Engine - Cold Start Problems at Low Temperatures
84porsche02Subject Flywheel Reference Mark Pin for DME Sensor
Part Identifier N/A
Applies To 944
1983 only
Group
28
Key Points
Modification to improve cold start at low temperatures
C
Number
84-01
March 14,1984
Low temperatures may weaken the magnetic field between reference mark pin (Part no. 477.105.276.) in flywheel and reference mark sensor, on engines produced before:
Engine no. 43DC392 (with manual transmission) 43DG050 (with automatic transmission)
If engine does not start at temperatures approximately 0~C (32~F) or colder, the following should be performed
Test Procedure
The preferred method of testing the reference mark sensor is with an engine oscilloscope. (See the oscilloscope manufacturers operating instructions to determine correct control positions and tester connections for special tests.)
-connect positive (+) tester lead to terminal 25 and negative (-) tester lead to terminal 26 of the disconnected control unit plug.
-operate starter. Screen should display a single harmonic oscillation. It is important that oscillation begins with a positive flank.
^ Screen scale must show more than 2 volts with starter speed at least 200 RPM.
If voltage is only 2 volts or lower, proceed as follows:
- check distahce between reference mark pin and reference mark sensor. Adjust if necessary.
^ Distance = 0.8 mm +/- 0.05
If distance is correct and voltage still too low, flywheel has to be modified as follows:
Note
A special nut, P/N 944 102 921 01 is required. A regular nut must not be used.
- disconnect battery
- remove reference and speed sensor cables.
- move heater lever to the center so heater valve can be moved for better access to reference mark bore.
- remove reference mark sensor.
- turn engine until reference mark is in center of bore.
- put Loctite 270 (R) (or equivalent) into threads of nut Install nut on threaded reference mark pin using 1/4" socket. (Put some putty in socket so nut will not fall out.) Run nut all the way on.
- re-install sensor and all cables, - lift vehicle and remove protective pan and bell housing cover so that flywheel and reference mark pin are visible.
- turn engine until reference mark pin is in center of rectangular opening of bell housing (in front at bottom).
- drill balancing bore with 6 mm drill bit as indicated. (See above illustration).
^ Manual transmission 4.5 + 0.5 mm deep
^ Automatic transmission = Drill through plate
^ Center of bore to crankshaft side face of flywheel:
Distance = 5.5 mm
Note
Correct depth and location of hole is critical.
-remove all metal shavings from bell housing using magnet or shop vacuum.
- re-install bell housing cover and protective pan.
-re-connect battery.