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Thread: Thermostat time switch unplugged - Cranks but no start?

  1. #1
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    Thermo time switch unplugged - Cranks but no start?

    Ok, more curious then any problem but why would an unplugged thermo time switch in the cold start circuit cause a no start. The starter will crank and crank but no hint of starting? Plug it back in and it pops right off.

    You would think since it was 76F out and the car was driven in the last 6 hours that it wouldn't need the cold start injector to be adding gas to start the engine.

    The engine temp was 80F based off a temp gun's lazor beam pointed at the housing of the thermo time switch.
    Last edited by msiert; 06-08-2019 at 05:46 PM.
    Murray

  2. #2
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    80F is a 'cold' engine.

    There's a temp rating on the switch. Mine (1978) is 35C = 95F.
    Tbd

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    Do you have spark

    Sent from my SM-G960U using Tapatalk

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    Rating is 35C 8 seconds, (95F) so yes this should trigger the cold start injector which is what I was working on to test but I was just surprised that with the thermo time switch unplugged that would cause a no start.

    When I turned the key to start the engine the starter turned the motor over quickly but that's all it did. It did act like it wasn't getting any spark (didn't check through) but how could that be caused from an unplugged thermo time switch on the cold start circuit?

    i read that some have tapped into the brown line to that switch some how to be able to control the cold start injector manually but again it seems like that plug is part of the starting system and unplugged will not start.

    Just came to me, if the engine's temp would have been over 35C it would have started with it unplugged, right?
    with the temp technically cold the signal to start goes through the Thermo time switch and with it being unplugged it won't start?
    Last edited by msiert; 06-08-2019 at 10:27 PM.
    Murray

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    Either way cold or hot the starter sends power to the thermo time switch through the diode relay, depending on the temp, if cold, the power get transmitted to the cold start injector for a certain time period depending on the temp. Don't recall that power being sent on to any other component in the start circuit? Will have to look at the wiring diagrams again to see forsure.
    Last edited by msiert; 06-08-2019 at 10:25 PM.
    Murray

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    If it doesn't start over ~35C (assuming tts and cold start injector is good), then this could simply mean that the fuel mix is adjusted a tad too lean (also assuming wur is proper and no vacuum leaks, good sparks, etc.). Fun experiments
    Last edited by epmedia; 06-08-2019 at 10:49 PM.
    Tbd

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    Quote Originally Posted by msiert View Post
    Either way cold or hot the starter sends power to the thermo time switch through the diode relay, depending on the temp, if cold, the power get transmitted to the cold start injector for a certain time period depending on the temp. Don't recall that power being sent on to any other component in the start circuit? Will have to look at the wiring diagrams again to see forsure.
    81-83 electric manual if you need a copy for further understanding/experimentation:
    http://www.findmymerchant.com/images..._1981-1983.pdf
    Last edited by epmedia; 06-09-2019 at 01:36 AM.
    Tbd

  8. #8
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    Cold Start Valve is wired to the starter, so when the starter is engaged the CSV streams additional fuel in, CSV is tied in too the TTS as well so if it not connected no additional fuel,, additional fuel enriches the air/fuel mixture for easier startup, all cars like a rich start up.

    Randy

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    My car every now and then needs a shot of staring fluid to get it to kick over in the state your describing not cold not hot engine. I documented that the switch is good below.

    https://www.bimmerforums.com/forum/s...0#post30175830

    scroll to bottom I have my results of the resistances of the TTS

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    Thanks epmedia for the wiring diagram and Randy and 82 Kashmir for the help, looking at it I see no reason for the car not being able to start other then it really needs that extra shot of fuel from the cold start injector.

    The problem I am having is the engine fires right up but right afterwords the idle dips to almost stalling then comes back up, does this a couple of times then all is fine. Durning this up and down I get some white smoke out of the exhaust.

    If I make the mistake of giving it any throttle at all durning the starter cranking I get a lot of white smoke and a lot of stumbling.

    If I give it some gas durning the stumbling it clears up and all is fine.
    Last edited by msiert; 06-09-2019 at 11:41 AM.
    Murray

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    The white smoke does not have a sweet smell or fuel smell to it more of an acidic smell if that would make any sense?
    Murray

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    Very helpful link 82 Kashmir, thanks
    Murray

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    Quote Originally Posted by 82Kashmir View Post
    My car every now and then needs a shot of staring fluid to get it to kick over in the state your describing not cold not hot engine. I documented that the switch is good below.

    https://www.bimmerforums.com/forum/s...0#post30175830

    scroll to bottom I have my results of the resistances of the TTS
    Here is my test results: Cold 77F

    G to frame......65 ohms

    W to frame......30 ohms

    G to W...…...62 ohms

    What it should be: (below 30C)

    G to frame......25 to 40 ohms

    W to frame......0 ohms

    G to W...…...25 to 40 ohms

    Looks like it's a goner, huh?
    Last edited by msiert; 06-15-2019 at 11:36 AM.
    Murray

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    The TTS bi-pass till I decide if I want to buy a new TTS. The engine does start quicker, less cranking time then before, like one revolution, pop she fires.
    Attached Images Attached Images
    Last edited by msiert; 06-09-2019 at 08:11 PM.
    Murray

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    White smoke is most likely condensate, the catalytic converter gets quite hot and as it cools down moisture from the air settles in and then evaporates from being heated up--white smoke from the exhaust .

