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500, 472, 425, 368 Discussion, Engine will not turn back on if hot in Cadillac Engine Technical Discussion; Originally Posted by BRUCE ROE GORNATI, The air temp sensor is in a runner from the carb to a cylinder. ...
  1. #16
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    Re: Engine will not turn back on if hot

    Quote Originally Posted by BRUCE ROE View Post
    GORNATI,

    The air temp sensor is in a runner from the carb to
    a cylinder. The water temp sensor in the coolant
    somewhere; I've seen them at the thermostat or in
    the back pipe to the heater. They are interchangeable,
    should measure around 1000 ohms at room temp. If
    only one is good, make sure it is in the water till you
    get another.

    I don't charge to check out your ECU. But postage &
    customs could be a problem here. Most ECUs need
    something; I usually recommend getting them checked
    so you can cross it off the problem list. If your
    pulse widths are OK, the MAP is probably OK too.
    Keeping a spare ECU can help, though people that
    far away sometimes just give up the fuel injection and
    put on a carb.

    I'm retired, advisor to the CLC (Cadillac LaSalle Club). I
    think their web site is under construction for a few days.
    I don't often sell ECUs, but if I had your model, it
    would be a small fraction of the $350 the Ebay guy
    wants. Don't know who that is, I wonder if he can
    test & repair them as well as I do?

    Lots of ECUs are marked "REMANUFACTURED". Not
    to worry, they are OK but renumbered. If you give me
    your email, I can send a list of ECUs and what they fit.
    And my EFI checklist. I'm bcroe@juno.com

    The usual problem with mixture, is a failing MAP
    sensor in the ECU. If it is putting out low voltage
    now, it will soon fail completely. Its on picture 10
    (SH 8) of ALBUM-78 K ECU SCHEMATIC. Notice
    that there is a test point VMAP where you can measure
    the MAP voltage, a 5 pin connector on the side. Or with
    ignition on but not running, no hose connected, you
    can remove the cover and and measure the MAP voltage
    at its pin, or wire jumper 13. It should be 9.5V input,
    7 to 7.5V output. The 7V will drop to 0-2V as vacuum
    is applied. The hose to the ECU connects to the MAP.
    If it is failing, I could install one of my replacements.

    Once the engine is hot, your ECU should put out a
    fuel injector pulse width around 4ms at idle, 8 ms at
    cruise, and near 12ms at Wide Open Throttle.

    deVille33 also gives good advice. Most cars that age
    should get a new timing chain; the original cam sprocket
    has plastic teeth which fall off, block oil flow, and let
    pistons hit valves. You can check it without taking the
    engine apart.

    good luck, Bruce Roe
    Yesterday i found what looks like a loose sensor, will take a picture and post it here, then i will check them sensors.

    My ECU is indeed remanufacturated, but im thinking about getting another one, just in case.

    I sent you an email so you can send me that info you offered, i accept it

    After the eletrical part is ok, i will start checking the timming, belts and cam sprocket.

    Im taking notes of everything you guys told me so far, my first daughter is about to born, so i dont think i will have the time to do everything in the next 2 weeks, but i keep you all posted.

    Thanks

    C. Gornati

  2. #17
    deVille33 is offline Cadillac Owners Connoisseur
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    Re: Engine will not turn back on if hot

    Eliminate which relay? sorry if it seems a dumb question...[/quote]




    No dumb question. Above the brake pedal and to the right, there is a board with several relays attached to it. You will find an area in the top left corner which is burned out. Your fan / temperature control relay used to plug in there.

    Your fan circuit goes to a series of coils up in your air control box, which sense the temperature of your air box and determine fan speed. The signal goes back to the relay and switches the circuit from high to low, so your temperature control is automatic.

  3. #18
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    Re: Engine will not turn back on if hot

    Just a quick update wich may give some information for you guys help me..
    Sorry for being a little indivdualist on this one...

    Well, my camera has no batteries, while they are charging, i decided to go out and drive around the block with the caddy.

    Turn the car on, start at the first turn of the key, idle is extremmly high, i have no tachmeter, but looks like it is between 1500 and 2000 rpm.

    Car is cold and when i pump it looses rpm and almost dies, if step on the gas it will shut off (any ideas?)

    Left the car running for almost 8 minutes, then idle goes to normal i am able to pump on the gas and the car will not die, did the maneuver to take the car off the garage, i live in an apartment and the biggest car here is a ford ranger, it is very hard to remove the car.

    After that iam able drive in the neighbordhood, car runs good, could not get a lot of speed, brakes are not 100%, i would say stopping power is about 15% now...

    So the question is, what could be causing the car to have such a high idle and not be able to pump on the gas when the car is cold?

    After is hot, idle is normal and runs like a deer...

    Will take some pictures of what i think it is a lose sensor and pictures of some wiring i found disconnected.

    Again thanks you all

  4. #19
    BRUCE ROE is offline Cadillac Owners Fanatic
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    Re: Engine will not turn back on if hot

    Did you check the sensor resistance yet?

    Your idle speed is controlled mostly by the COLD IDLE AIR VALVE, shown in the PHOTOBUCKET site. Pushing down on this should slow the engine some. Bruce Roe

  5. #20
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    Re: Engine will not turn back on if hot

    Will get the new pics, tonight.

    Thanks Bruce.

  6. #21
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    Re: Engine will not turn back on if hot

    Well finally had the time to take some pictures...

    Here is what i think it is a sensor, if it is a sensor, what sensor is this?

    This is located right before the cruise control, diaphragm.



    I dont know, things are slow now here, still need to get the licence plate to take the car to be washed down and have the brakes done.

    So, little by little you all help me out.

  7. #22
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    Re: Engine will not turn back on if hot


  8. #23
    BRUCE ROE is offline Cadillac Owners Fanatic
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    Re: Engine will not turn back on if hot

    You mean, that disconnected cable from the cruise control? Bruce Roe

  9. #24
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    Re: Engine will not turn back on if hot

    so, not a sensor at all?

  10. #25
    BRUCE ROE is offline Cadillac Owners Fanatic
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    Re: Engine will not turn back on if hot

    Follow it back, does it go to the cruise control unit? Bruce

  11. #26
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    Re: Engine will not turn back on if hot

    well bruce, your dang right, the thing i think it was a sensor is the cruise control link.

    today i drove the car for a while, brakes are terrible, but after filling up the tank, engine died, but easily turn back on.

    I think that could be some old gas and dirt on the lines also.

    today i also redone the center panel wich was disasembled.

    Next week i might already have the new brake booster and master cilinder, after that with brakes will be much more easy to take the car to shops and fixing all the stuff.

    Today is mothers day here in brasil, so i had a very shor time to mess with the car, next saturday will be good, i will wash the car, fix some eletrical problems.

    Regards to you all.

    Thanks again Bruce and DeVille33

  12. #27
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    Re: Engine will not turn back on if hot

    bruce and deville, please check this other topic.

    http://www.cadillacforums.com/forums...y-service.html

  13. #28
    BRUCE ROE is offline Cadillac Owners Fanatic
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    Re: Engine will not turn back on if hot

    You haven't checked the temp sensors, the MAP sensor, of the cam sprocket yet. Bruce Roe

  14. #29
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    Re: Engine will not turn back on if hot

    Well i honestly didnt do my homework, i will re read the topic and check those sensors on saturday.

    but i am a little affraid to test the ECU, im afraid to burn the whole thing.

  15. #30
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    Re: Engine will not turn back on if hot

    Hey Bruce how much for the MAP replacement circuit?

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