Table of contents: The engine turns over but does not…🠇 The engine is misfiring 🠇
1. Most engine performance problems are usually caused by a faulty ignition system in one of the circuits: low or high voltage. There are two main signs that indicate a faulty ignition system: either the engine does not start and "fires", or it starts poorly and misses a spark. If the misfire becomes regular, i.e. the engine only runs on two or three cylinders, the problem most likely lies in the secondary circuit (high voltage circuit). If the flash misfire appears and then disappears, either of the two circuits may be faulty. If the engine suddenly stalls or does not start at all, the primary circuit is most likely faulty (low voltage). Loss of power and engine overheating can be caused not only by a poorly adjusted carburetor, but also by a faulty distributor or poorly adjusted ignition.
The engine turns over but does not start
2. If the engine does not start and everything was fine the last time you used the car, you should first check if there is fuel in the tank. If the engine turns over normally with the starter and the battery is well charged, then the problem most likely lies in the high or low voltage circuit. Check the high voltage circuit first.
3. One of the common causes of problems with starting the engine is damp spark plug wires and distributor cap. Remove the distributor cap. If there are traces of moisture inside, wipe the cover and wires dry. For a one-time solution, you can spray a small amount of Holts Wet Start on the wires and the inside of the distributor cap. As a preventative measure, you can periodically use Holts Damp Start, which forms a protective coating that prevents moisture from accumulating in the ignition system. Holts Cold Start will help start the engine even with a very poor spark. When finished, put the distributor cap back in place.
4. If the engine still does not start, check whether current is reaching the spark plugs. To do this, disconnect the wire from each spark plug in turn and, holding it (with a hand in a rubber glove or a tool with insulated handles) at a distance of 5 mm from the cylinder block, turn the engine with the starter.
5. There should be strong sparking with a regular blue spark between the end of the wire and the block. Once you are sure that current is reaching all the spark plugs, you should remove them, clean them and adjust the gaps. After this, the engine should start.
6. If the current does not reach the spark plugs, disconnect the high-voltage wire from the central terminal on the distributor cap and bring it to the cylinder block, as before. Turn the engine over with the starter. A quick succession of blue sparks between the end of the wire and the block indicates that the ignition coil is OK and the problem lies with a cracked distributor cap, a faulty rotor, or a lack of good contact between the carbon on the distributor cap and the spring on the rotor.
7. If there is no sparking between the end of the wire and the block, check its connection to the coil. If it is ok, proceed to checking the low voltage circuit. It is possible that the breaker contacts are in poor condition. Clean the contacts and adjust the gap between them as described in section 2. If sparking still does not appear, proceed to the next checks.
8. Use a 12V voltmeter or tester lamp. With the ignition on and the contacts open, check the voltage between the low-voltage wire going to the coil (marked "+") and ground. A lack of voltage indicates a break in the supply wire coming from the ignition switch. Inspect the contacts on the switch to ensure that none of the wires have come loose. Reconnect the wires and the engine should start. If the voltmeter or lamp shows voltage, the coil or capacitor is faulty, or there is a break in the wire between the coil and the distributor.
9. Disconnect the capacitor wire from the breaker contacts and, with the contacts open, check the voltage between the moving contact and ground. If voltage is present, the fault lies in the capacitor. Replace the capacitor and the car should start.
10. If there is no voltage between the moving contact and the ground, measure the voltage between the ground and the (-) terminal on the coil. If voltage is present, there is a break in the wiring between the coil and the distributor. The absence of voltage confirms that the coil is faulty and should be replaced, after which the engine should start. Don't forget to put the capacitor wire back in place. When testing, it is enough to insert a piece of paper between the contacts to keep them open.
The engine is misfiring
11. If the ignition is misfiring regularly, start the engine at fast idle speed. Remove the spark plug caps one by one, listening to the engine noise. (The cap should be held with a rubber-gloved hand or through a dry cloth to avoid electric shock).
12. When removing the cap from a non-working spark plug, the engine noise will not change, but in other cases the misfire will increase.
13. Disconnect the wire from the non-working spark plug and, holding its end 5 mm from the cylinder block, start the engine again. If there is strong, regular sparking, the problem lies in the spark plug.
14. The spark plug may become weak, its insulator may be cracked, or the electrodes may be burned so that the gap between them becomes too large for a spark to jump. In the worst case, one of the electrodes may break off. Depending on the situation, replace the spark plug or clean it and adjust the spark gap. Repeat the check again.
15. If there is no sparking between the block and the end of the wire, or if there is poor, irregular sparking, check the ignition wire. If its insulation is cracked or worn, the wire should be replaced. Check the wire connection to the distributor cap.
16. If after this the spark still does not appear, inspect the distributor cap for tracking marks (very thin black lines running between the electrodes or between the electrodes and other parts of the cap). Along these lines, the current flows along the surface of the cap to ground. If traces of tracking are detected, the only solution is to replace the cover.
17. In addition to incorrect ignition timing, misfiring can be caused by other reasons:
- a. Coil malfunction (irregular flash skipping)
- b. Damaged wire or poor contact in the low voltage circuit
- c. Capacitor malfunction (capacitor is broken)
- g. Mechanical failure of the distributor (damaged roller or broken spring of the contact breaker)
18. If the ignition timing is too late, the engine will tend to overheat and its power will be noticeably reduced. If the engine overheats and does not operate at full power, and the ignition timing is set correctly, the condition and adjustment of the carburetor should be checked.