AMC Eagle Den Forum
The Mighty 258 => Fuel Systems. => Topic started by: 85AmCfreak on December 16, 2011, 12:43:58 AM
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I am trying to figure out why my choke is not working. Is the wire that leads to the choke thermostat supposed to have 12 volts with the key on and the engine off?
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No, the choke is tied in with the oil pressure switch. When the engine is running is the only time the choke should have 12 volts. It's so that if you sit in your car with the key on listening to the radio, the choke doesn't heat up and open up, while the engine is still cold, which would make the car hard to drive when started.
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I know that after my car starts, the choke stays closed for a while and slowly moves open. It can run with it all the way open, but I think it has better drivability when it stays closed and opens slowly. As you said, it was probably mainly just so you would be able to get it started.
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The choke also actuates a cam to keep the idle up a little until the engine warms up so that you don't stall at red lights.
The oil pressure switch triggers two things - the choke and an a relay for the electric heater under the carb. As said, it's for cold drivability, but also so that the heating elements in the choke and manifold don't draw extra power when the engine isn't running.
One of the tabs on the oil pressure switch will have 12v when the ignition is on. One should ground until pressure builds, and the other should have 12v with pressure.
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Where does the wire from the heating element in the intake manifold hook into ?
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It plugs into the intake manifold heater relay which is by the starter solenoid.
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And the relay grounds to a temperature switch on the intake that turns off the manifold heater, but not the choke heater, when the car warms up.
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Everyone is correct that has given advice about the choke and manifold heater. Great job all.
The choke is a very simple device that will make everything miserable if not working and set up properly. Another way to wire the choke and eliminate some issues is to wire the choke off of the starter solenoid in the run position. MOST fuse panels will also have a reserved CHOKE block that already does this for you. Sometimes the oil pressure switch doesn't work right and causes choke issues.
Also, a sticky idle cam will cause major problems.
I personally prefer to add an additional ground wire to the choke retainer housing so i know its grounded properly.
A few minor additions will really increase proficiency of your choke system.....
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Thank you all for the suggestions I wired the signal wire from the relay to the solenoid works great thanks alot