Crank Triggers

A crankshaft trigger reduces the number of mechanical connections and areas of inconsistency that are found in a distributor pickup setup. The camshaft-to-distributor drive gear, distributor shaft, reluctor wheel, and pickup can all have clearances and tolerances that can cause timing variations, especially at higher rpms. A trigger wheel is directly connected to the crankshaft, minimizing any change in signal that is transferred to the pickup mounted nearby.

When converting to a distributorless ignition system, a crank trigger is needed to let the ignition box or ECU know where the crankshaft is in its rotation. This ignition input allows for a distributorless ignition system or a front- drive distributor to be installed depending on the needs for the application.

A crank trigger is an electrical component that provides an input signal to the ignition system based on the crankshaft position in its rotation, which will provide the most efficient timing of spark in the cylinders. It is primarily used in race applications as well as on engines that use ignition coil packs instead of a distributor.

A crank trigger ignition system works with simple operation. A trigger wheel bolted to the harmonic damper spins with either a sequence of teeth and gaps or magnets. A pickup is positioned close to the wheel and when the magnet or gap is sensed, it sends a signal to either a computer or aftermarket ignition box. This information is then used by the ignition ECU to determine when to tell the coil to send voltage to either the distributor or spark plug to fire at the correct time.

The crank trigger wheel is installed on the front of the harmonic balancer with the correct side facing outwards. If a crankshaft pulley is used, the thickness of the trigger wheel will need to be matched on the pulleys of any driven accessories such as the water pump, alternator, vacuum pump, or any other belt driven component with spacers (on average about 3/8"). This will allow belt alignment to remain correct to prevent slippage and throwing.

The first step in setting up a crank trigger is to install the trigger wheel on the harmonic damper balancer. Next, the pickup and mounting bracket are installed in line with the trigger wheel. The distributor rotor needs to be lined up with the #1 spark plug wire terminal under the distributor cap and the engine at top dead center (TDC) for the #1 cylinder. The pickup has two wires that will connect to an ignition box or computer as an input. In addition, the air gap between the pickup and the wheel needs to be close enough for a strong signal, but not too close that the trigger wheel makes contact. This is especially important under load and at higher rpms (typically between .025 to .050") where the distance can change to the pickup. Once all connections and hardware are confirmed in the correct position and tightened properly, the engine can be started. Timing can then be fine-tuned to meet your engine's needs.