The sensor on the engine lifting bracket

[mxl556]

Hi all,

1981 320i. While working the car last night, I saw that there is a sensor on the engine lifting bracket that is broken. Wires are still connected but the sensor itself fell apart. I found the reference that it is some kind of 17C sensor for the fuel injection enrichment, but don't know what it exactly does. Probably the reason it does not run quite right when it is warm.

Does anyone know what it does exactly? Part number for it? Maybe anyone has a spare working sensor one they are willing to sell?
I need to find the replacement and so far I have had no luck.

I will make and post the photo later today.

Thank you,
Max

[amarino]

This one?
2012-02-11_21-53-24_813.jpg

Looks like its in RealOEM under the Engine > Timing Case > #18 Temperature Switch

https://www.realoem.com/bmw/enUS/sho...48#12631279721

[320iAman]

Amarino has it right ,17C Engine temperature Switch,BMW 12631279721, I ordered one thru BMW Dealership , New ones are in Germany , BMW Group. I got like 3 used ones that work, new one is better, used ones should be considered temporary.
12-63-1-279-721-BOE.jpg12-63-1-279-721-BOE_1.jpg12-63-1-279-721-BOE_2.jpg

Randy

[mxl556]

Yes, this one! Thank you very much!

Never thought it would be under timing case in the parts catalog. I was looking at sensors and cooling system/fuel injection.

Max

[mxl556]

And it's not even that expensive - about 10 times cheaper than the thermotime switch was (paid over $200 for it last year!).

[mxl556]

Here is another question- I am replacing the starter and wondering if I need to replace intake gaskets every time? I had them replaced about 5 years ago when I had the intake off and they look as good as new but oily (blowby). Front gasket is shared with the coolant divider and coolant started dripping when I loosened the nut, I wonder if this one needs replacing. I am tempted to do it right, remove the intake completely and replace all the gaskets, but on the other hand, I do not really want to mess with fragile plastic lines, wiring harness, etc. There is enough room to move the intake out of the way with the lines connected to pull the starter.

Thanks!
Max

[320iAman]

You don't have to take out the intake manifold-disconnect battery cables Negative cable 1st and cables to the starter , take off the bracket in back of the starter and two bell housing securing bolts, then take out the big rubber boot-loosen the big clamp and small clamp, next loosen the bolt under the volume air box which the big end of the rubber boot is attached too by the big clamp and two small nuts that hold the volume air box to the alternator bracket you can then pull the volume air box back slightly to clear the alternator bracket and it will then move forward enough to take out and install the starter, note--- take out the small air boot from the air cleaner box to the side of the volume air box as well and remove the air filter box too before moving the volume air box with the fuel distributor to remove and install the starter.. You can disconnect or loosen the fuel lines to the Fuel distributor if your not comfortable moving the volume air box with them secured in, install is reverse of taking it out battery negative last step.

Its a detailed job takes a few hours.

I have done it several times as above without disconnecting the fuel lines- no problem.

A few inches of clearance is all that is needed.

You can remove the support bar as well to get more room that is attached to intake manifold that has the WOT switches on it, that brown wire with ring terminal on the bottom of the support bar is quite necessary to run the car make sure its attached in when installing the bottom securing bolt, if you remove it to get more room underneath the intake manifold for starter remove and install. This also will require working with the throttle cable , however can leave attached without removing the throttle cable just swing the bar out of the way a little.

Make sure wire No 50 the black ignition wire is plugged into the start solenoid male terminal of the Starter and not the one used for models with points as this connection would go to a power resistor to keep the coil at steady voltage for start up along with the start solenoid male terminal connected. It wont hurt anything the starter will not work though until connected to the start solenoid starter terminal.

Randy

[mxl556]

Thank you Randy.

Blue binder does not say anything about moving things out of the way other than the airbox, maybe original starters were smaller and there was enough space remove them. When I did starter last time ( yes, it did not last as long, maybe 50K miles),I pulled the intake as I wanted to replace all the gaskets, hoses, etc.

