Many earlier cars still use a points-type ignition. While this has been replaced by transistorized ignition, there are good reasons to keep it original. If you are doing a full restoration, of if you just trust your breaker-points car that will survive a nuclear explosion, this technote is all about points!
This technote is still in it’s beta version. More will be added very soon!!
Breaker points control the ignition coil – they break the ground signal to the coil to tell it when to fire. The way it works is a cam on the distributor shaft forces the points to make contact. This signal goes through the condenser, which prevents the coil from discharging back through the points after firing. This charges and fires the igniton coil, which in turn fires the charge down the coil wire, and into the top of the distributor where the rotor spins it to the correct spark plug. At left is a diagram of an exploded distributor.
A VW distributor has both centrifugal advance and vacuum advance.
Breaker points need to be checked every 6000 miles. Points can actually be cleaned up a bit, but it is generally recomended to replace them. Replace the condenser at the same time, it is usually the cause of badly burned and pitted breaker points.
The proper spec for adjustment of the points with a feeler gauge is 0.4mm (0.016 inch). Turn the engine until the cam is at it’s farthest point, pushing the moving point against the fixed point. Now, loosen the holding screw, and make a gap to insert the feeler gauge. Adjust it so that the points just grip the gauge. Tighten the holding screw.
The proper Dwell angle for setting is 44° to 50°. The wear limits are 42° to 58°. Check the dwell at 1000rpm. compare this reading to a reading at 2000rpm. If the readings differ by more than 1°, that means you have bad distributor bearings. This will cause strange running problems in the ignition system. Replace the bearings, or replace the distributor.
The recomended spark plug gaping is 0.7mm (0.028 inch) Do not use platinum spark plugs. These engines were designed for, and run best with Bosch Super or Bosch Super + copper spark plugs.
Here’s a few disadvantages, or things to watch out for with points
- Breaker points wear out, and need to be replaced
- Wet breaker points screw the igniton up, use WD-40 to dry them (WD stands for water dissipator, you know!)
- Distributor bearings need to be perfect
- Don’t leave the ignition on while the car is not running for long periods, it can ruin the points
A later style ignition system can make for a more reliable igniton system. This adds a hall sender in the distributor that never needs to be replaced, and a transistor unit that fires the coil. Unfortunately, problems with the transistorized system are harder to diagnose.