The high-tension (HT) or
carries high-voltage electricity. It runs from the
to the plugs. Any of these can break down and cause
Do not touch any part of the HT
with bare hands when the ignition is switched on. Work with pliers and screwdrivers that have thickly insulated plastic handles. Take care not to touch any metal parts of the tools.
Since HT-circuit checks involve using the car's own HT leads, begin by testing the leads to make sure that they are sound.
Remove or push back the cap from the end of the HT lead to expose the core connection.
Remove a lead from one of the sparkplugs, then
on the ignition.
Grip the detached central HT lead with insulated pliers, and hold its exposed end against the plug
. Flick open the contact-breaker points with a small insulated screwdriver.
between the end of the HT lead and the plug terminal shows that both the coil and
are in order.
An alternative test can be made by taking off all the plug leads to prevent the
from starting (number the leads to avoid later confusion).
Remove one of the plugs and reconnect it to a lead. Touch it against the
and watch for a strong spark when a helper turns the
If either test produces only a weak spark, and the HT leads are sound, suspect a faulty condenser. Check by fitting another condenser which you know to be serviceable (See
Fitting a condenser
Check the condenser connections. If the spark is no better, or if the first test gave no spark, the coil is faulty (See
Inspecting the ignition system
). Replace it if necessary.
It is possible for the rotor arm to
to the top of the contact-breaker cam. Detach the central HT lead from the distributor cap and hold it with insulated pliers. Switch on the ignition. Hold the exposed metal end of the lead about in. (3mm) from the rotor-arm tip.
Flick the points open. There should be no spark, or a feeble spark from static
. A strong spark means a short circuit.
Clean the cam and rotor arm of dirt and grease. If the trouble persists, examine the rotor arm for cracks and replace it if necessary.
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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