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The CPS is a sensor that generats a timing pulse once per revolution. It's pulse goes to the ignition CU, no where else.
Start Sequence
1) During starter cranking, the Crank Position Sensor sends timing pulses to Ignition Control Unit (ICU)
2-a) The ICU propagates these timing pulses to the Power Stage (aka Ignition Amplifier) to initiate spark at the coil.
2-b) The ICU also propagates these pulses to the FI ECU, to allow FI operation
(no ICU pulses means no FI operation).
3-a) The "System" relay (previously energized at Key On) powers the AMM, IAC, ECU, Injectors, and Fuel relay coil + side.
3-b) When ICU timing pulses are received, the FI ECU "energizes" the Fuel relay (completes the relay coil ground 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.
• Jumpering the LEFT side contacts of fuses 4 and 6 will bypass both the 25A blade fuse and the Fuel relay—and will power up both pumps immediately.
If you have both spark and fuel at the plugs, the only thing missing is compression. Large amounts of unburned gas can wash the cylinder walls clean of oil, preventing the piston rings from sealing (no compression). Or the timing belt may have jumped a few teeth, affecting compression.
Burnt fuse 6 is a mystery because it's not wired to anything on US cars till '91. The fuse cover label is wrong, for US market.
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Bruce Young, '93 940-NA (current), 240s (one V8), 140s, 122s, since '63.
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