Cold start injector system question.
05-29-2003, 08:21 PM
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Car: 1986 W69 Special Edition
Engine: 2.8/ECM/Int/Exh
Transmission: T5
Axle/Gears: 3.42 posi
Cold start injector system question.
Hi. Does anyone know at what temperature the cold start injector system sensor changes state? Is the sensor a thermistor, or a dry contact type? Thanks! 
05-29-2003, 09:18 PM
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Car: 1986 Firebird
Engine: 2.8 V6
Transmission: 700R4
LOL, you're really into the cold start injector system, eh? 
It's neither a thermistor or a "dry contact" sensor- it's not even a sensor. It's a switch. Looked up the temp for you (from the GM Service Manual, http://www.helminc.com , hint hint), any time the coolant temp is below 95 degrees Fahrenheight (39 deg Celsius), the cold start switch is on.
Interesting- the book says that the cold start switch actually heats itself... says the bimetal gets heated by the windings in the switch, and will stay "on" 8 seconds at 20 degrees celsius (didn't give fahrenheit and I don't feel like converting) or below.
I guess that means max time for the CSI "on" is 8 seconds?
It's neither a thermistor or a "dry contact" sensor- it's not even a sensor. It's a switch. Looked up the temp for you (from the GM Service Manual, http://www.helminc.com , hint hint), any time the coolant temp is below 95 degrees Fahrenheight (39 deg Celsius), the cold start switch is on.
Interesting- the book says that the cold start switch actually heats itself... says the bimetal gets heated by the windings in the switch, and will stay "on" 8 seconds at 20 degrees celsius (didn't give fahrenheit and I don't feel like converting) or below.
I guess that means max time for the CSI "on" is 8 seconds?
05-29-2003, 10:18 PM
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Car: 1986 W69 Special Edition
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LOL, you're really into the cold start injector system, eh?
The 8-second thing is a bit strange... I can tell when the injector is on/open just by the sound of the engine while accelerating cold. The butt-dyno reports this as well. I'm pretty sure the injector is operating for more than 8 seconds after startup...
It appears to be only a 2-wire device, so the heating thing has me perplexed... Unless it is similar to the flasher module? I'll have to take a closer look at it after it stops raining and I can go out and play.
I'm thinking of a shifter-mounted "fuel performance" button. I should be able to get an aftermarket manual transmission **** with an accessory button. Or, I could just tie it into a TPS monitoring circuit, and open the injector around 85% to 90% throttle...
Does the manual state anything about the injector being PWM, or is it simply open/closed? I don't want to burn the coil out by driving it with 100% duty cycle...
I wonder if it opens at 100% duty cycle at 68°F for 8 seconds and then between that an 95°F it runs at 50% or something similar...
05-30-2003, 09:58 AM
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Car: 1986 Firebird
Engine: 2.8 V6
Transmission: 700R4
The injector's either on or off, there's no in between.
You know a car gets more power when it runs lean, right?
You know a car gets more power when it runs lean, right?
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