Lucas AB17 ECU Ignition
Car Won't Start - No Spark at Plugs?

  1. If you have established there is no spark at the plugs before doing anything else check the cam belt isn't broken -- if the belt is broken rotor arm won't be turned by the camshaft :-(
  2. Carefully examine the coil, distributer cap and leads for cracks or signs of damage.
  3. The distributer cap and rotor arm on OHC Rover engines tend to suffer from neglect as the cap is difficult to remove for cleaning, the rotor arm on early models also tends to crack particularly if it is the type with a metal insert, later type  OEM rotor arms are often  marked with a dab of red paint.
  4. Due to its location often on high mileage Rovers the inside of distributer cap may be contaninated with of oily residue. If this is the case the cap may be carbonised and need replaced. I always buy OEM rotor arms but I prefer non Rover/Lucas distributer caps as the aftermarket types are retained by more convenient slot headed screws, The oil seal inside the distributer is very easy to renew and this should be done at the earliest opportunity and the crankcase breather cleaned at the same time.
  5. After looking for any obvious broken connections or dampness , turn the engine over on the starter; the tachometer needle should give a slight kick as the engine is turned over. If it doesn't this points towards a low tension fault. If the needle is kicking this would tend towards eliminating  the ECU and crankshaft angle sensor as a possible cause ;-)
  6. One possible low tension fault is a blown fuse, unlike cars built in earlier eras modern  Rover & Austin-Rover Group cars have the ignition fed through a fuse; on any 80s and 90s Rovers I have worked this fuse is located in the internal fuse box below the dash and is usually one of the fuses near the top right of the fuse box.
  7. Even if the needle kicks check 12 volts  is getting to the coil via the green wire.
  8. Put a multi meter set to the 20 volts dc scale  between the terminal connected to white/black wires on coil and earth  when the car is turned over on the starter you should see voltage rising and falling as the ECU pulses the coil to ground. A failure on this test points towards connection or ECU problems.
  9. Check that the 12 volt power via the green wire to pin 9 of the ignition ECU is getting battery while engine is being cranked.
  10. Check the crank shaft angle sensor (CAS) voltage output at cranking speed, also check the resistance and examine the cable and plug for damage, see page on CAS for full details.
  11. If CAS output looks OK check very carefully all the connections to the ECU, particularly the earth grounding through the black wire to pin 12. If this should show a voltage of more than 0.2 volts when cranking use a "Scotchlok" connector to tap into the wire and run an earth straight to the battery -Ve terminal.

If  after working through this check list there is still no spark at the plugs the evidence would tend to point to either an Ignition ECU or Ignition Coil fault, this will soon be covered in detail in another section.

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