For 1990-2009 cars

# NO/HARD START POOR PERFORMANCE COIL/PICK-UP INFORMATION

#### MODELS AFFECTED: ALL MODELS -1976-1984 (EXCLUDING CIMARRON)

Hard starting or no starts can result from wrong ignition and pickup coils or ignition coil/pickup coil mismatch in HEI equipped vehicles. A car with a coil mismatch may start and run poorly with a scattered coil primary pattern and erratic secondary pattern when viewed on an ignition scope.

Ignition and pickup coils are wound to compensate for factors such as battery location and starter cable routing. The starter or starter solenoid inrush current causes a transient voltage to appear in the pickup coil. A positive transient will trigger the HEI module, causing the coil to energize. This will result in an attempted firing of a plug. The proper pickup coils are matched to the vehicle application and are wound such that the transient voltage is a negative voltage spike which the module will ignore.

Two combinations of ignition/pickup coils have been used in Cadillac V- 8 and V-6 cars since 1979; a "yellow dot" and a "white dot" (see Figure 1).

The white and yellow dot igniting coils and pick-up coils can be identified by wiring color and configuration as shown in Figure 1. A distributor built with a yellow or white dot coil combination can sometimes be identified by a white dot or yellow dot on top of the distributor, on the coil cover.

Only two ignition coil part numbers are used to service Cadillac integral coil distributors from 1976 to present. The part numbers are listed on the following page with applications. (NOTE: The September, 1983 edition of "1983 C-D-E-K-Z 1984 D-E-K-Z Parts and Illustrations Catalog" lists incorrect service part numbers for both types of coils. The part number listed is a production part number. If ordered, the part numbers below will be provided.)

Several pick-up coils have been used from 1976 to present. They are electrically the same with different connectors for four, five and seven terminal HEI modules. The green and white wires are reversed in the connector for yellow dot and white dot coils as shown in Figure 1. Consult the GM Parts Book for part numbers for specific applications.

Pick-Up/Ignition coil applications are as follows:

YELLOW DOT WHITE DOT (Ign. Coil P/N 1985473) (Ign. Coil P/N 1985474) ----------------------- ----------------------- 76-77 C, D, E, Z 76-77 K 78-79 425CID 78-80 350 CID (EFI) 80-84 368 CID 80-82 4.1L V-6 82-84 HT4100 FWD (E/K) 82-84 HT4100 RWD (RWD-C & DW)

Most pickup/ignition coil mismatch problems are created by replacing either an ignition coil or a pickup coil with a wrong part number. Other cases have occurred when "E/K" (front wheel drive) distributors are swapped with "C", "D", "Z" distributors (rear wheel drive) or vice versa. For an HT4100, the distributors are identical except for the ignition coil/pickup coil combina- tion and part number.

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.