Ignition

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The 8-digit part numbers in parentheses are the corresponding Citroën part numbers. NA means models not fitted with any anti-pollution device. Years denote Model Years.

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You can always have an aftermarket tachometer sold in many car parts stores. However, these are additional units you have to place somewhere on the dashboard; not a nice thing to do if you want to keep the looks of your car as original as you can. But if you replace your instrument panel unit with one having a tachometer, you can have the same layout BXs with higher trim levels originally had. With a little work you can change the tachometer only but it would be even wiser to look for a complete GTi instrument panel and retrofit the coolant temperature gauge, too, which is also lacking from your dashboard. Study the description of this modification first.

Citroën originally fitted Champion spark plugs but specifies Eyquem and sometimes Bosch equivalents as well. The best choice would be the first one, however, there is a major problem: Champion and Bosch plugs are manufactured at many plants all around the world. Although the technology is supposed to be the same everywhere, there are significant differences between the quality of those plugs. Those manufactured in the Belgian and British factories of Champion and in German plants of Bosch are excellent but those from other countries are average or often quite bad. You can, unfortunately, find no indication on the package disclosing the actual production plant. So, unless you can be absolutely sure where your plugs come from, you should use Eyquem instead which is not worse than Champion by any means and is manufactured in a consistent quality.

Traditionally, stroboscopes were built with xenon flashlights such as those used in photographic flashguns. However, these flashlights require a 400-600 V voltage and even more for igniting them. Needless to say, electric shocks of such voltages are often lethal. Unless you have experience in building such high voltage circuits (including proper insulation) and also have measuring equipment to help with the process, you shouldn't even think of building one.

Fortunately, with the advances of contemporary semiconductor technology, there is no need for those flashlights. There are very high intensity LED diodes available which are perfectly suited for this task. These mostly AlInGaP (Aluminum-Indium-Gallium Phosphate) LEDs come with an intensity level in the range of 10,000 to 25,000 microcandelas, which is an awful lot compared to the 5-50 mcd value of common LEDs. If you even put it into a socket with a reflector and a focusing lens, its light will be so bright that—although it's not a laser diode—you should never look directly into the light rays. Such LEDs are about ten times more expensive than regular ones but in absolute figures that's not so terrible at all: around 3-5 EUR each. 

You should start the troubleshooting at the sensor in the engine. Use a voltmeter in AC measurement position and observe the voltage at the two terminals of the sensor as you rev the engine up (have either an assistant or a long meter probe). If you measure absolutely nothing, the sensor is suspect (although you can check it with an oscilloscope if you can find one somewhere). If you obtained some readout, repeat the check at the instrument panel, at the blue connector mentioned (one pin is ground, one is +12 V, but the remaining two should exhibit the same behavior as the terminals of the sensor). If the readout is identical, the tachometer is suspect. If you obtained no readout, trace the wiring back through the bulkhead to the engine compartment and repeat the measurement at every connector it passes. If you found +12 V in any of the sensor wires, you have a shortcut somewhere.