Direct Ignition System (Dis): Notes

CAUTION: Avoid running engine if there is a possibility of the secondary circuit becoming open. Ignition power stages and/or the ignition coils could be damaged through excessive energy being reflected back into the primary circuit.

Ignition and spark distribution are controlled by DIS. On Discovery Series I, DIS uses 4 double-ended ignition coils located at the rear of the engine. On Discovery Series II and Range Rover, DIS uses 2 quad-ended ignition coils located at the rear of the engine. On all models, ECM provides internal switching of ground circuit for each coil, which operate on a waste spark principle. A spark is delivered simultaneously to 2 cylinders, one on its compression stroke and the other on its exhaust stroke. Coil No. 1 feeds cylinders No. 1 and 6. Coil No. 2 feeds cylinders No. 5 and 8. Coil No. 3 feeds cylinders No. 4 and 7. Coil No. 4 feeds cylinders No. 2 and 3. Failure of any coil will cause a misfire in 2 cylinders.

Ignition timing is controlled primarily as a function of engine speed, temperature, load, knock and idle speed controls, and A/T shift control. Engine load is sensed by Mass Airflow (MAF) sensor. Engine speed is sensed by a Crankshaft Position (CKP) sensor. ECM determines correct firing sequence and timing of ignition coils from input provided by Camshaft Position (CMP) sensor. An ignition coil fault is indicated by illumination of the MIL.