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Fuel & Exhaust

Carburetor type

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Citroën used Weber and Solex carburetors...

EFI and EMS systems

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Citroën used various systems of several manufacturers... 

Exhaust system

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You can delay the corrosion if you use stainless steel exhaust components. For instance, Walker, a widely known aftermarket manufacturer of exhaust parts has a family named Aluminox. These parts are made of stainless steel and covered by a layer of aluminum alloy. The estimated life of these exhaust components exceeds five years under normal use while their price is only about 30% higher than that of the standard components. The last time I asked it was only available for the diesel models.

Fuel filter

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Citroën specifies the following filters:

Fuel injection basics

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Citroën used various systems of two manufacturers, Bosch and Magneti Marelli. All those systems operate on very similar principles so troubleshooting them involves more or less the same steps.

There are two basic categories: fuel injection (EFI) and engine management (EMS). EFI systems, as their name implies, are responsible for the injection of fuel only, the ignition sparks are created using traditional methods (a breakerless distributor). EMS systems, in contrast, govern both fuel injection and ignition themselves.

Injection parts on the CX

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

Injection system layouts

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The components of the various systems and their interoperation can be studied on the following diagrams...

Testing the EFI & EMS components

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There are basically two electrical measurements used in testing the various components. Voltage tests should be carried out with the ECU connector connected (unless otherwise stated in the test description). The cleanest method is to use a Break Out Box (or BOB), which is an extension connector placed between the ECU connector and its plug, making the various terminals accessible for measurements. If no BOB is available, use backprobing: peel back the insulating boot from the plug and attach the probe to the relevant pin.

Trouble with fuel level meter

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Although theoretically this might be a failure of either the meter or the level transmitter, the second one is much more likely and, first of all, much easier to check (to get at the meter you would need to remove and disassemble the instrument panel).

Unleaded fuel

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As a general rule, older engines (up to 1987 approximately) are not explicitly designed to run on unleaded fuel. Later engines are capable if the necessary adjustments are made. A few engine models are capable of running on both kinds of fuel without any adjustment. And finally, every car equipped with a catalytic converter, either in the factory or with an aftermarket product, must be run on unleaded fuel only. Lead is poison to the catalytic converter and the oxygen sensor, meaning that even one tankful of leaded fuel can cause serious damage to these delicate and painfully expensive parts.