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Latest News Failing Secondary Ignition What a Technician needs to know when recognising symptoms that may be related to failing primary and secondary ignition components on earlier points type ignition systems.
Vehicle will start during cranking but stall when the key is moved to the “run or key on” position. During the engine cranking process, the power supply will by-pass the ignition ballast resistor (Ignition resistance) and supply the remaining primary circuit (low voltage components of the circuit) with cranking battery voltage. If the vehicle starts during the cranking process, it generally indicates that the cranking circuit is functioning. Releasing the ignition key to the “run or key on “position, will transfer the power supply from the crank circuit to the ignition resistance circuit to reduce the voltage supply to the ignition coil and remaining circuit components. A failed (open circuit) ballast resistor or failed ignition switch “on” circuit will now interrupt the power supply to the primary circuit and cause instant engine stall. A multimeter can quickly be used to check the voltage supply to the ballast resistor and ignition coil to determine if any open circuit conditions exist. Note: there have been conditions where the engine will not start during cranking but will sometimes start as the key is released from the “crank position” to the engine run position. A failed crank contact on the ignition switch or open circuit in the “crank bypass circuit” will generally cause this condition. Vehicle is hard to start during hot or cold cranking. There are of course many factors that can affect this condition. As mentioned in our previous Ignition – Condensers, Contact Sets, Distributor Caps and Rotors article, it is important that the ignition coil is the correct type for this system. That is: a 12V ignition coil is not generally fitted to a points system that utilises a ballast resistor. A reduced voltage supply through the ballast resistor to an incorrectly fitted 12V ignition coil will result in hard starting during all cranking conditions due to a poor spark output. Incorrect contact point gaps (large and small) affects dwell and in turn system operation. It is of course important to investigate the condition of the contact points as well as the distributor shaft cams that physically open the contacts. Wear on the cams and pitting on the contact point surfaces must be rectified to ensure correct contact point operation. Note: any major pitting on the contact points surface may be due to a failing condenser. Renewing the condenser with the correct part number or microfarad rating ensures long contact point expected life. Fitting an incorrect condenser generally results in a no start condition or premature contact point failure. Constant no start condition caused by no ignition spark at the spark plug HT leads. Prior to renewing any ignition components, there are some elementary simple checks to be carried out.
Spark at ignition coil output but not at spark plug HT leads. If a good spark is evident from the ignition coil to the distributor cap but not evident to the spark plug HT leads, the technician needs to investigate the secondary HT circuit to determine where the HT spark is tracking. Generally, the rotor button may deteriorate and cause a tracking of the HT spark to ground through the distributor shaft.
Note: A faulty distributor cap can also track the HT spark away from the designated cylinder position. Replacing with correct quality components will ensure that the individual components do not prematurely deteriorate and will allow the older much-loved vehicles fitted with this system to run smoother and maintain the engine performance expected with the emission levels maintained as low as possible. The Premier Auto Trade Ignition range includes hundreds of secondary ignition products from the world’s leading manufacturers, covering millions of vehicle applications in Australia and NZ. When you supply and fit products from Premier Auto Trade you can expect a product designed and tested to the vehicle manufacturer’s specifications offering OE form, fit and function. Premier Auto Trade distributes products throughout Australia via a network of specialised resellers and leading automotive groups. |
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