Electric choke - how exactly does it work?

[riquiscott]

One of my students has an Edelbrock carb with an electric choke on her Charger, but the power and ground wires to the choke are disconnected. Does this mean that her choke is always on, or always off? Inside the choke housing, there's a coiled metallic strip with one end connected to the choke activating rod. I'm particularly interested in how the choke works, because I bought the electric choke kit for the Edelbrock in my car, but haven't installed it yet.

I'm assuming that with the engine cold and the power connected to the choke, the coiled strip is positioned so that the choke is active, then as the car heats up, the coiled strip moves, disengaging the choke.

Scott Gardner

[pishta]

That is it. The spring is coiled up cold, holding the choke plate closed and wedging the fast idle cam off its stop. As the heater (electric or exhaust driven) heats the spring, it expands and starts to uncoil, moving the choke plate to the open position and letting the fast idle cam return to its stop. Upon full heat, the choke plate is vertical and the fast idle is on its stop and it is wedged there by the linkage. So when you pump the gas once when it is a cold start, the linkage releases the coil back to its natural coiled position and it snaps the choke closed and brings the fast idle cam off its stop again. the amplified vacuum the choke plate produces draws more fuel out of the venturis and causes a rich condition that is easier to combust in a cold cylinder and the fast idle setting allows the motor to idle with that restricting choke plate.

[MoparMarcIdaho]

I would imagine that someone has turned the adjustment lean so it stays open.Might just need to be hooked back up.They take a pretty good amount of voltage so go to accesories in the fuse box and run a lead out to it,and of course it must be grounded to the motor someplace,usually a carb mounting stud.Put your hand on it and you will feel it get warm when its working.

[riquiscott]

Thanks for all the replies - I took my electric choke (not installed in the car yet) and powered it directly off of the battery to test it. Sure enough, after a few minutes, it got warm and the coil strip started to move, eventually moving through about an inch of travel.

Since her electric choke wires are disconnected, I'm assuming that her choke is probably activated all the time, and someone has adjusted the carburetor lean as heck to compensate. This makes sense because even though her car is hard to start, it runs well enough once it's warm. I don't know what kind of gas mileage she's getting, though. I'll reconnect the wires to her choke and make sure it's adjusted properly, then we'll break out the metering rods and richen the carb appropriately.

I'm glad I understand how the choke works now. I initially thought the engine heat caused the coiled strip to expand and contract, so I was a little confused as to what the wires were for.

Scott Gardner

[ehostler]

Originally posted by MoparMarcIdaho
They take a pretty good amount of voltage...

Actually, they take no more voltage than anything else in the car. They take about 5 - 10 amps of current.

[MoparMarcIdaho]

But a friend of mine hooked his up to the positive side of the coil and it created some problems.

[ehostler]

You should never hook anything up to the positive side of the coil (except the coil hot wire). If you are running the chrysler electronic ignition or any after market ignition system, you will damage the ECU and possibly whatever you attached. I know that my Jacobs computer sents up to 600 VDC (low current) down that positive lead during hard acceleration.

Also, note there is a difference between volts and current (Amps).

[MoparMarcIdaho]

And it doesnt help ballast resistors either.

[John Kunkel]

One other thing, there is a threaded fitting on the choke housing that must be hooked to a supply of clean fresh air. If the fitting is capped off, as often happens, there will be no air flow through the unit and the coil will overheat; shortening its life.

[horatio102]

hm

On my buddy's truck when he bought his new 318 (from a local shop) it came with the 2bbl intake, and he wanted to go with a 4bbl so he bought the manifold and I loaned him one of my edl 750's that I've got lying around. Yeah yeah, wrong carb for the job, but it ran enough to get the job done until he bought his own carb.

Anyway, it's an electric choke carb, and he didn't hook it up at all, but it seems that the engine heat was enough to get the choke to open as the engine warmed up.

On my truck, I'm running a holley 600, and the other day the choke wire fell off. I realized this after driving down the road my truck suddenly went to fast idle and I couldn't get it to go back. It also dieseled once when I stopped at the gas station to fill up. Are holley electric chokes more insulated from ambient temps so they'll coil back up if the current shuts off?

[MoparMarcIdaho]

was for a ford van 460 and it had a large pull off diaphram and drew air through it from internal vaccum.They vary depending on year.My favorite has always been manual conversion kit.Then you know when its on or off.