Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Ignition System
1991 Cadillac Seville STSSECTION Ignition System
- Disconnect tachometer wire from IDI module (if equipped). A shorted tachometer or tachometer circuit will not allow vehicle to start. Temporarily remove IDI assembly and install spark plug Jumper Wires (J-36012). Check for adequate spark with Spark Tester (ST-125). Check for spark on 2 adjacent plug wires (1-2 or 3-4, not 2-3). Leave matching plug wire connected while checking for spark. If spark jumps tester on both plug wires, check fuel system. If spark did not jump tester on either plug wire, go to step 4).
- If spark jumped tester on only one plug wire, disconnect plug jumper wires and remove coil housing. Disconnect coil harness connector at module. Install test light between module terminal "A" and control terminal for coil which did not spark. See Fig 1-Fig 3 .
RENDER: 1.0x
NO RELATED
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.