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LUCID's Start Run Sequence one question 200 1989

posted by  TONY H on  Mon Jul 19 02:33 CST 2010
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last visit: Fri Oct 17 16:39 CST 2014
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Bruce did a great job listing this ( Below) That's why I keep it inm my Favorites. One question though.
I can understand the ICU seeing the Cranking and sending Voltage to the Coil. I still do not understand the Amplifiers job. Does it interpret a Signal from the ICU and then release 12V to the Coil?
Which one of these starting sequences can Crap out and NOT leave a Code?


http://www.brickboard.com/RWD/volvo/1417685/740/760/780/required_startrun_sequence.html


This is what has to happen after the short pump cycle at Key On:
[You have REX ignition with Regina FI system]

Start-Run Sequence

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 Fuel operation (no ICU pulses means no Fuel 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 same white case as the Fuel relay.

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.

Determining whether or not there is spark at the plugs (2a) — and whether or not the plugs are getting gas (3b) — makes a good no-start "starting" point.

For example, if 2a fails due to a bad Power Stage/Amplifier, there will be a no-start with gas-wet plugs. If 2b fails (practically never) symptoms will be Fuel-related: a no-start with spark at the plugs, but plugs remain dry.

--
'75 Jeep CJ5 345Hp ChevyPwrd, two motorcycles, '85 Pickup: The '89 Volvo is the newest vehicle I own. it wasn't Volvos safety , it was Longevity that sold me http://home.lyse.net/brox/TonyPage4.html








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    LUCID's Start Run Sequence one question 200 1989

    uid 18083's pic
    posted by  lucid on  Mon Jul 19 07:47 CST 2010
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    last visit: Fri Oct 24 12:31 CST 2014
    [RELATED]

    Hi Tony,

    "One question though.
    I can understand the ICU seeing the Cranking and sending Voltage to the Coil. I still do not understand the Amplifiers job."
    • Answer: The ICU doesn't send any voltage to the coil. See step 2-a below, where I used the word "trigger" as short-hand for: "causes the Power Stage/Amplifier to make and break the ground side of the coil primary winding" (12V is always on the + side). That's what "initiates" spark from the coil. (wish I hadn't said "spark" from the coil though. Hi voltage is better.)
    [Think back to the old days of ignition points -- same thing.]

    Question two of one;-)
    "Which one of these starting sequences can Crap out and NOT leave a Code?"
    • Answer: Good old 2-a)
    The ICU uses these CPS pulses to trigger the Power Stage (aka Ignition Amplifier), which initiates spark from the coil.
    • There is no test to see if the CPS/ICU pulses ever get to the Power Stage, or if they do, that the Power Stage does its thing. So if we get 2-b without 2-a, we have fuel pumping and injectors squirting, but no spark at the plugs, like I explain at the bottom of the canned sequence.

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








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      LUCID's Start Run Sequence one question 200 1989

      posted by  TONY H on  Mon Jul 19 08:15 CST 2010
      Author: [PROFILE] [EVERY POST] [THREADS] [BEST POSTS] RSS Feed     [IGNORE ALL POSTS]
      last visit: Fri Oct 17 16:39 CST 2014
      [RELATED]

      Ahhh, The Amplifier acts as an old school Condensor (Capacitor).

      "Question 2 of 1".. alright... you got me.

      Ok so If the ICU is bad.. That is about the only scenario that I would not see a code...
      I'm sure my Brothers BMW is the same but different. just trying to understand a typical Fuel injected startup.
      Trying to help trouble shoot from 2000 miles away.
      Last report.. He has Spark and no fuel. and no codes It ran great on day, Crank but no start the next day. He says he is getting triggering at his Crank sensor and Cam sensor.

      Thaks for the Lesson

      --
      '75 Jeep CJ5 345Hp ChevyPwrd, two motorcycles, '85 Pickup: The '89 Volvo is the newest vehicle I own. it wasn't Volvos safety , it was Longevity that sold me http://home.lyse.net/brox/TonyPage4.html







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