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Thread: Does a 750 start with engine oil level low warning?

  1. #1
    Join Date
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    11/88 E32 750iL+98 E36M3

    Does a 750 start with engine oil level low warning?

    question to the electronic wizzards (just want to know, as I am not sure about this):

    First of all: There are TWO engine oil level contacts on the M70 (maybe also on the other engines).

    static contact
    and
    dynamic contact

    In case the oil level is sufficient, the static contact is closed.
    Via the ground signal the check control get's to know that the level is o.k.
    The dynamic contact is open, the control voltage flows against ground.
    In case the oil level goes under the dynamic switch point, a message comes.
    That the oil flowing into the oil pan when engine is switched off does not delete the alarm, the fault is stored with terminal 30.
    It will only be deleted, when the static contact reports a message/signal, that the engine oil is filled up to static level.

    The wires to the static contact are also checked for wire problems by the system of the car.
    After ignition is switched on, a oil level warning will come. After starting to drive, but latest after 20 seconds this warning will disappear.

    The wires go thru the pipe in engine room left side together with the thick wire from alternator to B+ pole. Right next to the B+ pole is the connector for these wires.
    Plug wires we labelled here

    http://www.bimmerboard.com/forums/posts/560991/

    and the wiring diagram let's take from a 1989 750iL
    http://shark.armchair.mb.ca/~dave/BMW/e32/e32_89.pdf
    Shogun tricks and tips for the E32 series are HERE!

  2. #2
    Join Date
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    Brantford ON Canada
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    735iL - 1989
    Well, here's what the diagrams say . . .

    M30 and M70 have the same oil level switch, B205.

    Pg 6200-15 shows the YEL wire at the sensor (Static contact) changing to BLU/YEL at connector X1533 and heading to X18 pin 26 of the CCM. This wire will be either short to GND (low oil level) or 1000 ohms to GND (sufficient oil level)

    And the WHT wire at the sensor (Dynamic contact) changing to BLU/WHT at connector X1533 and heading to X19 pin 8 of the CCM. This wire will be either short to GND (sufficient oil level) or open circuit (low oil level).

    As for starting, I think the engine will start even with the CCM removed (when there can be no opinion about oil level) - we see CHECK CONTROL as we drive down the road. So I do not think that a low oil condition will prevent engine starting.

    E&OE.
    Last edited by E32FAN; 04-02-2011 at 06:16 PM.

  3. #3
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    11/88 E32 750iL+98 E36M3
    The reason why I am asking is a question from Rich 1990 750iL: quote

    A good clue on my intermittent no start issue
    I bravely took the car for a 60 mile trip yesterday morning. It started fine and I drove those 60 miles to my destination. Put in a full day's work and 8 hours later started it up to drive back home. As usual that V12 runs like a sewing machine. 2 miles from my house I get off the highway to take a leak at McDonalds. I do my business and sure enough it won't start. I tried it a dozen of so times in P or N, lights on and lights off....nada. I decided to open the hood and look around, I know where the starter is but of course it can't be seen with that V12 in the way, so I pulled my coat sleeve over my hand and whacked the POS battery terminal by the heater valves really hard twice. I got in the car and yoohoo it started. So I think I am finally on the right track as where to look. Other than the wire that runs from that terminal to the alternator (in a tube), what other wires run to that terminal. I am terrible with electronics and I can't read those schematics at the end of the Bentleys.
    unquote
    and that is the reason why I asked for the oil level wire, as that is also going thru the same pipe as the wire from the alternator and ends next to the B+ pile where the connector is.
    http://bmwe32.masscom.net/sean750/sp...ewLeftBank.jpg
    http://bmwe32.masscom.net/sean750/sp...ingScreens.jpg
    exactly that connection in the hand, Johan says: "Remove the starter connector:"

    http://bmwe32.masscom.net/sean750/sp...gConnector.jpg
    http://bmwe32.masscom.net/sean750/sp...orOverview.jpg

    wire colours on that plug you know from my write up to change the alternator cable
    http://twrite.org/shogunnew/fixes/electricalpower.html

    any hints?
    Shogun tricks and tips for the E32 series are HERE!

  4. #4
    Join Date
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    735iL - 1989
    Could this be a bad starter issue - a defective commutator segment?

    The other thing that was happening while the 750iL was stopped and Rich was whacking the POS post with his coat sleeve over his hand - is that his starter motor was cooling down from its peak temperature caused by the hot block and dual exhaust manifolds. Well, the temperature was changing, we can say with confidence.

    That might cause the carbon brush to come into range of a good commutator segment so the starter motor can produce torque.

    Just lifting the hood is the biggest motivator of temperature change.

    I would say that for all "Engine Hot, No-Crank" conditions, the best thing is to open the hood and sit quietly for 15 minutes. Then your car will start smartly. This works for all manner of heat-induced intermittent conditions.

