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built engine wont start cooling fans stay on


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just finished building this motor, car wont start, it sputters like it wants to start while cranking but doesnt come alive, also theres an occasional backfire when i let off the key. another thing it does is the coolant temp gauge reads hot and the fans stay running high, the coolant temp sensor is plugged in. but there is no coolant in the system yet. the accessport reads a temperature of 248F which indicates no coolant temp sensor. there is one last thing. a connector underneath the main engine connector. it has 2 prongs but i couldnt find anything that hooks up to it. any ideas?
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The connector you're referring to sounds like the EGT probe from the stock up pipe. It's fine to have nothing plugged in there - just disable the codes in the ECU.

 

I also think it sounds like someone saw the green connectors in the passenger footwell and said "Hmm, these should be connected", leaving you where you are now. Disconnect them!

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no unfortunately its not the test mode connectors, i had them connected when i was flashing the ecu with my custom map. problem is when their connected the dash reads ERR HC. normal yes, but when i disconnect them, turn the key off and reset the ecu it still reads hot , accessport measures coolant temp at 248* all the time. so far ive tessted the sensor and continuity between the connector and the giant plug for it on the harness. im not sure if this is a common problem or something on my ecu is fried
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ive tried it with the accessport un installed it still does it and i tried it with the sensor unplugged it still reads a constant 248 degrees, on, off , hot cold you name it. im going to hunt down the ecu tomorow and do a voltage drop
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  • 2 weeks later...
I just put an 02 Legacy LEFT (Driver) Cam on an 03 Impreza block with Right Cam. Engine turns but will not start. Checked for spark and no spark. Checked for voltage to primary coil an no voltage. Searched forever for any disconnected wiring harnesses and found none. Checked all fuses and all good. Heard strange noise coming from top of intake manifold. Please help me! I'm out of ideas and running out of time!
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  • 6 months later...
Wondering what solution if any you found for this. I've got the same problem . . . . . New engine, P0117 engine coolant temp voltage low, replaced the sensor still reading 248 degrees. Fans come on high car will not start. Any help would be greatly appreciated.
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check your wiring, mine turned out to be some kind of prolblem with the two wires going to the CTS, i ended up jumping the circuit and running fresh wires from the harness to the sensor. problem solved.
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  • 4 years later...
same issue i have on my 5eat after my re-rebuild, Questions i have is does the cts wire just run directly to the main harness near the turbo?(1) or does to run to the fuse/relay box then the main harness?(2) :spin:
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  • 2 weeks later...

Had this same problem couldn't find solution on the internet. After 2 hours of reading the fsm, testing wires, using jumpers, etc, it came to me. I had the ects connector and fuel purge solenoid connector swapped. Fuel purge is battery voltage and a ground through a solenoid. ects is 5v reference signal and ground. So if you swap them the volt drop across the solenoid isn't much and your ecu thinks its super hot because of low resistance. This pegs your guage, which of course turns on your fan. If the op ran a wire around to the ects from ecu, his purge solenoid probably isnt working now.

 

Sent from my 831C using Tapatalk

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  • 1 year later...
Had this same problem couldn't find solution on the internet. After 2 hours of reading the fsm, testing wires, using jumpers, etc, it came to me. I had the ects connector and fuel purge solenoid connector swapped. Fuel purge is battery voltage and a ground through a solenoid. ects is 5v reference signal and ground. So if you swap them the volt drop across the solenoid isn't much and your ecu thinks its super hot because of low resistance. This pegs your guage, which of course turns on your fan. If the op ran a wire around to the ects from ecu, his purge solenoid probably isnt working now.

 

Sent from my 831C using Tapatalk

I know this is a old thread to bump but I have this same issue maybe the same issue for me but I can't really see how I installed the wire harness and the ECTS wire just "fits" to the sensor the purge solenoid has enough wire length.. I can check tomorrow after work.

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I know this is a old thread to bump but I have this same issue maybe the same issue for me but I can't really see how I installed the wire harness and the ECTS wire just "fits" to the sensor the purge solenoid has enough wire length.. I can check tomorrow after work.
You can check with a multi meter if you want. One has 12v and one has 5v.

 

Sent from my SM-G930P using Tapatalk

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  • 11 months later...

This makes sense. The connectors fit either way. I have been chasing this same problem for a week after pulling manifold and harness to fix some drivability issues on my 08 OBXT. I have actually been stuck on the side of the road this whole time, and living in the freakin car.

 

As it is almost midnight, I will wait till morning to test this and report back.

 

Thanks pazuzu

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This thread to which you're necroposting has at least 3 complainants and plenty of curve balls. Pretty much impossible to tell what your problem is. You will get much better results if you start your own thread with a specific description of your problem.
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