S30Grit

280Z Requires Starting Fluid for Cold Starts

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    Hi All,

    I'm new to the forums and recently acquired a 280Z!  I'm really excited about the car, but I did make the purchase with it not running.  The interesting (and very bizarre) issue I'm having is that the engine refuses to start on it's own when it's cold.  The weird part is that with a quick spray of starting fluid (3 sec), the car starts up and RUNS instantly and idles/revs using it's own EFI without problem.  If I leave the engine idling for a couple minutes (not even up to op. temp.), then kill the engine, it will subsequently start on it's own without the need of starting fluid.  It appears to only be cold starts where the car refuses to start on it's own.  After letting the engine fully warm up, I can start the engine just fine several hours later without starter fluid.  But fully "cold" starts it will always fail without starting fluid.

    A trusted mechanic and myself have tried several things, and consulting the FSM as well.  I'll be working more thoroughly through the full EFI troubleshooting FSM this weekend to make sure we haven't missed something.

    During a failing cold start, what is known:

    • Fuel pressure is correct/consistent at the fuel injectors during priming and starting sequence
    • Spark is present
    • Timing of the engine seems fine once it's started/idling via spray
    • Fuel Injectors simply appear to NOT be receiving a signal to fire during startup (in-line light test was done). [obvious red herring here].  The weird part is that obviously after the starter spray is used and the engine starts, the fuel injectors start working.

    Previous owner and myself have thrown a few new parts at it without necessarily diagnosing each component: Spark plugs/wires, starter motor, battery, fuel pump/filter/regulator, some vacuum hoses.

    Troubleshooting done already, that has not changed the symptoms:

    • Swapped in a different ECU (although I did notice that the ECU part number appears to be for an automatic A11-601000 while the car is a manual.  But after reading, apparently the ECU's are actually the same)
    • Cleaned misc. electrical connections everywhere I can think of (although I know I'm missing some areas)
    • Checking fuses and fusible links
    • Swapped in new EFI relay
    • Unplugging a few sensors/connections to remove those variables (typically in isolation): thermotine, temp sensor, CSV.  My understanding is that regardless of this configuration, the injectors should be getting a signal to fire on startup anyways though.

    Seems like an electrical gremlin, but running out of ideas to kill it, other than hooking up a NOS system as my starter fluid (kidding).  I'll be spending a lot of time with the multimeter it seems, but any ideas what component/wiring could cause this?

    Edited by S30Grit

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    the only happens when cold is odd, exactly how cold is it where you are?

    Have you confirmed the CSV is operating IF the temps are indeed cold? generally it is not turned on unless its less that 70f?

    Try listening for the injectors rather than looking at lights. I used a stethoscope.

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    If it were me, the first thing I would check is the cold start valve and thermotime switch. If you pull the cold start valve harness and connect positive and negative to the two cold start valve terminals, does the cold start valve spray? If yes, and you manually spray the cold start valve when the car is cold, does it start?

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    Thanks for the quick responses.  I'll definitely check out each of these things this weekend.

    It's been 80+ F where I'm located at (SF bay area).  Maybe a dumb question: Is it correct to assume that the CSV is only used in conjunction with the normal injectors? i.e. never in isolation?  I didn't see this operation described in the FSM.  If CSV and normal injectors are only used simultaneously, then I'm still very puzzled why the injectors aren't getting signaled to spray on cold starts.  The mechanic used a specialty light for injectors (not a simple test light), I can try listening to the injectors but I'll expect a similar result. 

    This weekend will be more chilly, below 70F in the morning for sure.. either way, I'll see if the CSV is 1) getting signal to spray and 2) actually spraying. And depending on those results, 3) manually triggering the CSV to spray and attempt to start.  I won't be expecting the ECU to trigger it to spray if the coolant is above 70F, like Dave WM said - which could point to a water temp sensor issue if I'm not mistaken.

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    I think it would be a good idea to take a pic of the driver's side of your motor and post it.  It's amazing what will "jump out" at these guys if it's wrong.  I'm mainly wanting to see how your AAR hoses are routed.  In '78 Nissan changed it around to keep some gunk out of the Auxiliary Air Regulator like this picture.  That thing keeps the idle high until it warms up then closes off the extra air and then the idle drops.  Here's a shot of the bullet connectors that get plugged up wrong a lot of times too.  

