Reference Sensor Question
10-14-2009, 10:29 PM
#1
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Reference Sensor Question
So Guys,
Today almost caused me to beat my porsche with the torque wrench....as I saw that it was my fault.
I was attempting to gap the reference sensors with directions from clarks garage. Apparently there is a typo on that site. It says to gap the sensor to the FLYWHEEL with a .8 mm gap...Which I did with the pressure plate off.
APPARENTLY the sensor closest to the firewall is supposed to be gapped to .8 mm above the PRESSURE PLATE.
When I torqued the pressure plate bolts the second sensor (closest to the firewall) must have been touching the starter ring because when the pressure plate turned as I was torquing the bolts, the sensor got caught in it and bent and dented.
I still tried to gap This sensor, but it was dented and bent in the bracket.
I tried to start the car and got nothing. It just turns over and never starts.
Could a BENT or DENTED reference sensor be the cause of the no start?
I don't know how those things work...
Today almost caused me to beat my porsche with the torque wrench....as I saw that it was my fault.
I was attempting to gap the reference sensors with directions from clarks garage. Apparently there is a typo on that site. It says to gap the sensor to the FLYWHEEL with a .8 mm gap...Which I did with the pressure plate off.
APPARENTLY the sensor closest to the firewall is supposed to be gapped to .8 mm above the PRESSURE PLATE.
When I torqued the pressure plate bolts the second sensor (closest to the firewall) must have been touching the starter ring because when the pressure plate turned as I was torquing the bolts, the sensor got caught in it and bent and dented.
I still tried to gap This sensor, but it was dented and bent in the bracket.
I tried to start the car and got nothing. It just turns over and never starts.
Could a BENT or DENTED reference sensor be the cause of the no start?
I don't know how those things work...
10-14-2009, 10:49 PM
#2
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You'll need to replace the sensor. If it's bent and dented, it won't want to come back out of it's hole; you'll likely totally destroy it in the process.
The sensors are just a fine coil of wire around a ferrite magnet core. As something iron (teeth on the flywheel or the grub screw) pass by within a fraction of a millimeter, a tiny electric pulse is generated. To get a strong enough pulse for the DME to read, you need a lot of loops of wire. To get a lot of loops into a small space, you need to use very fine wire. Very fine wire won't put up with much trauma.
There's an equivalent BMW sensor for around $60 vs the Porsche part number for double that.
The sensors are just a fine coil of wire around a ferrite magnet core. As something iron (teeth on the flywheel or the grub screw) pass by within a fraction of a millimeter, a tiny electric pulse is generated. To get a strong enough pulse for the DME to read, you need a lot of loops of wire. To get a lot of loops into a small space, you need to use very fine wire. Very fine wire won't put up with much trauma.
There's an equivalent BMW sensor for around $60 vs the Porsche part number for double that.
10-14-2009, 11:04 PM
#3
Rennlist Member
The Speed Sensor does indeed count starter ring gear teeth.
You'll have to remove the ref. sensor bracket to get it out, unless you want to pull your clutch apart (believe me, NOT).
You don't note what year/model your car is, but this job won't be a treat on any of them.
You'll have to remove the ref. sensor bracket to get it out, unless you want to pull your clutch apart (believe me, NOT).
You don't note what year/model your car is, but this job won't be a treat on any of them.
10-14-2009, 11:18 PM
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The Speed Sensor does indeed count starter ring gear teeth.
You'll have to remove the ref. sensor bracket to get it out, unless you want to pull your clutch apart (believe me, NOT).
You don't note what year/model your car is, but this job won't be a treat on any of them.
You'll have to remove the ref. sensor bracket to get it out, unless you want to pull your clutch apart (believe me, NOT).
You don't note what year/model your car is, but this job won't be a treat on any of them.
I tried starting the car once I installed the slave cylinder and starter because I knew I had dented that sensor and wanted to see if it would start.
Of course it didn't. I tried switching the wires underneath the hood just in case they got switched around at some point but when I tried to detach one of the sensors (the one I didn't have to replace the first time) the end broke off...
So Now I am going to replace BOTH...and hopefully gap the RIGHT one this time. What does that OTHER sensor do? It seems when the reference sensor is gapped correctly to the pressure plate, the sensor furthest from the firewall sits a little higher off of the flywheel.
BUT, once I replace these sesnors, this thing BETTER start...lol. Then I just have to bolt on the TT, put the tranny back in and put the exhaust back.
Thanks for the help,
Matt
10-15-2009, 12:15 AM
#7
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The reference sensor (the forward one) produces a signal at TDC via a set screw in the flywheel, the rear one senses RPM by producing a signal off the teeth of the starter ring gear.
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10-15-2009, 12:21 AM
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oh. SO when I gap the NEW sensors I should gap the rearmost sensor to the pressure plate and that should give about the same clearance between the forward most sensor and the screw in the flywheel?
