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"Can someone tell me, if there is no pulse from the RPM sensor, do we have a no spark condition or no fuel condition, or both?"
• Both. Because it's the CPS pulses that trigger/time the ignition, and it's the Ignition CU's pulses that "allow" Fuel pumping.
[See sequence list below]
"Same question for radio suppression relay"."
• RSR allows +12V to injectors on turbo and NA. Also +12V to Coil 15 on turbos.
Start-Run Sequence LH2.4 or REX-Regina
1) During starter cranking, the Crank Position Sensor sends timing pulses to Ignition Control Unit (ICU = EZK or REX)
2-a) The ICU uses these CPS pulses to trigger the Power Stage (aka Ignition Amplifier), which initiates spark 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 FI operation).
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 in the white case with the Fuel relay.
* NOTE that on 700/900 cars with the square pump relay, the RSRelay becomes the "System" relay, as described above.
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.
--
Bruce Young, '93 940-NA (current), 240s (one V8), 140s, 122s, since '63.
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