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Thread: Cranks fine, won't start, fuel injectors not firing (?)

  1. #11
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    Default Re: Cranks fine, won't start, fuel injectors not firing (?)

    Q1: No voltage at CPS. The CPS generates its own voltage pulses.

    Q2: What you observe is normal for an off injector with ignition on.

    Power (12V) goes through the injector resistor pack and then to each injector. The white wires go to the ECU and are grounded (by a big power transistor inside the ECU) when an injector is commanded to fire.

    When an injector is off, the white wires are effectively open-circuit, and you will get no voltage drop across resistors or injector solenoids, hence seeing 12V on the white wires.

    Q3 A bad IGF signal will cut the injectors pretty quick, but you should see a few pulses before the ECU shuts them down.

    Sounds to me like you jumpered the wrong terminals when you did the diag test. The fuel pump comes on if you connect B+ to FP. You want to connect TE1 to E1 for diag. It must flash (every 0.2621 seconds) if no codes are set and TE1 jumpered to E1.


    If you remove the CPS and spin it by hand you should get spark with the ignition on.

  2. #12
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    Default Re: Cranks fine, won't start, fuel injectors not firing (?)

    Quote Originally Posted by 3p141592654 View Post
    Q1: No voltage at CPS. The CPS generates its own voltage pulses.

    Q2: What you observe is normal for an off injector with ignition on.

    Power (12V) goes through the injector resistor pack and then to each injector. The white wires go to the ECU and are grounded (by a big power transistor inside the ECU) when an injector is commanded to fire.

    When an injector is off, the white wires are effectively open-circuit, and you will get no voltage drop across resistors or injector solenoids, hence seeing 12V on the white wires.

    Q3 A bad IGF signal will cut the injectors pretty quick, but you should see a few pulses before the ECU shuts them down.

    Sounds to me like you jumpered the wrong terminals when you did the diag test. The fuel pump comes on if you connect B+ to FP. You want to connect TE1 to E1 for diag. It must flash (every 0.2621 seconds) if no codes are set and TE1 jumpered to E1.


    If you remove the CPS and spin it by hand you should get spark with the ignition on.
    What is "IGF"? I don't see any pulses at all.

    I may have jumpered the wrong ones. I will double check on that next time and make sure I do the right ones.

    I am getting spark when it cranks so I guess the CPS is working fine.
    Question - If I remove the CPS and spin it by hand with the ignition on, should the ECU send signals to the injectors to fire as well? Where does the ECU get its signal to fire the injectors?
    1987 Supra Turbo white (stock with 3" exh and K&N)
    1978 Datsun 280Z (first turbo'd, now supercharged, MegaSquirt, etc.)

  3. #13
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    Default Re: Cranks fine, won't start, fuel injectors not firing (?)

    I can see why the old timers get so disgruntled
    Getting old is mandatory, growing up isn't. --- Boostin Since 10/28/08
    13.4at105MPH/14PSI...The smell of cash is easily forgotten when all you smell is rubber.
    Be careful not to step in the bullshit.

  4. #14
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    Default Re: Cranks fine, won't start, fuel injectors not firing (?)

    Thanks for all your help guys, I've been really busy the last few days. I did try out a few things Friday afternoon, but nothing I did seemed to make a difference.

    I got the diags to work, and yes I was jumpering the wrong terminals.
    At first it didn't give any codes, just a continuous blink.
    Then after trying to start it a few times while pressing the accelerator, it gave me the "code 51", which is what dumbo said it would do.
    After resetting it, it threw another code, this time "code 11" - I am 100% sure it was code 11, but I can't find any indication of what that could could mean. It's not listed in the PDFs, does anyone know what it means?

    I think I had some of the vacuum hoses hooked up wrong, and I believe I corrected that. Is there supposed to be a VSV between the intake maniold vacuum source and the fuel pressure regulator? That's what the diagram under the indicated, and it said there's supposed to be another VSV for the EGR system. I think I only have one VSV, not two. And it has a 2 pin connector (red) that plugs into the wiring harness. Does this go to the EGR system or does it go to the FPR?

    I don't think any of this is part of the problem, since I have confirmed that the issue is that the "injectors are still not firing", but I'm sure it would be better if I got the vacuum hoses hooked up correctly.

