|
"I checked the ECU impulses at the PowerStage and got a steady 1.0 volt - no oscillation - in KPIII.
So one or all of the following is bad:
1- Crank Position Sensor, resistance tested 167.5 ohms (range = 170-400) Certainly suspect (numerically) but I don't know if that reading means it's NFG
2- wiring between PS and ECU
3- ECU
The term "ECU" is generally used here to mean the Fuel Injection Control Unit. As such, the ECU has no part in pulsing the Power Stage. Although the CPS is a good suspect, all the followup chatter about the various ECU options is irrelevant, if a spark failure is suspected. That's the job of the Ignition CU (ICU), which hardly ever fails (see step 2-a in the sequence below):
Start-Run Sequence
1) During starter cranking, the Crank Position Sensor/CPS 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) At the same time, the ICU also propagates these timing pulses to the FI ECU, to allow FI operation
(no ICU pulses means no FI operation).
3-a) The FI System) relay (previously energized at Key On) powers the AMM, IAC, ECU, RS relay/Injectors, and Fuel (pump) relay coil + side.
3-b) When ICU pulses (2b) are received by the FI ECU, it "energizes" the Fuel relay (completes the relay coil ground side) to run the fuel pumps.
When this sequence is successful, the motor starts and 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.
|