    Just a thought.
    Last edited by E32FAN; 04-02-2011 at 08:05 PM.

  5. #5
    Join Date
    Jun 2010
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    TX
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    My Cars
    1983/84/85 745i

    Thumbs up

    Mine starts when it is low, has many times as I have forgotten to check the level due to my leaking valve cover gaskets.
    I make E23 parts.
    09/1983 745i (stolen spring '13 around Houston, TX Achatgruen on nutria buffalo. 8481080)
    10/1984 745i
    11/1984 745i
    11/1984 735i (10:1-265/6)
    Ford, MB, and GM round out the pack.



  6. #6
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    11/88 E32 750iL+98 E36M3
    Just a follow up to other M70 owners, how is that with your M70?

    Also read here, 2.25 MB tech training instrument cluster and check control
    http://www.e38.org/e32/BMW_pdfs/INST_info.pdf
    display CC
    Priority II:
    engine oil level low - closed circuit to ground via oil level sensor dynamic contact

    oil level sensor - open in dynamic oil level sensor circuit (dynamic contact and 1k OHM resistor)
    Diagram and explanation also on page 19
    Last edited by shogun; 07-02-2015 at 10:06 AM.
    Shogun tricks and tips for the E32 series are HERE!

  7. #7
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    Green Bay, WI
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    1992 750il / 1991 560 SE
    All I can say is the car starts fine without the sensor. I disconnected mine to replace the positive power lead to alternator. I started the M70 several times, even drove it. I got an error specific to the sensor I think. I can check again. I do not recall if the error was just low oil or oil level sensor.
    ______________________________
    1992 750iL

  8. #8
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    On the German E31 forum someone had the problem that the M70 engine oil level warning light did not/never go off. He checked/replaced the connector plug below the lower oil pan, cleaned everything, also replaced the plug next to the B+ pole where the wires come up from below together with the exciter wire from the alternator. He even pulled the wire loom out of the metal pipe which goes along at left side/driver side of the cylinder bank 2 with the fat power cable from the alternator. These wires were also in bad shape due to the heat there, but that also was not the cause of the problem.
    Then he removed the sensor from the lower oil pan and checked it. The float of the sensor is magnetic at its bottom. If this side is too close to the sensor, the message 'Check oil level' is displayed. The switch is installed from below in the small oil pan of the M70 and is thus almost completely in the engine oil. The oil can penetrate through 2 small openings into the housing into the float chamber and lifts the float.
    Over the years deposits are formed on the bottom of the chamber, which on the one hand remain attached to the float and thus give it more weight, and which can also "stick" the float to the ground.
    So it must be cleaned. And after cleaning you must here is click when you tilt the switch in your hand = the float is moving.
    2 possibilities;
    remove it and clean it with some cleaner like brake cleaner, wash in diesel/kerosene oil etc., so that the sludge runs out from the 2 openings of the cover
    disassemble it and clean it
    Disassembling is not that easy done. To open the housing the lid has to be removed from the top. The lid is a thin aluminum sheet metal, this sheet has to be un- bent at the edges. Under the lid you can see a soldering point on a rod, which is the end of the rod where the float moves. The soldering point must be melted and the upper housing part removed from the bottom housing part. Now you have free access to the float and float chamber to clean it. Then re-assemble.
    Problem was solved after cleaning, no more engine oil level warning
    Shogun tricks and tips for the E32 series are HERE!

  9. #9
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    additional info from a tech info with regards to low oil level:
    the oil level sensor has 2 switch contacts
    -static contact
    -dynamic contact
    The static contact is closed when the oil level is sufficient. The dynamic contact is open and the monitoring voltage flows against ground through the 1 K ohm resistor. A defect is reported when the oil level drops below the dynamic switching point. The defect report remains stored in the memory, so that it is not cancelled when the oil level rises after stopping the engine. The defect is report is only cancelled, when the static contact closes.

    Engine oil level is in priority level group 2 . The check control will display priority 2
    text display with ignition ON and OFF
    -20 second display only with car stationary:
    -includes reports concerning actual fluid levels and general information
    -text lights up from ignition lock position 15 and after stopping the car or with the ignition lock in position "0".
    -reports can be called with the CC button within about 2 minutes stopping the car.
    -if several defects occur simultaneously, the one with the greatest importance and the plus sign will be displayed.

    Acoustic indication (gong)
    an acoustical signal (gong) is produced in addition to the text display when an emergency defect is concerned, e.g. defects of priority group 1.
    Priority group 1:
    -includes such defects which could have direct influence on the handling or operating safety of the car
    -the displayed text lights up immediately in case of defect
    -these defects cannot be cancelled with the CC button
    -if several defects are reported simultaneously, only the last defect will be displayed with a + sign
    -a gong will highlight the importance of the defect
    -the other defects can be displayed by pushing the CC button.
    Shogun tricks and tips for the E32 series are HERE!

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