1986 900 warm start running rich...

May 02, 2006 6 Replies

I've got an '86 900, 2.0 liter naturally aspirated. When I have a warm start situation (car sitting for a short time, hasn't cooled down fully), it runs very rich when I first start out.



What I'm thinking, is that the cold start injector is opening, as if the car was actually cold, and that there's probably a temperature sensor which is giving the system bad information. Does this make sense? If so, where is that sensor? (This car has CIS injection).



Thanks, Dave Hinz



in article snipped-for-privacy@individual.net, Dave Hinz at snipped-for-privacy@spamcop.net wrote on 02/05/2006 19:17:

The "thermo-time switch"? It's either between cylinders 2&3 in the head, or in the block under the distributor. That instructs the cold start injector to run for a short which during warm up, as well as other parts of the CIS system.

Paul

1989 900 Turbo S
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in article snipped-for-privacy@individual.net, Dave Hinz at snipped-for-privacy@spamcop.net wrote on 02/05/2006 19:17:

I have a year 2000 Bosch K-Jet manual if you're interested (in PDF). I'll drop it in your inbox if so :)

Paul

1989 900 Turbo S
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Ah, ok, I know the switch and have more. I'll take a look for corrosion or loose contacts first, and if that's happy, I'll pull out the meter and look at the switch. Thanks, Paul.

Dave

I've got a Bosch CIS manual available for downloading from the tech library page on my site at "

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". Could well bethe same document you have as the one I've got is PDF as well. But yes the thermo-time switch is the device which controls when the cold-start injector receives power. The t/t switch is actually a double-purpose device since it has a heating element that slowly heats the body of the device at a pre-set rate after 12 volts is first applied to it, plus it absorbs heat from the engine so when the engine is above a certain temp it won't allow the cold-start injector to operate on cranking/starting.

The Bosch t/t switch that Saab used with 8V engines in c900's is the one ending in -217. You can't really use a different one since they're made with quite widely varying settings for cut-off temp and heat-up time, but if you're lucky to find one that's close it'd be ok. I don't know if they all have the same thread size/pitch - maybe the one for the Saab engines isn't interchangable at all.

There are checks to make sure the thermo-time switch and cold-start injector are working properly and they're simple to do with a multi-meter, etc. The bentley manual covers this well on pages 240-10 and 240-11. It's helped me diagnose the fault with the t/t switch on the engine in the turbo car I'm fixing - it's heater resistance was varying massively with any vibration or just a touch of my fingers on the wire harness and it was probably a dud internal electrical connection to the bi-metal strip.

Good luck solving the problem.

Craig.

in article e38v5c$ojj$ snipped-for-privacy@yoda.apana.org.au, Craig's Saab C900 Site at snipped-for-privacy@lios.apana.org.au wrote on 03/05/2006 01:57:

Sorry mate, your site is a little slow. I gave up after a few minutes :)

I have an older one (from around 1974) with a black & white picture as the front page. That file is around 5 Mb. I also have a newer manual from 2000 with a colour picture as the front cover, weighing in at around 1.5 Mb.

Paul

1989 900 Turbo S
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Only got 128 k ISDN here. 8-)

Craig.

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