The ignition module on a 1990 Chevrolet Silverado V8 is inside the high energy ignition (HEI) distributor cap. HEI ignition provides hotter spark, which means that the fuel in the cylinders ignites faster, making starting easier and producing more horsepower. An HEI ignition with a good module can produce up to 40,000 volts as opposed to under 20,000 volts for the old point-style ignition.
Mark the plug wire on the distributor cap that is in the No. 1 position with shoe polish or liquid eraser. The No. 1 wire runs from the distributor to the first cylinder closest to the front of the engine on the driver's side. Push down on the distributor retaining springs with a screwdriver. Turn the springs 1/2 turn. Lift the distributor cap off the distributor.
Place a dot on the side of the rotor with the liquid eraser or shoe polish. Make another mark on the base of the distributor. When you replace the rotor, you will use these marks to line the rotor up, so make sure the dots are where you can easily see them and are in direct line with each other. Lift the rotor off the distributor shaft.
Remove the two screws holding the module onto the distributor housing. Lift the module out of the distributor housing.
Coat the mating surface of the new module with the silicone lubricant that comes with the module. Set the new module on the housing, then replace the two screws and tighten them so they are just snug.
Slide the rotor onto the distributor shaft, making sure you line up the dots you made in Step 2. Set the cap onto the distributor, making sure the wire in the No. 1 position is pointing to the No. 1 cylinder. Press the retaining springs down and rotate them 1/2 turn with the screwdriver until they hook under the distributor base.
