Cold Start Diagnosis For 1984-85 900, 900S; 1984 Turbo
Model Years: 1984-85 900, 900S; 1984 TurboSymptoms: Extreme difficulty in starting a cold engine when overnight temperatures have not gone below freezing; stalls repeatedly after start up.
Diagnostic and Repair Details
1. Check the following C.I. components which, if out of specification or adjustment, can cause difficulty in starting and driving. The engine must be cold (overnight cold soak outside if possible) before making these tests.
- Check the rest position of the air flow sensor plate with the ignition switched off. The upper edge of the sensor plate should be level with the bottom edge of the air venturi. This is the highest permissible position for the sensor plate. A position slightly below the lower edge of the venturi (0.020", 5 mm) is permissible (see drawing).
*See Warranty Info.
The measurements should be taken from the middle of the lever. The rest position can be adjusted by bending the clip (A, see drawing) for the spring loaded arm on the underside of the air flow sensor. The air flow sensor must first be removed.
- Verify that there is no air leakage between the air flow sensor and the engine.
- Check that the auxiliary air valve is open when the engine is cold.
2. Install Saab C.I.S. pressure test equipment (P/N 83-92-516).
- Measure and note ambient temperature.
- Remove fuel pump relay, unplug wire connector at control pressure regulator (warm-up regulator) and unplug wire connector at the auxiliary air valve.
- Connect a jumper wire from terminal
30 and 87 of the fuel pump relay socket.
Measure the line pressure. Adjust if out of specification.*
Line Pressure Checking Value, 1984-85 4.7-5.4 bar
Line Pressure Setting Value, 1984-85 4.9-5.2 bar
- Measure the cold control pressure.
Compare your readings with the chart at the right. If not within specification, replace the control pressure regulator. (A more detailed graph chart is attached to this S.I.)*
Control Pressure Regulator P/N 75-15-554
3. Test the temperature setting of the thermal switch (located in the front of the thermostat housing).
Remove the thermal switch from the housing. The switch must be tested in a glass of water to meet the following specification.
Thermal Switch Switch Closes at 66~F +/- 5~ (19~C +/- 3~) Switch Opens at 77~F +/- 5~ (25~C +/- 3~)
Mix warm and cold water to achieve a temperature of 66~ F +/- 5~). (Measure with thermometer.)
Connect a continuity tester to the terminals of the switch and submerge the switch in water. Allow the switch to stablize with the water for 1 minute.
If the switch contacts do not close, replace the switch.*
Thermal Switch P/N 75-06-322 (M84-85)
4. Check the cold start injector ground circuit.
Connect a test light between 12v and the (green and white M84/green and green M85) wires on the back of the cold start injector plug. If the ground circuit - is complete and the coolant temperature is below 66~F +/- 5~, the test light will light.
If above 77~F +/- 5~, connect a jumper wire between the two wires at the thermal switch to simulate a cold engine. The ground circuit should now be complete provided the coolant temperature is still below 113~ F. (Thermo-time switch at intake manifold.)
5. Verify proper operation of the thermo-time switch by connecting a test light between 12v and the green wire on the thermo-time switch plug. If the coolant temperature is below 113~ F/45~C, the test light should be brightly lit. Engage the starter for a short period, the light should go out after a few seconds of cranking, indicating the small heating element in the thermo-time switch has opened the ground circuit. Low wattage test lights will glow dimly after the ground circuit contacts have opened. Don't confuse this with a full intensity closed circuit reading.
Connect the test light from ground to the brown wire on the cold start injector. You should have power whenever the starter motor is engaged.
*See Warranty Info.
6. Check the cold start function.
- Plug in the fuel pump relay and re-connect the wires at the control pressure regulator and auxiliary air valve.
Verify cold start injector function by removing the injector and checking the spray pattern. Observe the following steps:
a. If practical, move the car outside, away from sparks and flame and have a fire extinguisher handy. YOU ARE DEALING WITH AN EXTREMELY EXPLOSIVE MIXTURE!
b. Disable the ignition by disconnecting the primary harness plug from the base of the distributor.
c. Remove the cold start injector from the intake manifold, aim it into a container and crank the engine over for a few seconds. With a cold engine (below 113~ F) the injector should spray a finely atomized mist of fuel and close without leakage as soon as you stop cranking. Replace the injector if necessary.*
If the engine temperature is above 77~ F +/- 5~ you must connect a jumper wire between the two wires at the thermal switch.
7. Connect a Saab Pulse Relation Meter (P/N 83-93-597).
Place a jumper wire between the two large pins (3 & 4) of the ignition lock relay socket, position E of the main fuse panel.
This provides power for the meter to function. This circuit is otherwise dead during cranking.
Engage the starter and watch the Pulse Meter. The pulse ratio should lock on 92% +/- 10% during cranking and for three seconds after the engine starts.
*See Warranty Info.
If inoperative, check the transient enrichment relay socket as follows (located in the Emissions Relay Panel):
- Test light connected to 12 volts
Pin 31 - ground at all times
TRK - ground with closed throttle (man. trans. only)
- Test light connected to ground
Pin 50 - 12v during cranking
TIP - 12v pulse on acceleration
87 - 12v when engine is running
11 - pulse ratio of 92% +/- 10% when the pin is grounded
- Ohmmeter or other continuity tester
Pin X2 - continuity with X2 of the decel relay
TKK - continuity with the white wire on the thermal switch at the thermostat housing