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Re: Plug fouling (cold start flooding?) Posted by Dana [Email]  (#2822) [Profile/Gallery]
(more from Dana) on Thu, 5 Dec 2002 21:02:31
In Reply to: Plug fouling (cold start flooding?), RobW, Thu, 5 Dec 2002 17:11:03 Members do not see ads below this line. - Help Keep This Site Online - Signup |
Rob,
I own a 900 8v CIS since it was new. A couple of things happen during the cold start.
1. The pulse modulating valve is locked at 60% until the O2 sensor has had a chance to warm up....at which time the control unit releases the 60% lock and turns over control to the O2 sensor.
2. The warm up regulator drops the control pressure line to approx 35 PSIG to enrich the fuel mixture with the fixed 60% modulating valve. As the warm up regulator warms up due to engine heat or its internal electric heater, the control line pressure will slowly increase to approx 55 psig for your car.
3. The auxillary air bypass valve is cracked open to increase the engine
rpm up to about 1100 for a couple of minutes while it is warming. Its internal electric heater or the engine temperature will cause the auxillary bypass valve to close. The valve is a calibrated bypass air flow around the throttle plate.
4. The cold start injector is activated during cranking for a maximum of 7 seconds (?) depending upon how cold it is. The lower the temperature the longer this function is on. But this should stop if the thermo-time delay switch located between cylinder 2 and 3 opens to disconnect the injector power lead connection to the car body. Two things cause the switch to open and deactive the injector. Engine water temperature at 115F or an internal electrical heater which warms the sensor during cranking. In practice, however, the electrical heater will deactivate the switch in just a few seconds. This switch is a real possibility for your problem but you can test it with an ohm meter. It has two electrical pins on its top. The heater resistance between the two should be 40 ohms. One of the two pins to the engine block will be shorted by a temperature switch which opens above 115F. There is a 40 ohm heater connected across this temperature switch so the ohm reading will change from a short to 40 ohms.
This "thermo-time switch" is not the only temperature switch which deactives the injector. A second normally closed temperature switch set to open above 77F is located under the water t-stat and is wired in series with the thermo-time switch. But this can not do the things you are seeing. I would focus on the thermo-time switch.
3. If the thermo time switch is found to be ok, I would then look to vacuum switch located under the fuel filter. During the first few minutes of operation this switch can close during cold engine acceleration (manifold pressure) to activate the cold injector to give the engine extra fuel mixture during the the warm up period. I would check to see if it is always shorted.
4. Also the cold start injector could be leaking at all times. You can lift it out and put it into a bucket....activate the fuel pump...look for leak...Same goes for the normal mechanical injectors but you have to lift the air flow plate to get them to spray with the pump on....
To help you identify these items look at my web site page for the 85 SAAB. Button on the link below. I have specific wiring diagrams for the system if you need.
posted by 172.133.19...
, Thu, 5 Dec 2002 21:02:31 <-- Viewing This Message
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