Crankshaft Position Sensor stuck

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tbear2500
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Joined: Sat May 26, 2018 4:09 pm
Location: Madison, WI

Crankshaft Position Sensor stuck

Post by tbear2500 »

I'm helping my dad with his no-start 1983 633CSi this weekend. At this forum's suggestion, the first thing we checked was the resistance on the crankshaft speed and position sensors. Speed sensor read 995Ω, position sensor 1.35MΩ. None of the local parts stores had one in stock (no surprise there), so we've got to order online.

We spent quite a while trying to get the old one out this afternoon with no success - took off the two bolts that hold on the guard, then took off the two standoffs they were screwed into that hold the sensors in place, but the sensors won't budge. Both of them can rotate but after probably an hour of twisting and pulling they still look like they're flush against the housing. Is there anything else I have to do? Any suggestions for getting them out?

A bit off topic - prior to jacking the front end up, we decided to check for a few other common problems. All the relays tested fine, but the layout of the ones outside the fusebox doesn't look quite like anything I've seen online - my interpretation (given the sizes and colors of wires connected to the relays) is that from left to right they are fuel pump, O2 sensor, and main. Does that look about correct? Can anyone say what the longer silver box (assuming it's another kind of relay) next to the main relay is? It has two sets of parallel connectors perpendicular to one another, like an 'H' with a bar on top.

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Ralph in Socal
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Re: Crankshaft Position Sensor stuck

Post by Ralph in Socal »

Remove the flywheel cover between the trans and motor. You can get access to the tips of the sensors when the cover is removed. Be careful not to deform the tip of the sensor as it will be difficult to pull out. The sensors have a sealing oring that will get stuck in the bore. Spray a little lubricant to wet the orings before trying to remove the sensors.

Search the site for info about the relay. Several threads on it.

Ralph
There is a very fine line between "Hobby" and Mental Illness.

85 635csi Zinno Auto
84 528i Euro
83 635 Euro Arktik
81 528i Kastanien 5-speed
88 528e Bronzit (Granpa Car)
86 535i Auto (For Sale)
81 633 csi (retired)
tbear2500
Posts: 2
Joined: Sat May 26, 2018 4:09 pm
Location: Madison, WI

Re: Crankshaft Position Sensor stuck

Post by tbear2500 »

A bit of WD-40 and some more persuasion got the job done this afternoon. We'll be ordering the replacements momentarily and hopefully putting them in and getting the car started next time I visit. Two questions remains though - the two sensors are the same part, right? Most of the part number got worn off of one by attempting to remove it with a needle-nose vise grips. I believe I read somewhere that they are but I can't find that now. And only one of the bolts/standoffs had washers on it. Is there a reason for that? Is one just missing a washer? Does it matter?

Thanks for the help.
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hornhospital
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Re: Crankshaft Position Sensor stuck

Post by hornhospital »

Yes, the sensors are the same. And the socket head cap screws are each supposed to have a washer. One got lost sometime in the distant past. It's easy to drop one (or the screw and washer, for that matter) while trying to place the screw in the sensor.
Ken Kanne
'84 633CSi "Sylvia"; '85 635CSi "Katja";'85 325e "Hazel Ann"; '95 M3 "Ashlyn"
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