    Welcome to the forum!  You won't find a nicer or more helpful group.  

    image.png

    bullets.jpg

    tempsensor.jpg

    Edited by siteunseen
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    Sure thing, here's two images.  I'll take a closer look at your image and compare, but first glance looks ok?  And yes, mine is a '78, hopefully plumbed up like one.

     

    1.jpg

    2.jpg

    • Like 1

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    3 hours ago, S30Grit said:

    I won't be expecting the ECU to trigger it to spray if the coolant is above 70F, like Dave WM said - which could point to a water temp sensor issue if I'm not mistaken.

    The ECU has nothing to do with the CSV.  The CSV system is its own little separate control system, with power supplied to it and controlled via the thermotime switch.  No ECU involvement, no coolant temperature sensor involvement.  There is a "signal" that supposedly goes to the ECU, in the diagram, but many of us have realized that the ECU's don't have a wire to that pin.  It seems to be a diagram mistake that Nissan never fixed.  The thermotime switch is a thermally actuated relay that grounds through the switch body.  Check the ground circuit.  The wiring diagram can be confusing if you don't know that.  There is power through a heater wire around a bimetallic strip, that opens and closes the relay contact points, and also power to the CSV injector. It's pretty ingenious but still looks crude.

    I removed my CSV and had delayed starting when it got colder or the car sat for a while.  So I changed my starting procedure to giving the engine a good 5 or 6 revolutions on a first crank then letting it sit for about 20-30 seconds so the gasoline from the injectors could vaporize.  Then it typically would start normally.  You might try that as a test for or as a way to get by without starting fluid.

    image.png

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    Also, I never realized this and don't know how it's done, but, apparently, the thermotime switch is adjustable.  Weird.

    image.png

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    4 hours ago, jonathanrussell said:

     

    don't think its adj just a range that it happens to operate in. I know you can buy different spec ones, I got one for a VW that operates up to 85f

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    Yeah, sorry about the pic.  Photo was taken a few days ago during troubleshooting.  Definitely had the issue regardless if the CSV was connected or not.  Either way, I'll be sure to do some more tests on the CSV soon.

    Zed Head - thanks for the clarification, that's very interesting it's an independent system.  I'll try that starting procedure to see if I have any luck.  There's definitely been some starting attempts, waiting various amounts of times, and trying again with no luck.  I'll give that timing a try tho.

    However, given that it will fail to start in 80F weather, doesn't that mean it's likely not a CSV issue?  I'm still operating under the assumption of this question: "Is it correct to assume that the CSV is only used in conjunction with the normal injectors?"  

    Still extremely puzzled why injectors refuse to fire when engine is cranking regardless of CSV, thermotine, etc... not to say it's not the cause, just having trouble putting the pieces together.

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    I had a problem once with a weak, not completely bad, ignition module.  The spark was too weak during starting to fire gasoline, but would fire on starting fluid.  Once it started it seemed to run okay,  Probably low voltage during starting through a weakened ignition module.  The module has to have good current through it to create good spark.  I damaged the module by leaving some spark plug wires disconnected and starting the engine.  Forgot to say that I did change the module to a new HEI module once I figured out that it was weak spark.  Orange, not blue.  The new module fixed it.


    So, if you're still baffled, trying the HEI module swap might be worth a shot.  Pretty cheap and you can wire it up under the hood using spare wire pretty easily, as a quick test.  These old modules die on a regular basis anyway, yours will eventually.  Might as well be ready.

    Edited by Zed Head

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    Ahhh, I knew I forgot one thing on the "new parts list".  It has a brand new ignition switch assembly btw.  I didn't install it, so maybe I'll re-check the wiring.

    Spark could be an issue, but I know fuel is an issue (99% sure at least) since the injectors aren't putting fuel in during cranking.  

    Is the OEM 1978 module HEI? I'll have to do some research, is there specific part/manufacturer you recommend?

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    1 hour ago, S30Grit said:

    Spark could be an issue, but I know fuel is an issue (99% sure at least) since the injectors aren't putting fuel in during cranking.  

    If you're absolutely positive that the injectors aren't opening then that should be your focus.  Check the Pin 1 circuit at the ECU.  Maybe it has too much resistance or something weird happens during starting.  Pin 1 is connected to the negative terminal of the coil so the ECU can "see" when the coil fires.

    On the module don't assume that new is good.  1978 does have "HEI" but the module I was talking about is the GM HEI module swap.

     

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    3 hours ago, Zed Head said:

    I'm just reading the words in the FSM.

    prob something got lost in the translation.

    use a stethoscope and listen to the injector while it is running so you will know what it should sound like, then try it again when cranking.

