Help with sensors 1987 900 T 8v [Archive] - SaabCentral Forums

: Help with sensors 1987 900 T 8v

4th June 2002, 06:19 PM
1987 900 T 8v K-Jetronic (no Lambda)
Please can you help to identify components of my ignition and K-Jetronic fuel system which has an intermittent fault. It wonít cold start, I can almost drain the battery trying, but if I then wait for 2 minutes it fires up fine.
1)Where is the ďThermostatic Time SwitchĒ located ?
2)There are 2 sensors under the thermostat housing, one has a single white wire and the other has 2 wires ( Yellow & Green )What are they called?
3)Between the inlet ports 2&3 there is the Knock Sensor (I think) and the other one has 2 vacuum lines, one goes to the throttle housing and the second to a device that looks like a vacuum switch attached to the other end of the Knock Sensor slung underneath the throttle housing.
4)Lastly thereís a sensor on the block some 6Ē below the Knock Sensor
Whilst struggling through the poor wiring diagram that Haynes provide, I see thereís a Coolant Temp Switch that controls a buzzer which I assume must be behind the dash. One of the above sensors probably does this job.
Thanks in advance for any help received.

<font size=-1>[ This Message was edited by: Dekker on Jun 4, 2002 11:28pm ]</font>

5th June 2002, 04:27 PM
Have a ook at this site, it's an American Saab with AC but shows all the bits you mention...

There is no buzzer on the car, so not certain what you mean?

The knock sensor is bolted to the head under the inlet manifold, you have to pull back the water hoses to get to it!! So maybe your looking at something else!!

There's a good desciption/diagnosis in the Bentley workshop manual!!

5th June 2002, 07:22 PM
Thanks for the reply john-w, the site is pretty good with great photos.
The thing I thought was the Knock Sensor is part of the EGR 2 port system, so this disposes of item (3).
Items (2) is the Temp sender for the dash (single white wire); and the Temp Switch which is part of the Cold Start Injector control.
Item (4) must be the Knock Sensor.
The place where the american car has the Thermo Time Switch is the place where I have EGR inlet connection.
Anyone any ideas on other locations of Thermo Time Switches ?

6th June 2002, 04:29 PM
Thermo time switch is on the front of the engine just below the thermostat housing.

To test; measure resistance between pin 1 &amp; earth.
below 100f 38c 5 ohms or less
above 110f 44c 140 ohms approx

6th June 2002, 04:41 PM
The thermo switch for the cold start injector quite often fails (and isn't really needed anyway unless temps are below -10įc) firing the injector when it isn't required.

It might be worth unplugging the cold start injector and see what happens, pull the plug off the injector.

7th June 2002, 04:41 PM
Thanks for the replies and advice.

Yes I misread the circuit diagram and the part I was looking for was right under my nose, isnít it always the case :smile:

Iíve only been able to measure the resistance whilst hot at the moment but which pin is No.1 Iíve no idea as my wiring diagram doesnít say and craning my neck I failed to see any markings on the plug.

The cold start injector does function OK, tested by applying 12v to it, and it isnít operating when I tried to start motor because I pulled it to see.
So I reckon Iím on the right track.

Previously my motor would fire up very easily so tomorrow after measuring it cold, Iíll try to earth the thermo switch and see if she starts.

The Coolant Temp Switch (122) and Coolant Buzzer (132) are on page 12-18 of Haynes manual diag, no idea if itís a special feature or country dependant. I thought if it was there but not working it would be useful to fix.
Is the Bentley book much better than the Haynes?

1987 900T 8v 5d Burgundy

<font size=-1>[ This Message was edited by: Dekker on Jun 7, 2002 9:44pm ]</font>

9th June 2002, 09:34 AM
No 12v from starter motor solenoid.
Rigged up a connection from terminal 50 through a couple of diodes just incase that another 12v supply swithes in from a time relay. I think that circuit doesn't exist on my machine though as I've no lambda.

Thanks for all the help. Great site.