Function of the distributor finger in the ignition system
The distributor finger (also known as the distributor rotor) sits on the distributor shaft in the ignition distributor and distributes the high voltage from the ignition coil cyclically to the individual spark plug terminals. It rotates synchronously with the camshaft and ensures that the ignition voltage is passed on to the corresponding spark plug at the right time.
A perfectly functioning distributor unit with the correct distributor finger is essential for
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even ignition pulses
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stable combustion
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smooth engine running
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optimum performance
Structure & position in the ignition distributor
A distributor finger typically consists of:
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insulating plastic or thermoset material - low intrinsic conductivity
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contact-safe metal cap/conductive contact - as contact surface to the ignition cable cap
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rotating bearing contact - for ignition coil connection
The distributor finger internally connects the high-voltage output cap of the ignition coil to the individual spark plug terminals via the ignition cables.
Selection by reference number & engine type
The right distributor finger should be selected using the reference number, as engine variants differ in terms of distributor geometry, contact shapes and shaft mounting.
Recommended selection steps:
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Check the reference number of the old part
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Determine engine type & year of manufacture
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Select suitable distributor finger
A structured OEM comparison reduces incorrect orders and installation problems.
Installation & maintenance instructions
The following applies when replacing:
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Switch off the ignition beforehand
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Remove distributor cap and check bearing contact
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Remove the old distributor finger
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Position the new distributor finger correctly (latching nose/position)
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Replace distributor cap and check fit
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Test engine running
Ensure that the contacts are clean and firmly seated to prevent spark losses or interruptions in the ignition circuit.
Diagnosis & typical fault patterns
Signs of a worn or damaged distributor finger are
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Starting problems or misfiring
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Unsteady idling
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Jerking or loss of power
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Irregular spark distribution
Regular visual and functional checks as part of maintenance prevent ignition problems and ensure constant engine performance.
