The pickup coil in your 1988 Chevy is located in the distributor. It provides an electronic signal to the ignition module that determines when the ignition coil is triggered and the spark plugs are fired. When the coil fails, the ignition system cannot be triggered to fire the plugs, and the engine will not start. Typically, the ignition module is replaced at the same time as the pickup coil due to the possibility of damage to the module when the coil fails.
Remove the distributor cap using a flat-blade screwdriver. Lay the cap and the plug wires attached to it aside. Turn the ignition key to the start position in short bursts until the rotor under the cap is pointing at the firewall. Turn the ignition key off and remove it from the ignition switch. Do not allow anyone else access to the keys until the procedure is complete. Mark the position of the rotor on the firewall and the position of the distributor housing on the engine block so that the distributor can be reinstalled in exactly the same position.
Unplug the electrical connector from the distributor. Remove the distributor hold-down bracket by unscrewing the 1/2-inch bolt using a distributor wrench. Lift the distributor out of the engine and place it on a work bench.
Push the roll pin out of the gear using a roll pin punch. The roll pin secures the distributor gear to the bottom of the distributor shaft. Slide the gear off the end of the shaft and slide the shaft our of the distributor housing. If the shaft seems to stick in the housing spray liberal amounts of spray parts cleaner on the shaft and work the shaft up and down until it slides from the distributor.
Remove the electrical connector attaching the pickup coil to the ignition module. Pop the small retainer clip that secures the pickup coil to the distributor housing using a pick to pry it up and off the housing. Lift the pickup coil off the housing.
Slip the new pickup coil onto the housing and secure it with the new retaining clip supplied with the new coil. Plug the electrical connector onto the ignition module. Install the distributor shaft and gear. Install the roll pin into the gear and tap it into the gear until it is flush with the surface of the gear.
Slip the distributor into the engine and align the rotor and housing with the marks on the engine and firewall. It may take several attempts to get it just right because the rotor will turn slightly as the distributor is lowered into place. Secure the distributor to the engine with the hold-down bracket and bolt.
Reinstall the distributor cap and start the engine. Set the ignition timing, using a timing light, according to the instructions in your service manual for the engine size of your 1988 GMC.
