. Check that power is arriving at the distributor with the points open – if not
the coil-todistributor wire is broken. If all is well and the points still don’t spark, change the condenser.
With the points sparking, check for a strong (5mm) spark at the king HT lead. Hold it in pliers near the engine and flick the points. If not, try another HT lead, then another coil. With spark established, connect the king lead to the distributor cap. Attach a spark plug to one of the leads and check it for a spark as you crank the engine. If no spark here, the rotor is most likely at fault.
Turn the engine so the timing marks line up and check that the points are just about to open if the engine turns any further. If not, rotate the distributor until they are.
Sometimes an ailing battery turns the engine, but can’t convince it to start. Don’t waste time cranking fruitlessly. If in doubt, borrow a better one for the afternoon.