89550-60100 Emission Computer Calibration

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How would the set point get higher than it was supposed to be?
Is that a mistake from factory or is it just the age of the module?
 

Engineer8000

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It was just slightly high out of tolerance, the voltage in this part of the circuit is not regulated. I replaced a diode and capacitor that did get the setpoint down to about 1400 ohms vs 1000 where I found it. There was still very little hysteresis though, maybe 100 ohms or so which is just a few degrees.
 
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Engineer8000

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One other thing to point out is back in the day they used some kind of glue to hold the caps in place during soldering. What they did not expect is it becomes conductive over time and starts making it's own circuit. It should be removed if possible.

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Engineer8000

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This is the third one, it was completely unresponsive. It suffers from a common problem with all these modules, broken solder joints at the connector.


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Wow super informational thread. I have an 81 FJ40 that the carb fan just quit working, Idle solenoid quit some time ago...now wired with direct ground. I'm getting ready to reflow solder on my computer to hopefully fix those issues. As an expert, any advice? Things to look for, potential problems, etc. Thanks in advance.
 

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The carb fan is controlled by its own controller, I think mounted behind the air duct for your truck. The 81+ emission computers are pretty reliable, I would replace the electrolytic caps and reflow the solder for the connector. @ToyotaMatt sells fuel cut solenoids. The fan controllers are another story. If you ground the wire to the temp sensor for the carb fan, and the fan comes on, it tells you the fan controller is probably ok and the sensor is bad. If the FCS is working with a separate ground then the emission computer is likely at fault.

I also have all of the special interlocking connectors for the emission computers.
 
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Wow super informational thread. I have an 81 FJ40 that the carb fan just quit working, Idle solenoid quit some time ago...now wired with direct ground. I'm getting ready to reflow solder on my computer to hopefully fix those issues. As an expert, any advice? Things to look for, potential problems, etc. Thanks in advance.
The carb fan is controlled by its own controller, I think mounted behind the air duct for your truck. The 81+ emission computers are pretty reliable, I would replace the electrolytic caps and reflow the solder for the connector. @ToyotaMatt sells fuel cut solenoids. The fan controllers are another story.


it's important if you have a 2 wire Fuel Cut SOLONOID you stay a 2 wire , if you only have a single wire type ?

my kit addresses this issue with the supplied 2 wire green 2 wire harness side connector witch are both water proof when latched together properly

LINK to more info here :




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FCS has been working fine for several years with direct ground...so I guess it could be computer solder? From what I understand it cracks at connector. Checked engine fuse but still need to check 5A inline fuse for carb fan. Thanks again I'll let you know.
 
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Ok more confused than ever. Fan runs normally jumped to ground. I've read all the threads on carb fan, but still have questions. First of all I have 1981 40. I checked inline fuse and seems intact. It actually has a 15A fuse which corresponds to wiring diagram...guess it's different than 5A I've read about in other posts. Didn't check it with meter but looks OK. Anyway, questions. Does fan have input from emissions computer? Would reflowing that help or is it only controlled by cooler fan controller? What actually is controlled by emissions "computer"? WHat's the check for temp sensor? What if I grounded it directly would the fan still run on timer? Probably basic questions but I'm certainly no expert. I bypassed FCS by grounding and wiring it to switched power..works fine. Thanks in advance for the help/info.
 

Engineer8000

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When you say, jumped to ground, I assume you are grounding the lead that would normally connect to the temperature sensor? If you ground that lead, after shutting off the engine, the fan should run for around 30 minutes and shut off. The fan controller will think the carb is hot and run untill the timer times out.

The temp sensor is NTC so the resistance decreases with temperature increase. Depending how hot it is, it could read 1kohm or less. If it is higher than say 4.5kohm when hot, it is not working.

The fan is not connected to the emission computer, just the fan controller. The '81 emission computer controls VSVs for EGR and air injection, and the fuel cut solenoid, based on inputs from vehicle speed, rpm, catalytic converter temp, and manifold vacuum switch. The emission computer had different functions over the different model years.

Those glass cartridge fuses can look perfectly fine and be open.
 
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Hey thanks. Yep I grounded temp sensor wire after cycling key on and off...fan came on. Does that mean the controller is working and issue is with the sensor? Was thinking the same thing about the fuse. The only reason I didn't change it out is it is not actually easy to get to with two hands to remove from connector without pulling on wires...but I will now just to make sure. It looks like the original one. Also got the multi-meter out to test it on truck, but same thing couldn't get it on both ends. BTW, does the temp sensor need to be removed to test? Do I just test resistance between connector and body of sensor? Thanks for the info...as you can tell I'm a novice. Although I have managed to keep the 40 running for 40+ years.
 

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I'm not sure what that fuse is for but I would guess that if the fan runs at all then the fuse is probably ok. Test between the sensor connector and ground. It does not need to be removed, just unplugged from the fan controller. It provides a variable resistance to ground for the fan controller.
 
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Thanks...I'll let you know. Worse comes to worse I'll just ground it and let it run everytime. But I enjoy learning more and doing stuff myself if I can. I truly appreciate the insights of experts such as yourself.
 
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Just an update. Fan started working fine again. I guess in the process of troubleshooting I must have bumped something that was loose. Checked the wire from manifold temp sensor...it looked OK but I did move it around some. Checked the inline 15A fuse...didn't even take it out, but I did move wire around. Also checked connectors on emissions computer and fan controller...OK. So I'm guessing wire loose/grounded or in the process of moving connectors around solder joint got bumped and made connection. At any rate, I will leave it alone for now and worry about it if it stops working. I'm much better educated on how it works now thanks to Mud.
 

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