Starting Problem

[JohnC]

My 924 Lux normally starts without problem after 2 or 3 turns of the engine. Howerver ocasionally (about 1 time in 20) it simply refuses to fire. When this happens, if jump leads are connected it starts immediately.

The problems occurs even after the car has had a good long run then then stood for most of the day - so it doesn't seem to be a low battery and definately not a 'hot start' problem. I have replaced the battery just in case.

As the problem is very intermittent it's hard to track down - any helpful suggestions welcome !

Someone suggested I replace the "ballast resistor" - can anyone explain the function of the ballast resisitor and if it's likely to be the casue of the problem ?

Thanks

Jhn Cooper

 

[924nutter]

Like you didn't expect me to. You don't mention the year of your vehicle, so here goes. It is recognised that due to the starter drawing some 200 amps, because of the need to turn over more modern, higher compression engines, the voltage available to supply the low tension widings in the coil can be a low as 9v, resulting in a feeble spark. What the manufacturers did to overcome this was to fit a coil whose optimum working voltage was 9v, but they were then faced with the problem of preventing coil burn out once the engine was running and the alternator was kicking out 14v. Enter the ballast resistor, which is placed in series with the coil during normal running. The coil is fed directly from an auxilliary contact on the sloenoid during the starting phase, effectively bypassing the ballast resistor. As far as I am aware vehicles fitted with the Bosch ignition module do not have an external ballast resistor, so if you have contactless ignition, and the module, I personally don't think that will be your problem. The trouble is, it could be many other things. The module, when it starts to fail can be a real pain to pick up, because before it packs up completely you can still get a nice fat spark, but it occurs at the wrong time. I speak from experience. It could also be the warm up regulator, a siezing fuel pump, all sorts of things. I'm sorry to say that this is suck it and see fault. Change one thing at a time, then you'll know what fixed it.