Speed and Reference Sensors

[rporzio]

Can someone explain to me what the Speed and Reference Sensors (84 944) do? Are they the same and any other info you can tell me about will be helpful. Thanks, Ralph

[Rasta Monsta]

Speed and Reference Sensors - Checking, Replacement, and Adjustment

[rporzio]

Thanks Rasta, I did see that info on Clark's site, but what I was really looking for is an explanation of what the sensors actually do.

I'll use Clark's directions and tips if I have to replace or test mine.

[KrazyKarl]

One sensor reads a reference stud in the flywheel, and the other reads the teeth on the starter gear I believe. They have magnets on the end that read the metal and send an electrical signal to the DME.

[rporzio]

ok, that's good. What in the world would they have to do with the car suddenly shutting off and then failing to start until hours later when the block has cooled down. These are things that make me go: hmmmm...!

[Rasta Monsta]

Yes, they tell the computer the position of the crank, so it can fire the injectors and spark plugs. If the computer gets no signal from the sensors, it kills the fuel pump (something about burning to death in a 100 PSI gasoline fire).

[rporzio]

Are both of the sensors the same, with the exception of the labels? Thanks, Ralph

[Techno Duck]

Yes, sensors are the same part.

[John_AZ]

Ralph,
If you need new reference sensors, there are interchanges for about $70 each. Stay with the sensors that have the silver case on the bottom portion of the sensor. I have seen some aftermarket sensors with a full plastic case.

Techno Duck and a recent TSB I found, said that the turbo starter replacement (now standard) can cause electrical interference with the sensors and cause hard starts.

What do they do? From an internet parts house.



GL
John_AZ

[SolReaver]

Don't overlook the connectors that go to the sensors, they get brittle and fail with age. A bad connector can present a a bad sensor as the brain can't tell the difference. Cleaning and securing the little pins might do the trick and so IMHO it is worth the 10 mins it will take just to check it out.

[Rasta Monsta]

I read someplace those connectors were made from a special material called Brittelsheiß.

[thekidd]

Originally Posted by John_AZ

Ralph,
If you need new reference sensors, there are interchanges for about $70 each. Stay with the sensors that have the silver case on the bottom portion of the sensor.

Zygmunt Motors: BimmerParts.com has the sensors for $106.56, or abouts, total for 2 sensors. Look at the part number, F6010- 12760, if you change the 0 at the end to a 1, the 1 part number is for the 944's- $100 more for just one! I bought the sensor for a 1979? 320i? series I think, part# is correct so just use that.