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    Do you have a volt meter?

    If so:

    1. Check the battery voltage

    2. Check the battery voltage when cranking

    3. If it's low when cranking add a second battery with jumper cables or a jump box would be even better. Let's rule out low voltage possibilities to start with

    If you do not have one, consider going to Harbor Freight and getting a cheap one. It will make diagnosis much easier

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    Mr.Grit:

    Well, you've certainly been given a whole bunch of issues to attack, eh? That's called "mental dazzle", and is the enemy of a methodical approach.

    If I may be so bold, I would suggest that since you know the injectors work just fine, the logical place to begin is with the Cold Start Valve. When you look it up in the Shop Manual, you will see that it is itself, a single injector mounted in the intake tract before the manifold.

    It's job is to act as an electronic choke that enriches the starting mixture for a "cold" (a term that has more to do with engine temperature than air temperature) engine. It is controlled by the Thermotime switch, much like a choke pull-off.

    Your job is to first see whether or not it is squirting at startup, usually by dismounting it (still connected electrically) and aiming it into a jar while someone starts the car, as the Manual directs.

    If it squirts (which I doubt), you can check it off the To-Do list.

    If not, the fun begins. The Manual will guide the way.

    Bon chance

     

     

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    There definitely hasn't been a shortage of ideas, which is much better than the alternative!  Gives me plenty of things to check.

    The main question I have right now is regarding the CSV.  If the CSV is used during startup, is the computer not supposed to pulse the injectors?  Just good to know what the expected behavior is.  I didn't see anywhere in the FSM describing if the car is supposed to use the CSV AND the injectors while cranking.

    If car is supposed to only use CSV or injectors: very likely a CSV/thermotine related issue.

    If car is supposed to use both fuel methods: I'm looking at some much tougher troubleshooting.

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    15 minutes ago, S30Grit said:

    The main question I have right now is regarding the CSV.  If the CSV is used during startup, is the computer not supposed to pulse the injectors? 

    It's a good question and maybe Nissan had a plan for that.  Easier to just measure what's actually happening though.  As I mentioned above my engine started with no CSV at all.  If the injectors weren't squirting there'd be no gas to start with.  And there are no pins to the CSV or thermotime switch to the ECU.  So, no way for the ECU to "know" if it's squirting.  I think that the CSV is extra, added on top of injector fuel.

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    Ahh, good point, seems then that CSV alone likely isn't the cause then. But it's easy to test so I'll check it out. 

    Im swapping the injectors right now because one is seeping gas, and a bit of a safety harazard. More to come... 

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    The cold start spray is in addition to the normal injector squirting. Both the regular injectors and the CSV will spray at the same time if the engine is cold enough.

    So, I got a question.... When you say it won't start without a spray of starter fluid, how long are you cranking it for before saying it "won't start"? Reason I ask is that I removed my cold start valve completely and it definitely takes longer to start without it than it did before I took it off. Maybe five seconds of cranking? I'm wondering if you just are giving up too soon.

    What happens if you crank the engine for fifteen seconds straight? Sounds like a short amount of cranking, but with your hand on the key, it doesn't feel like a short time.

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    Next time try this when its cold.

    disconnect the starter solenoid spade connector (this disables the starter), Turn the key to start and count to 5, release from start position and reconnect the starter solenoid connecter, now try to start it. If it starts right up this way then you have something causing the fuel to drain back out of the lines, requiring the pump to run a extra long time to build pressure. Normally the pressure will come up from 0 to 36 psi in about 2 seconds (not long enough to notice during starting). If the lines are completely empty of fuel it will take much longer as you have to fill the filter and all the lines. The completely empty scenario should NOT happen, but maybe a faulty drain back valve could cause it. A proper operating pump will fill the system but will take the extra few seconds to do it

     I notice that if I drive every day the start is nearly instant, if I take a week off it takes an extra 2-3 seconds.

     

    BTW, you may hear a "CLICK" sound under the hood when you turn to start, that would be the CSV IF its cold enough to activate. It almost sounds like a loud spark, so do be concerned if you do hear it.

    Edited by Dave WM

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    Dave, I was thinking the same thing, but the OP said this:

    On ‎10‎/‎17‎/‎2019 at 12:20 AM, S30Grit said:

    During a failing cold start, what is known:

    So it sounds like he already confirmed that the check valve is holding and the fuel pressure is OK even while the problem is occurring.

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