LG5 Corsica hatch, coolant switch conundrum??

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ab8127542
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LG5 Corsica hatch, coolant switch conundrum??

Postby ab8127542 » Mon Sep 10, 2018 12:27 pm

bought this car with the 2.8 3spd, block got so hot it split between two cylinders, pulled the heads and tossed the block (except for misc. external parts) I have a few donors and did the LG5 5spd swap, but used the same harness for the most part. Custom tune, 42lb injectors.

Anyway I run it at 160°, and once we were up and going it became clear why the 2.8 over heated, the fan refused to kick on. I had already put a brand new switch in below the thermo housing, before putting the new block in, fan still dead.

okay I went into wiring with my ohm meter. Beautiful ground, clear and concise according to the meter. went all the way into the ecu checking to make sure the switch had a clear path to the ECM. it did, I moved on. My guage works fine, it the temp sensor works. according to my datalog acquisition, the ECM again, sees the correct engine temp, but the SWITCH, reads -38 on the laptop.

But I changed the switch twice now, checked the wiring to no prevail! Still -38. Pulled my prom and told the ECM to leave the fan on at -38 so I can drive it without overheating, but as you can imagine it WAY over fuels, incredibly rich. Like 9 MPGs lol and I don't move it much to avoid engine anguish, I've spent to much on the motor.

Is it possible, the ECU itself has an internal short or disconnect? The wiring to the ECU is fine. I don't ask many questions but I'm pulling my hair out over this one.

-38 no matter what I change. Is this a problem? My donor is a Beretta 5spd a TGP and a few corsicas. I have parts.
thanks..



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ifixalot
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Re: LG5 Corsica hatch, coolant switch conundrum??

Postby ifixalot » Mon Sep 10, 2018 3:19 pm

I do not know the answer for your car as to what if anything is wrong.
But my with 94 mini van, as I recall, I don't think the fan would work because the AC did not have a charge.
Also when I did get it to work after fixing the AC, I was not comfortable with the high temperature before it came on,
it was too hot IMHO.
When I read codes on OBDI, the fan runs when I turn on the key with the diagnostic terminals connected. Maybe yours should do the same?
My solution to have the fan turn on sooner was to get one of these and wire it in, (link). Then no matter what, if the radiator gets too hot,
it will kick on. BTW, if you are driving over 35 mph, the fan isn't really needed. So is your engine getting too hot at that speed?
Maybe something else is wrong.
https://www.ebay.com/itm/Engine-Cooling ... cO&vxp=mtr



ab8127542
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Joined: Sun Oct 09, 2016 1:55 pm

Re: LG5 Corsica hatch, coolant switch conundrum??

Postby ab8127542 » Tue Sep 11, 2018 2:39 pm

my fan kicks on when in diagnostic mode. And I can force it on electronically as I mentioned. I suppose my best inquiry would be into the internals of the 7730 ECM. possibly resistor shorts anyone's come across or internal connectivity issues. I've discounted my prom as an issue since, it's been replaced with one I had installed a flashable chip into out of another Corsica.

It's a problem that's followed two proms two motors and two tunes. I feel like I'm running in circles. The only thing I haven't swapped is the ecm but it seems like such a farfetched probability to me.



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Rettax3
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Re: LG5 Corsica hatch, coolant switch conundrum??

Postby Rettax3 » Thu Sep 13, 2018 6:54 pm

ab8127542 wrote:my fan kicks on when in diagnostic mode. And I can force it on electronically as I mentioned. I suppose my best inquiry would be into the internals of the 7730 ECM. possibly resistor shorts anyone's come across or internal connectivity issues. I've discounted my prom as an issue since, it's been replaced with one I had installed a flashable chip into out of another Corsica.

It's a problem that's followed two proms two motors and two tunes. I feel like I'm running in circles. The only thing I haven't swapped is the ecm but it seems like such a farfetched probability to me.

1. Your car sounds awesome -a 5-speed turbo hatchback Corsy? Heck yeah! Pics would be great.
2. If your ECM can actuate the fan while jumpered into diagnostic mode, it can actuate it, period. Nothing wrong with the power-supply, relay, wiring, or fan.
3. -40 is an open circuit, so I would say -38 is an ALMOST open circuit -maybe just enough connection to get an Ohm-meter signal through, but not enough for the 5v sensor reference to provide an accurate reading -I would be looking at wiring or connectors there. Try jumping the two sensor leads together, watch the ECM read then.
4. I hate to say it, because back in the day, every time something went wrong with one of these cars, the first thing people screamed was 'bad ECM', and it never was. However, the one-chance-in-a-million ECM failure is now one in a thousand, heading towards one in a hundred -everything fails eventually, these ECMs are starting to show their lifespan. So, it could be something wrong there.
5. Try installing a stock ECM and PROM without starting (obviously with 42 lbs injectors, it isn't going to run right, if at all, stock). What is your sensor-read with that?


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1990 Turbo 3.4 5-Speed T-Type
1990 4.0L 4-Cam 32-Valve V-8 5-Speed Indy GTi (Project)
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