    Any ideas on the injectors? Should I try a different ECU?
    1987 Supra Turbo white (stock with 3" exh and K&N)
    1978 Datsun 280Z (first turbo'd, now supercharged, MegaSquirt, etc.)

  5. #15
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    Default Re: Cranks fine, won't start, fuel injectors not firing (?)

    code 11 is interuption to ecu B+..i belive.
    1.Main Relay Circuit
    2.Main Relay
    3.ECU
    Not sure why its not on the TSRM Online, its in my 86.5 TSRM(Actuall Book)
    I would check the "EFI Main Relay" and "EFI" fuse, but i think the fuse should be fine if your diagnostics work, also check the circuit wiring-not sure though.

    http://cygnusx1.net/supra/Library/TS...aspx?S=FI&P=29


    Your right there is a VSV for EGR and FPR, netiher well cause your car not to start, and the tsrm explains how to check them and how to route vacum lines/electrical.
    Getting old is mandatory, growing up isn't. --- Boostin Since 10/28/08
    13.4at105MPH/14PSI...The smell of cash is easily forgotten when all you smell is rubber.
    Be careful not to step in the bullshit.

  6. #16
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    Default Re: Cranks fine, won't start, fuel injectors not firing (?)

    Well, that definitely seems like it could make the injectors not fire :-)
    I don't know why code 11 isn't listed in the PDF TSRM. That will be my next step then, I'll follow the instructions on page FI-33 for checking the EFI Main Relay.Thanks dumbo!
    1987 Supra Turbo white (stock with 3" exh and K&N)
    1978 Datsun 280Z (first turbo'd, now supercharged, MegaSquirt, etc.)

  7. #17
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    Default Re: Cranks fine, won't start, fuel injectors not firing (?)

    It would be highly unlikely that you would get spark and no fuel if it really was a B+ issue. Check the ECU grounds at the intake manifold, they need to be tight. Measure the voltage drop across them with the ECU on (should be small voltage, much-much less than 1 V.

    Is the battery getting weak from all the cranking? If so, that can give a B+ error.

    How are you concluding the injectors are not firing? At low speeds the duration is pretty small, so a regular voltmeter won't be helpful.

  8. #18
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    Default Re: Cranks fine, won't start, fuel injectors not firing (?)

    I replaced the EFI Main Relay, and the error code does not persist. Engine Diags read all clear (continuous flashing when jumpered). There is power at B+ with IGN SW ON.

    Battery is brand new and strong, I hook it up to a running car with jumper cables while I am running tests to keep the battery charged.

    I am using a Noid Lite to determine the injectors are not firing. It is not flashing or lighting up at all. There is power to the injectors.

    When it first cranks there's a puff/short series of combustions and then whenever I feather the throttle while cranking there can be a short burst of combustions, but none long enough to keep it started. My thought is that a small amount of fuel is being introduced by the Cold Start Injector, but no fuel is coming from the 6 main injectors.

    Next, I am going to try a new ECU, unless someone can give me something to test that might be causing this situation: Spark is there but injectors are not firing.

    PS: The online TSRM is for a 1990, that may explain the missing Code 11.
    1987 Supra Turbo white (stock with 3" exh and K&N)
    1978 Datsun 280Z (first turbo'd, now supercharged, MegaSquirt, etc.)

  9. #19
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    Default Re: Cranks fine, won't start, fuel injectors not firing (?)

    Quote Originally Posted by Brazle View Post
    The ECU gets reset everytime I leave the car because I disconnect the battery.
    Reset to what? Just wondering.

    Quote Originally Posted by Brazle View Post
    What is "IGF"? I don't see any pulses at all.
    http://www.autoshop101.com/forms/h23.pdf
    Have you loosened Orion's belt yet? The opposite of right is both left and wrong.

    http://www.thereligionofpeace.com/

  10. #20
    90T
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    Default Re: Cranks fine, won't start, fuel injectors not firing (?)

    Do you see 12V at the STA terminal at the ECU when cranking? That should initiate an asynchronous pulse of all six injectors during cranking. You should also confirm that the fuel pump is getting 12 V during cranking by monitoring the FP terminal in the diagnostic box with a voltmeter.

    An IGf problem will set a code 14, moot given that spark is being confirmed by the OP.

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