Hi
I recently rescued a 94 945 turbo from the US with 110, 000 miles on the
clock.
When I got the sparkle of my eye home I received a letter from Volvo Canada
stating that there was an outstanding recall on my gem. Gee, 12 year old
recall uh?, seems like a good thing but I am superstitious as we are in the
13th year. So I took it to the local Volvo Dealer and they install a new
Crank Sensor.
Recall #68 Engine Speed Sensor.
What is a Crank Sensor?
What does it do?
Where is it located?
Thanks
In current parlance it is called the crankshaft position sensor (CPS)
alternatively it's been called an engine speed sensor, RPM sensor or
crank trigger.
The outside circumference of the flex plate (holds the starter ring
gear, sandwiched between the transmission torque converter and the rear
end of the crankshaft) is perforated with equidistant square holes save
for the space that would occur at TDC. There are different numbers of
holes depending on whether you have an LH injection system or a Regina-
Rex system. The sensor itself is a simple winding around a permanent
magnet. As each metal bit between the holes passes beneath the sensor it
creates a voltage. When the computer counts to 47 or 43 it expects the
next impulse to be missing and the motor must be at TDC. After one
revolution it can calculate TDC exactly and fire the spark plug plug 10
degrees or more before that. Which plug gets fired is determined by the
position of the distributor rotor. A second consideration is that the
motor is turning and therefore will require fuel, so the fuel injection
control unit triggers the fuel pump(s) relay and allows the engine to
start and run. So if the signal is missing or interupted the car stops
running and will not start.
It is located on the vertical and longitudinal centerlines of the engine
relative to the cylinder bore at the rear of the motor anchored in a
cheesy little aluminum bracket that is bolted to the block and is
positioned in a U shaped cut out in the top of the transmission
bellhousing.
The recall was to replace the early sensor with white tape to the newer
sensor with yellow tape. They all have white tape now P/N 271949 $67.53
Dealer List.
Bob
