No current for the distributing cap for the ignition to start the engine
When you say 'No Current' do you mean no electrical supply. In fact there is vary little current delivered to the central lead of the distributor. The working principle:
Low voltage (12 volts) is supplied to the 'coil'. The coil behaves like a transformer in reverse, instead of stepping the voltage down it steps the voltage up. Inside the coil is, as the name suggests, a coil. The primary coil is the low voltage (12v) supplied and consists of just a few windings. The secondary coil consists of very many windings. The ratio of the low number of windings of the primary coil to the large number of windings of the secondary coil is the factor by which the 12 volt supply is stepped up. The coil output consists of very high voltage charge (tens of thousands of volts). This high charge is delivered with negligible current (hence my earlier query). The charge is conveyed by high tension lead to the centre of the distributor. The distributor arm 'distributes' the charge to each cylinder in turn. The charge is so great that it jumps the spark plug gap creating a spark and hence ignites the compressed fuel/air mix.
That's the boring bit, to effect a remedy check the low voltage leads to the coil and check that 12volts can be measured on a meter. A bit crude this, but ease the insulation cap back on the central distributor terminal put your finger on it and have someone turn the engine over. A hell of kick up the arm tells you that the high tension side of the coil is working :-). The voltage is so high that it most likely beyond the ability to be measured using a standard volt meter. If not there is 1) a possible short or break in the high tension cable between the coil and distributor or 2) the coil is fried. Either way it is not too expensive to change these. Also check the contact breaker points within the distributor are clean and are of the correct gap setting. An emery board/nail file I find is a convenient and quick way to polish the opposing contact points.
Apr 18, 2010 |
2004 Jeep Grand Cherokee