Checking Firing Pulse At Ignition Coil
- Make an adapter to fit between ignition coil connector and test diode (999-5280
). Connect test diode. See Fig 1
.
Courtesy of VOLVO CARS OF NORTH AMERICA.
- Start engine. Diode should flash if signal is present. If signal is present, go to step 5). If no signal is present, connect voltmeter between ground and control unit terminals connected to each ignition coil.
- If voltage is about 3.5 volts, an open circuit is present between control unit and ignition coil. If voltmeter indicates 60-100 millivolts, connect diode tester with positive side connected to control unit terminal for cylinder to be checked and to terminal No. 1 on corresponding ignition coil connector. Check components with leads reversed.
- Connect diode tester with positive side connected to ground and to terminal No. 1 on ignition coil connector. Check components with leads reversed. If fault is present, check wiring.
- Remove coil and plug. Install another plug in cylinder. Install original plug in ignition coil. Start engine and check for spark. If no spark is present, check whether coil or plug is faulty. Install plug in another coil. If spark is present, replace original coil. If no spark is present, replace spark plug.