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2G No fuel in #3 or #4

Posted by Jacob_Barnes520GST, Nov 3, 2018

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  1. Jacob_Barnes520GST

    Jacob_Barnes520GST Proven Member

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    Joined Feb 21, 2018
    Tucson, Arizona
    I have completely re wired the cas to the ecu using known good wires and soldering them together, to the same effect. I disconnected the ecu before swapping throttle bodies, and have tested multiple known good ecus as well. I suspected the CAS, so I replaced it to no avail. I have also tested the signal coming out of the cas and it appears to be working correctly. I’m using the 2Ga CAS that’s underneath the intake cam gear (which by the way is a pain to replace/adjust).
     

    Street Build 447  8

    1995 Mitsubishi Eclipse GST
    fwd · automatic · 2G DSM
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  2. motomattx

    motomattx Proven Member

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    wampum, Pennsylvania
    Are you showing rpm when you are cranking the engine? are you sure the wires arent backwards for the cas signal? Im running out of ideas.
     

    Drag Race Build 1K  13

    1995 Mitsubishi Eclipse GST
    fwd · manual · 2G DSM
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  3. Jacob_Barnes520GST

    Jacob_Barnes520GST Proven Member

    82
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    Joined Feb 21, 2018
    Tucson, Arizona
    I have rpm when it fires, but not when cranking. It has always been like that. I’m running out of ideas myself. I rewired the signal wire from the CAS and still the same thing. Maybe a CPS problem?
     

    Street Build 447  8

    1995 Mitsubishi Eclipse GST
    fwd · automatic · 2G DSM
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  4. Jacob_Barnes520GST

    Jacob_Barnes520GST Proven Member

    82
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    Joined Feb 21, 2018
    Tucson, Arizona
    I’m only getting 2.5v on the crank sensor signal wire. I’m getting 5v on the cam sensor wire. This is all wile the key is on not cranking. Is this normal?
     
    Last edited: Dec 1, 2018

    Street Build 447  8

    1995 Mitsubishi Eclipse GST
    fwd · automatic · 2G DSM
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  5. motomattx

    motomattx Proven Member

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    wampum, Pennsylvania
    Unplug the crank wire and then check it, if its still not 5v there is a problem.
     

    Drag Race Build 1K  13

    1995 Mitsubishi Eclipse GST
    fwd · manual · 2G DSM
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  6. luv2rallye

    luv2rallye DSM Wiseman

    7,408
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    Minneapolis, Minnesota
    2.5v is normal when not cranking (since there's a 5v voltage divider inside the ECU). When cranking you have pulses but you should read a voltage average between 0.4-4.0v (mine reads 2.4v).
     

    2K  0

    1999 Mitsubishi Eclipse GST
    14.200 @ 95.000 · 2G DSM
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  7. Jacob_Barnes520GST

    Jacob_Barnes520GST Proven Member

    82
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    Joined Feb 21, 2018
    Tucson, Arizona
    Okay then that rules out the wiring to the CPS and the CAS then. When I was cranking I had 2.4 volts at the CPS. I have a 1G CAS on the way with the adapter harness which will go on when it gets here. If the CPS and the CAS are tested good, what else could be the problem?
     

    Street Build 447  8

    1995 Mitsubishi Eclipse GST
    fwd · automatic · 2G DSM
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  8. Bleakley

    Bleakley Supporting VIP

    174
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    Joined Jan 29, 2017
    Pittsburgh, Pennsylvania
    Let’s stop shotgunning parts for a moment and get to the bottom of this one. Lol.
    I’m going to message you my number, text me, and we’ll get this sorted out.
    In the meantime, here are circuit diagrams for injectors, crank sensor, and cam sensor...

    8AD871B5-427B-4479-AA4F-07AEC86AF8C3.jpeg AE5FFECD-595C-4D8D-944A-24171E0173E3.jpeg DFA594D8-01DA-4231-BA55-61FCB0F322E9.jpeg
     

    Street Build 606  1

    1995 Eagle Talon TSi
    fwd · automatic · 2G DSM
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  9. motomattx

    motomattx Proven Member

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    wampum, Pennsylvania
    Not so, the 2.5 comes from the sensor landing on either a gap or a tooth and sitting there with the engine not running, the ecu chipset uses 5v logic circuitry.
     

