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Carburetors Carb discussion and questions. Upgrading your Third Gen's carburetor, swapping TBI to carburetor, or TPI to carburetor? Need LG4 or H.O. info? Post it here.

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Old 04-19-2007, 06:58 AM   #1
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Choke thermostat.

Hi All,If i have the choke thermostat out,ie, the type with the metal coil,if i apply
power to the connector where the choke power wire goes to normally,should it heat up or should the coil move at all,as i tried this and nothing happened.I checked at the coil itself with a multimeter and got 12 volts so i dont know if its working or not.I'm just trying to work out my current problem and eliminate things as i go.Thanks for any help.

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Old 04-19-2007, 10:10 AM   #2
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Re: Choke thermostat.

The coil is bimetallic. When it has power applied to it, the 2 metals heat up at different rates and it causes the thing to spin slightly in turn opening/closing the choke plate.

If you have a full 12v on the wire going to the choke, chances are the choke has bit the dust. Especially if it doesnt feel warm(or hot) to the touch after a drive.
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Old 04-19-2007, 12:05 PM   #3
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If you take the thermostat off of the carb, and apply 12 volts to the terminal, you have an open circuit.

It needs a complete circuit, so you have to ground the coil as well.

If you did that and it didn't move, then you've got a defective thermostat.

Assuming this is a stock carb, that is, which only has one wire and is grounded through the carb. Aftermarket carbs/choke thermostats often are 2-wire.
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Old 04-19-2007, 07:31 PM   #4
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Re: Choke thermostat.

Does the choke thermostate get a signal from the engine temperature sensor, or will the bimetal coil heat and open the choke regardless of engine temp?

How do the engine / computer communicate with the carb choke?

What happens if one heats up before the other? Like defective choke coil, or too cool a thermostat or defective engine temp sensor and both the carb and engine are not in sync with regards to temperature.

These questions are in reference to the feedback carb system.

Thanks!
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Old 04-19-2007, 11:43 PM   #5
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The computer has nothing to do with it. It's in the alternator - when there's enough voltage from the alternator, it kicks a relay that powers the choke thermostat.
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Old 04-21-2007, 05:27 AM   #6
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Re: Choke thermostat.

Hi,I forgot to ground it,so i did that and the coil moved around about 1/4 inch and got warm as well so it works ok i assume.Now i'll have to keep checking things out until i find out what's wrong with the thing.It's defininitely something to do with the carby as far as i can see,i just have to work out what.

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Old 04-21-2007, 07:34 AM   #7
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Re: Choke thermostat.

Aside from the "does it heat up?" test you also want to test it's resistance. You must do this when it's cold (room temperature)- not heated up. You should see 5-10 Ohms resistance on a good one. 20 Ohms max. If it's beyond 20-25 ohms it's getting "weak" and won't work reliably.
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Old 04-22-2007, 05:14 AM   #8
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Re: Choke thermostat.

Okay,i tested the resistance and got between 13 and 14 ohms so it's probably
not bad for a original one.

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Old 04-22-2007, 05:14 AM
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