Generally, if you have petrol and a spark, it should run. If it runs fairly smoothly, assume the ignition (spark) is OK, and the problem lies in the carburettor. You will have to remove and strip the carb, and check for blocked jets. There is probably a very fine "idle jet" that is blocked - usually they look like little brass things with holes in the middle. Clean by blowing out and washing in petrol. (You can also buy carb repair kits which include all jets, seals, etc) To prevent recurrence, fit a filter in the fuel pipe to the carb - these cost about a quid at acessory shops, and should be replaced when you service the car.
If it runs rough, the problem is probably in the ignition. For what it costs (and if you haven't changed them recently), I would fit a new distributor cap and rotor arm, distributor leads, spark plugs and (if it isn't electronic ignition) contact breaker and condensor. Another option is to have somebody run the engine fast enough so as not to stall, then remove one plug lead at a time, careful not to get a shock! If a plug or lead is dodgy, you won't notice the difference; if the engine runs rougher, that plug is sparking OK!
(Electronic ignition is very powerful - the electricity jumps (sparks) across any gaps in the conductors in the leads, so you don't notice a problem. However, the sparking erodes the conductors further, increasing the gap, till suddenly the gap is too big to be jumped and the lead stops working. If the fault is on the distributor to coil lead, the car sudenly packs up altogether; if it is on a plug lead, you just lose one cylinder and it runs rough. I always used to carry a spare coil lead when I ran petrol cars, got me out of trouble twice!)
Keith, October 2004
