Pick-Up Coil Short & Resistance Checks
- Disconnect pick-up coil leads from HEI/EST module terminals "N" and "P". Set ohmmeter to middle scale and connect one lead to either pick-up coil lead and the other lead to distributor housing. See Fig 1. Flex pick-up coil leads by hand to check for intermittent shorts to ground. Reading should be infinity at all times. If not, replace pick-up coil.
- Connect ohmmeter between both pick-up coil leads. Check for intermittent opens by flexing wires and connectors. Resistance should be 500-1500 ohms. If not, replace pick-up coil.
Fig 1: Checking Distributor Pick-Up Coil Integral coil system shown. External coil testing is similar. Courtesy of General Motors Corp.
NOTE:
Diagnosis of HEI systems with EST and EST/ESC require thorough understanding of Computer Command Control (CCC) system. For testing, refer to the IGNITION SYSTEM CHECK flow chart in the CCC TBI TESTS W/ CODES
article in the ENGINE PERFORMANCE section. For diagnosis of HEI system, refer to following diagnostic chart. See Fig 3. Testing applies to HEI systems with mechanical weights and vacuum advance.