Bosch distributors are found on many different cars and are generally very
reliable. But after a high mileage you may find that the engine isn't running
quite as it should. If the rest of the fuel and ignition system is well tuned
but the car doesn't accelerate cleanly, the problem may lie in the distributor
Checking and freeing the mechanism is the only work you can do on the Bosch
distributor as spare parts are not available. If there is wear in the
distributor shaft bearings, a new unit is the only solution.
The design is conventional with the contact breaker points mounted on a
movable plate, which in turn sits on a fixed baseplate.
The vacuum advance unit is attached by screws to the side of the distributor
and connects to a small post on the upper movable plate by a link rod and
While it is possible to dismantle the Bosch unit for inspection, many
parts, such as the mechanical advance weight mechanism (also called the bob
weights) and the baseplates, cannot be bought as individual
To save buying a new or exchange unit, it is worth trying to get a
second-hand one from a scrapyard and either using the parts you need from
this or fitting the unit as a complete replacement.
You can, however, renew the points, condenser, drive gear and vacuum
You should first disconnect the battery by removing one of the leads to
avoid any possibility of a short circuit. Then remove the distributor from the
engine. Remove the points and condenser. Now you are ready to strip down the
Dismantling a Bosch distributor
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