    Drag Race Build 1K  13

    1995 Mitsubishi Eclipse GST
    fwd · manual · 2G DSM
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  10. luv2rallye

    luv2rallye DSM Wiseman

    7,408
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    Minneapolis, Minnesota
    Yes thanx, you are correct. I was thinking of the around 2.5v average you get when engine is running but I worded it all wrong. Also now looking again at the internal ECU circuit diagrams (for the CPS or CAS signal input) I see a tie up resistor to +5v and another resistor going off somewhere unknown, and I made an invalid assumption that it was a voltage divider. However the resistor going off is just a series resistor to other input circuitry - not a voltage divider. So the key on, engine not rotating voltage on the CPS (or CAS) is most likely either +5v or 0v depending on whether the Hall Effect sensor is opposite a gap or not gap (fyi not gap is a blade present section in the 2g CPS) as motomattx says.
     

    2K  0

    1999 Mitsubishi Eclipse GST
    14.200 @ 95.000 · 2G DSM
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  11. Jacob_Barnes520GST

    Jacob_Barnes520GST Proven Member

    82
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    Joined Feb 21, 2018
    Tucson, Arizona
    Thank you guys. Then that rules out the CAS and the CPS then
     

    Street Build 447  8

    1995 Mitsubishi Eclipse GST
    fwd · automatic · 2G DSM
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  12. Bleakley

    Bleakley Supporting VIP

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    Joined Jan 29, 2017
    Pittsburgh, Pennsylvania
    I’m still stumped where the 2.5 volts at rest comes in. Should be 0 or 5 at rest, no exceptions..
    Unplug crank sensor and voltage should be 5V. As said before, if not 5v there’s def something screwy going on.

    In my opinion. 2.5v plugged in, not cranking tells me there should be something wrong.
    Unless I’m missing something. A Hall effect sensor is nothing more than a switch. —> So if it’s not 5V or 0v when you test signal to ground. That tells me there’s current flowing and something’s taking my voltage away. Those resistors in the PCM have got to be some sort of current protection. Nothing more.


    Edit: I am not sure how the crank sensor signal’s input would shut off cyl 3 and 4 fuel when there not even a pair cylinder and we’re a waste spark setup. But I can’t imagine anything goin very well if the voltage signal to the pcm isn’t correct.
     

    Street Build 606  1

    1995 Eagle Talon TSi
    fwd · automatic · 2G DSM
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  13. Jacob_Barnes520GST

    Jacob_Barnes520GST Proven Member

    82
    7
    Joined Feb 21, 2018
    Tucson, Arizona
    Here’s good news

    I installed a 1g CAS and the adapter harness tonight, and it runs on all 4! I think when I installed the sensor I installed it out of time, because it sounds like the timing is retarded. Idles smoothly but stumbles when revved.
     

    Street Build 447  8

    1995 Mitsubishi Eclipse GST
    fwd · automatic · 2G DSM
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  14. motomattx

    motomattx Proven Member

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    wampum, Pennsylvania
    The ecu uses a pull up resistor on that input.
     

    Drag Race Build 1K  13

    1995 Mitsubishi Eclipse GST
    fwd · manual · 2G DSM
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  15. Bleakley

    Bleakley Supporting VIP

    174
    38
    Joined Jan 29, 2017
    Pittsburgh, Pennsylvania
    Pull up resistor? *learning*
     

    Street Build 606  1

    1995 Eagle Talon TSi
    fwd · automatic · 2G DSM
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  16. Jacob_Barnes520GST

    Jacob_Barnes520GST Proven Member

    82
    7
    Joined Feb 21, 2018
    Tucson, Arizona
    Small update. Car has a nasty boost leak, and still needs to be timed correctly after the new CAS was put in. Starts and idles, but has a nasty surge. I want to thank everybody that took the time to help me on this. I will post another update when it is back to normal.
     

    Street Build 447  8

    1995 Mitsubishi Eclipse GST
    fwd · automatic · 2G DSM
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  17. motomattx

    motomattx Proven Member

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    Joined Dec 9, 2010
    wampum, Pennsylvania

    Let’s say you have an ECU with one pin configured as an input. If there is nothing connected to the pin and your program reads the state of the pin, will it be high (pulled to VCC) or low (pulled to ground)? It is difficult to tell. This phenomena is referred to as floating. To prevent this unknown state, a pull-up or pull-down resistor will ensure that the pin is in either a high or low state, while also using a low amount of current.
     

    Drag Race Build 1K  13

    1995 Mitsubishi Eclipse GST
    fwd · manual · 2G DSM
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