    Randy

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    The cheapest TTS I found was at Rm European for $160 all the other vendors were either sold out or over $200. Looks like they don't have any of the original sized (shorter) TTS, the replacements are a new design that are taller, think it will still work, hope so?
    Murray

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  18. #18
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    Exact Match from Greece thru ebay 119 +10 Shipping

    s-l64.jpg


    https://www.ebay.com/itm/BMW-E30-E21...frcectupt=true

    Randy
    Last edited by 320iAman; 06-09-2019 at 09:31 PM.

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    Oh man!
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  20. #20
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    Quote Originally Posted by msiert View Post
    The TTS bi-pass till I decide if I want to buy a new TTS. The engine does start quicker, less cranking time then before, like one revolution, pop she fires.
    I use a momentary push button on the dash. Be sure to disconnect that bypass wire when the engine is warmed-up (that is, if the engine denies that extra squirt of fuel when turning the starter motor).
    Tbd

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    Quote Originally Posted by msiert View Post
    The cheapest TTS I found was at Rm European for $160 all the other vendors were either sold out or over $200. Looks like they don't have any of the original sized (shorter) TTS, the replacements are a new design that are taller, think it will still work, hope so?
    Mine stopped working properly and did not do anything between 50-80F and it was very hard to start the engine. I purchased the new Genuine BMW TTS for around $200 and it solved all the problems. It is taller than the original but works fine. Make sure to use supplied crush ring so it does not leak.

    Max

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    I think I might have one lounging about that still works. It’d at least get you by until you have a new one
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  23. #23
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    Quote Originally Posted by msiert View Post
    Here is my test results: Cold 77F

    1) G to frame......65 ohms

    2) W to frame......30 ohms

    3) G to W...…...62 ohms

    What it should be: (below 30C)

    G to frame......25 to 40 ohms

    W to frame......0 ohms

    G to W...…...25 to 40 ohms
    [/LEFT]

    Looks like it's a goner, huh?
    For experiment, I was checking mine ~84F (~29C)
    1) 35 ohms
    2) 0 ohms
    3) 35 ohms

    I never tested it before and was thinking that if mine had bad readings, I might 'cycle' it in and out of the freezer a few times to attempt getting the readings within spec. I believe that 'W to frame' is a mechanical connection. Something else to experiment with

    *looking at your readings, that extra ~30 ohms on all your readings is probably because of that "W to frame' resistance.
    Last edited by epmedia; 06-10-2019 at 06:34 PM.
    Tbd

  24. #24
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    Quote Originally Posted by epmedia View Post
    For experiment, I was checking mine ~84F (~29C)
    1) 35 ohms
    2) 0 ohms
    3) 35 ohms

    I never tested it before and was thinking that if mine had bad readings, I might 'cycle' it in and out of the freezer a few times to attempt getting the readings within spec. I believe that 'W to frame' is a mechanical connection. Something else to experiment with

    *looking at your readings, that extra ~30 ohms on all your readings is probably because of that "W to frame' resistance.
    Hi Robert ...

    I was having similar thoughts. Since there is nothing to lose by trying a few things first, I had the same idea about cycling the switch in the freezer a few times. But there are other things you can try too. First I'd try just giving the W connector pin on the outside a quick check. They come from the factory nickel plated to resist oxidation ... but over time they can build up a film. If you measure from one flat to the other on the W pin it should give you a 0 voltage drop across it if you use the Continuity/Diode test function or whatever the resistance of your test leads are on your low ohm setting on your multimeter.

    I've re-jigged a drawing I've posted here before to show the possible "bad" contact points inside the original style TTS. It's a fairly simply bi-metallic strip type switch and the most likely place for there to be an "extra" 30 Ωs would be either across the main switch contacts or where the fixed contact connects to the housing or to the W connector itself. Subtracting 30 Ωs from the other readings you got brings them back ito the "normal" range.(I suspect calling the body/case/housing the "frame" is one of those literal translations from the German things).

    If the problem is one of these .. then there is not a lot that can be done .... but there is a calibration screw in the side of the housing, so it may be possible to adjust it back to a working condition.
    Bi-metalic switches when they operate over a narrow temperature range can sometime develop a "set" that distorts their shape a bit and changes how they bend with changes in temperature and it may be stopping the switch closing properly and giving a high resistance reading.

    I would start by seeing if lowering the temperature can lower the W to "frame" resistance. Sticking the sensor part of the TTS in some ice water should be enough for testing purposes.
    If it does then get it back to the normal 0 Ω temperature range and see if you can adjust it back to 0 Ωs. If it doesn't then go all out freeze it!

    When I dug out my spare to do the photo .. I had a little play with the adjusting screw just out of curiosity and it turns with a bit of resistance, not sure which way to turn it .. so it will be a bit of trial and error. oh .. mark your starting point .. it makes it so much easier if you go the wrong way first.

    Hope some of this will help ...

    Cheers

    Graham D

    oops .. a little PS:

    The newer "long" type TTS is a replacement for the old type but it is electronic and can't be tested by measuring resistances!
    Without knowing what the circuit is inside, the only way to test it is to use a test light or pull the cold start injector to see if it works for the right amount of time for the temperature when it is powered up.
    Attached Images Attached Images
    Last edited by GDAus; 06-11-2019 at 01:38 AM. Reason: Added info
    hmm .. Wonder what happens if I do this ...

  25. #25
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    That, sir - is pure gold. Until now, I was not aware there was even an adjust screw, I thought the dimple was just a 'pinch'. Mine (2/78) has a plug/cover where the screw is on your picture.

    * brings me to another thought... maybe it's possible that someone has tampered with Murray's tts screw (if the plug/cover removed).
    Last edited by epmedia; 06-11-2019 at 02:36 AM.
    Tbd

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