Start-Run Sequence LH 2.0/2.2 Version

1) During starter cranking, the distributor Hall sensor sends timing pulses to Ignition Control Unit (ICU)

2-a) The ICU uses these Hall Sensor pulses to trigger the Ignition Coil (– terminal) to initiate timed sparks from the coil.

2-b) At the same time, the ICU also propagates the pulses to the FI ECU, to allow FI operation (no ICU pulses means no Fuel pumping).

3-a) The Fuel Injection (System)* relay (previously energized at Key On) powers the AMM, IAC, ECU, Injectors, and Fuel (pump) relay coil + side.
* The System relay is adjacent to the Fuel relay (same relay type).

3-b) When ICU pulses are received by the FI ECU, it "energizes" the Fuel relay by grounding the relay coil (– side) to run the fuel pumps.

When all these things work, the engine runs until the Ignition is switched off, which in turn shuts down the FI system.

Known trouble spots on '84...

• 25 amp blade fuse, fuse holder, wiring to (and at) battery +
• Fuse 13 corrosion, poor contact (+12V to Fuel relay coil)
• 3-pin plug under glovebox (Y-R wire carries +12V from Fuel relay to pumps)
• No spark=no fuel (Hall sensor or wiring at distributor)


--
Bruce Young, '93 940-NA (current), 240s (one V8), 140s, 122s, since '63.