This time I do not need to replace anything,so moving AFM aside would do the job. Last night I was wondering if I could move the volume air box, I loosened 2 small nuts on the alternator bracket, but did not find another bolt, so I went ahead and started removing the manifold. I figured, may as well do it the way I did it last time and check things as I suspect that there might be a vacuum leak. Well, gaskets look as good as new, so it was a waste of time I guess. Broken temp sensor is probably what was causing warm running hesitation. Now, since I pulled the intake, I should probably use new gaskets and put it all together.

I guess I will try to move the AFM aside and put the manifold back on. I probably should replace the gaskets as i have them and they apparently need to be replaced every time the manifold is off. What do you think?

Thank you,
Max

[mxl556]

Thank you Randy, that is very helpful. I wish I knew that 3 nuts to move the AFM/fuel distributor is all that is needed

I got the airbox out, support bar out, throttle cable out of the way, WUR out of the way, dipstick support bracket loose.I disconnected all the connectors and wiring is out of the way.
I loosened the intake and pulled it off already too. Now I have room to take the starter out.

I will move the AFM as you suggested and will get the starter replaced today. Then it's a matter of putting it all together, should not be a big deal.


Max

[cgifool]

... should not be a big deal....

Max

lol, famous last words!!

but seriously, sounds like you're well on your way, definitely not the funnest job out there!

[mxl556]

kinda turning into a big deal as I keep finding broken brackets, misrouted harness (i don't think the positive starter wire should go behind the oil filter housing rubbing on the engine block?).

This sensor has to come from Germany, so it would take couple of weeks to get it. Does anyone know how it works? When is it closed/open? I would use a jumper wire (or disconnect it) for now to keep the car running right (i.e. it is always over 17 degrees C).

Thanks!

[320iAman]

The 17C Sensor shuts off enrichment cycling when below 17C above 17C enrichment cycle starts , it connects to the ECU-Lambda Unit and a part of the Cold Start System below 17C , above 17C its part warm running circuit. While its below 17C the lambda unit is in open circuit mode-no enrichment-fuel to Fuel Injectors controlled by the spring pressure , when above 17C the FMV starts working and the lambda unit is in closed circuit mode increases fuel to fuel injectors via O2 sensor , bending of the Fuel Distributor Plate , ect. Enrichment is done in cycles-- for which the FMV is open and close--very fast--and is a pulse train generated by The lambda Control Unit. the buzzing sound is the FMV opening and closing via commands from the ECU-Lambda Unit-the pulse train---very very fast. In NASA-Rocketry terms the FMV is a servo mechanism, it does work via commands received.

Each System has parts that must be good for the Car to run and operate properly, Start System, Fuel System, Charging System and so on.. Your on the right track--make the all the essential parts good.

Randy

[mxl556]

Thank you Randy. Do you know if this sensor is open or closed above 17C? I need to know what it does when the lambda system is in closed loop so I can either use a jumper wire to connect two wires or leave them disconnected to make sure K jet is operating properly when in closed loop. It is warm outside now, so I do not care how it runs below 17C.

Thank you,

Max

[amarino]

From the ETM it looks like its open above 17C
e21-17c-coolant-switch.png

[mxl556]

Thank you!

[320iAman]

lol, Yes,,, below 17C closed circuit, above 17C its an open circuit. Voltage thru the 17C sensor is like a 12 Volt signal ,instruction, command ect to the ECU to not do enrichment cycling under 17 C---this is when the warm up circuit is running after the warm up circuit is done above 17C -12 Volts is absent, enrichment cycle begins via Lambda Circuit or close enough. Putting it another way its a temperature switch that turns off and on the ECU, Speed Relay and WOT switches do the same thing except 3500 RPM's off and Gas Pedal Floored off. The 17C Sensor or Engine Temperature Switch is opened and closed by a bimetalic wire that bends making and breaking contact according to the temperature in Celsius. The voltage across the bi metalic wire has a lot to do with it when breaking contact initially high resistance-high heat emitted -cold motor, after that its the heat of the motor.


o·pen cir·cuit


/ˈōpən ˈsərkət/

noun
noun: open circuit; plural noun: open circuits


an electrical circuit that is not complete.







Randy

[epmedia]

Here's a copy of the '81-83 e21 320i electric manual. Please save a copy

http://findmymerchant.com/images/ele..._1981-1983.pdf

[mxl556]

Thank you!