I own a 3.1 firebird.

I FINALLY got the cooling system working nicely with a new water pump, now to direct attention to the rad fan which still is inoperable.

As far as the fan goes I have tested its function using the diagnostic ports. With the diagnostic port jumped the fan kicks on and runs fine. During normal operation the fan will not kick on at all, even with temps exceeding 220.

I have replaced the relay up by the drivers side firewall, the coolant temp sensor with the multiple wire plug.

What im wondering is if the other temp sensor (with the single wire lead) has any input into the ecu or does it just run the gauge?

If it doesn't have anything to do with the fan operation would an a/c delete cause any problems with fan operation?

 

On a '91 an A/C delete usually causes the fan to run all of the time. This is because the high pressure switch on the A/C line tells the ECM to turn on the fan. When unplugged, it is always telling the ECM that there is high A/C pressure and the fan needs to be run.

Now, the fan is ECM controlled. There isn't a head temperature fan switch as other f-bodys have.

The CTS sensor is used by the ECM to turn on the fan at the appropriate temperature. Which is north of 228 F.

By shorting A&B on the ALDL and having the fan run (key-on, engine-off), that means that everything from the ECM out is OK.

Which brings us back to the CTS. It may not be reporting the proper engine temperature. Or, your gauge temperature is way off. That uses a different sensor.

RBob.

 

Hmm, Im fairly positive that the temp is reading correctly on the one wire lead sensor. My engine hovers around 160-180, the thermostat opens and it goes down a little lower than 160 then steadily hikes its way up to 220+ I have yet to see the fan kick on at all since i bought the car other than aldl short.

The A/c was removed by the previous owner. Now if the ecm isn't running the fan all the time either the ecm isn't working correctly or something else funky is going on.

My injectors seem to run rish or lean at random and misfire although the timing on it is spot on. Would it be a good idea to pull an ecm from a scrap car and see if it makes a difference?

 

See if you can find the A/C pressure switch connector or wire. The previous owner may have grounded it when he did the A/C delete, which is correct. Or just jumpered the terminals in the connector, which also grounds the wire.

If so then un-ground the wire and see if the fan kicks on. The engine needs to be running for this test. If it does then I'd go back to checking the CTS value that the ECM is seeing.

As for the injectors, probably bad. The Multecs short out which at this age, if original, are on their last legs. This is one item that I don't even bother to test before replacing. Anything else I try to prove one way or another before swapping parts, but Multec's, gone.

RBob.

 

Is the pressure switch wiring over by the.. ac compressor? Or whatever the silver cylinder is. If its that circular looking connector over there then its just hanging there. I dont believe its being grounded and there is not anything jumping the two wires together.


Side question: What type of injectors would I replace the originals with? I pulled the fuel rail, it looks like 4 of the 6 are original. The other two im not sure on the make / model. I might as well just replace all 6 again so that im sure they have the same operation.

 

A/C pressure switch is on the passenger side (US). I think it is on the hose with the small silver can on it. Not on the large can attached to the suit-case.

For injectors my preference is Bosch. Can try Linder Tech and Fuel Injection Connection to see what they have.
http://lindertech.com/
http://fuelinjectorconnection.com/shop/

RBob.

 

that lindertech website doesn't looks a bit risky. A set of injectors for 200 is a heck of a deal though.

Gonna hit the ac tomorrow and see if i cant get this fan workin with your advice. If not, back to square one.

 

fic.com lists injectors for 3.1 for $149

http://fuelinjectorconnection.com/sh...&productId=186