Ignition systems have evolved from a distributor to a completely solid state electronic system with no moving parts.
No distributor means there is no distributor cap or rotor to replace. Also no troublesome vacuum or mechanical advance mechanisms to cause timing problems.
(DIS) Distributorless Ignition Systems are controlled by the on-board computer.
In place of the distributor, there are multiple coils for the new (DIS) Distributorless Ignition System.
The components of Distributorless Ignition Systems are:
- A – Ignition Coils
- B – Spark Plug
- C – Ignition Control Module (ICM) or Ignition Control Unit
- D – Ignition Switch
- E – Battery
- F – Crankshaft Triggering Device
- G – Camshaft Triggering Device
The evolution of ignition systems has provided a number of benefits.
Even so, that does not mean they are trouble-free.
Failures can and do occur for a variety of reasons.
So knowing how to identify and diagnose common (DIS) Distributorless Ignition System problems can save you a lot of guesswork. This will help the next time your engine cranks but refuses to start, or one that runs but is missing.
If an engine cranks but will not start, is it fuel, ignition or compression? Ignition is usually the easiest of the three to check because on most engines, all you have to do is pull off a plug wire and check for spark when the engine is cranked. On coil-over-plug (DIS) Distributorless Ignition Systems, there are no plug wires so you have to remove a coil and use a plug wire or adapter to check for a spark.
Testing The (DIS) Distributorless Ignition System
If there is no spark in one cylinder, try another. No spark in any cylinder would most likely indicate a failed DIS module or crankshaft position (CKP) sensor. Many engines with electronic fuel injection also use the crankshaft position sensor signal to trigger the injectors. So, if there is no spark and no injector activity, the problem is likely in the crank position sensor. No spark in one or two cylinders that share a coil would tell you a coil has probably failed.
The coils in (DIS) Distributorless Ignition Systems function the same as those in ordinary ignition systems, so testing is essentially the same. But the driveability symptoms caused by a weak coil or dead coil will be limited to one or two cylinders rather than all the cylinders.
Low MAP sensor output voltage or a coolant sensor that always reads cold will allow more spark advance than normal. This, in turn, may cause detonation (spark knock) problems when the engine is under load. So too can a faulty knock sensor or an EGR valve that is not working.
High MAP output voltage or a misadjusted throttle position sensor can have the opposite effect. This would cause the spark control system to retard timing more than normal. Retarded timing will reduce performance and fuel economy.
Do not forget, too, that ordinary secondary ignition problems can also cause misfires with (DIS) Distributorless Ignition System the same as a conventional ignition system. A bad spark plug wire or a fouled spark plug will act just like a weak or bad DIS coil.