Ignition coil primary voltage tests Perfectly good ignition coils, plugs and wires are often replaced because the technician observed poor secondary spark. However, low primary voltage might be the real culprit! Be sure to do a primary voltage drop test before condemning the coil! 1. Connect a meter between the battery positive post and the coil primary positive terminal. 2. Test KOEO and KOER. (If a no start, check engine cranking.) 3. Only 0.2 V is acceptable. If the test results fail, you need to isolate where the voltage drop is, starting between the batter post and cable end, then working your way up. Don’t try this with a test light, because it won’t tell you anything useful. You need to find out if there is significant electrical resistance, not whether there is any power there whatsoever. Using the low amp probe on DIS Not sure where to clamp on with your low amp probe to measure coil current in DIS? Most DIS coil pack electrical connectors have a single power feed, regardless of the number of coils in the pack. Connect here to get a good overall look of ignition coil amperage. To get a look at the spark plug pair, connect to the one coil primary control wire leaving the coil pack.
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