Electric Choke - HELP

[PHOENIX]

OK guys I have a 1904 Edelbrock Q-Jet.
Its around 4 years old or so.
Its seems as if the electric choke is sticking or not turning off.
I dont know whats going on.

I had trouble getting my idle speed lower.
I had the idle speed screw all the way out and the idle was still like 900 rpm.
So I figured the choke was still working, even after long warm up.
So I started adjusting the choke idle speed and lowered it down to like 700 rpm from 1000 rpm or so.
I was then able to lower my regular idle speed to 700rpm.
But after a short drive the idle speed returns to 1000 rpm or even up to 1200 rpm.
I unhooked the oil pressure switch near the oil filter awhile back.
Does this have anything to do with the electric choke?
How do I test the electric choke to see if it is working properly.
I have not yet checked if 12v's is being provided to the choke or not.
It used to be that I could start the truck, idle speed would be about 950rpm, I would drive about 2 miles and my idle speed would return to 700 rpm.
Or I could rev it up a little high and the idle speed would go down to 700 rpm.
It was great for cold mornings.
It doesnt get that cold here.
I dont even really need a choke, but I would like to keep it working anyway.

Also when the choke is competely off, is the plate above the primaries (?) straight up and down, or is it like a 45 degree angle.
It seems like it moves from closed (blocked off) to slightly open.
When I move the plate by hand to straight up the idle speed drops to where I want it.
Also when I play with the choke linkage everything is very smooth.
Nothing is binding, getting gunked up, sticking, etc. Smooth as can be.

Does that oil pressure switch above the oil filter have anything to do with the electric choke?
Anyone have an idea of what my problem is?
What should I check?

Thanks

[blitz'd]

Check the 12v power source and fuse. My truck was doing the same thing after i pulled the fuse for the choke cause i didnt have any more and blew the one for my parking lights and had to get home.

[86-C10-V6]

IF you remove or disconnect it, there will be no power to the choke and it will stay active.
If what you say is true, you should have the choke indicator light showing on your dash.

['85Silverado]

I'll second that...the electric choke won't activate until the engine is running (oil pressure switch). That way if you leave the ignition 'on' and don't start it, the choke won't heat-up.

[MylilBowTie]

Why is it again that the choke light will come on? Does it come on to let you know its working or something else? It comes on when I turn the ignition to the run position then when I start the engine it goes out.

My choke will only work when it really wants to do so. Lately I have been having to pump the gas pedal quite a few times (about 7 times) to get it to start in the cold mornings. It will start for a second then die right away have to pump a few times then it will fire again and usually run but not always. If it doesn't run it just dies out very quick, like starting it and shutting off ignition (taking about 1.56seconds). If I dont do anything to it and just try to start it, all that happens is will spin over and not fire. With the gas pedal barley tapped to set the choke or not. I have 60 psi oil pressure when it starts up. After it starts and its warmed up all I have to do is tap the ignition and it fires right up.

[PHOENIX]

Well I dont have the factory gauges anymore and I didnt hook up a choke light. So I dont know what the choke light it doing

I did hook that switch back up and noticed that when the truck is running the choke has power now. I am about to go play with it now.

I want to see if I understand this correctly:
Power goes to the oil pressure switch
When the truck is running (has oil pressure) the switch allows power through
The power goes to the choke and heats up a coil (?) which once heated opens the choke for normal driving.

So is there supposed to be power at the choke the entire time the truck is running? Or does the pressure switch only send power through under a certain pressure or over a certain pressure or in a preset pressure range?

If the choke coil stops getting power for some reason (lets say a blown fuse or bad pressure switch) during driving, will this cause the choke to close again? I guess what I am saying, does the electrical power hold the choke open?

Thanks again guys, I appreciate the replies. Ill let you know how thing go later. I am about to go and set the choke with the pressure switch hooked up again and see where it gets me.

[badone07]

You got it. No power to choke, choke closes. Has to have power to it, while the truck is running, to remain open.

[85Silveradoin04]

Originally Posted by '85Silverado

I'll second that...the electric choke won't activate until the engine is running (oil pressure switch). That way if you leave the ignition 'on' and don't start it, the choke won't heat-up.

I've tried wiring my elec. choke to the oil pressure switch. When the engine is running, the oil pressure gauge shows no pressure. When I remove the wiring, the pressure is being seen as it should. I've only got one wire that goes to the switch. Could this be the problem. I've been running the choke with a constant 12v from the batt term on the HEI so needless to say, It opens regardless.


badone07, if it was during driving it would have to depend on what the temp is right for the the choke to close (assuming it was already opened)? I mean, the spring could eventually warm-up (or stay warmed up) because the engine bay temps are high, right?

[ElGracho]

Read this thread. We've been through this a few times...

http://67-72chevytrucks.com/vboard/s....php3?t=123429

[mckpaul]

There are two devices on the engine that look at oil pressure. One is a sending unit on top of the engine just behind the intake manifold next to the firewall and distributor. It's a canister looking thing with one terminal on top. This one sends a signal to the gauge on the dash. The other is the switch near the oil filter with two terminals. It's open when the engine is not running, closed when the engine is running. It sends voltage to the choke. On the stock dash, there is a choke light, one of the bulbs that you change by removing the little black sockets on the back of the dash, same kind of bulb as all the rest. It's tied into the choke circuit, there's a diagram on the link that Joe provided. The choke light comes on if the oil pressure switch is open and the choke is not getting voltage. The choke light finds it's ground back through the coil on the choke. Yes, the coil is getting some voltage since it's in the circuit with the bulb, but it's in series with the bulb, and the bulb is getting the lions share of the voltage, so it really doesn't get heated up. When the oil switch closes, the light has (+) 12V on both sides so it goes off and the choke gets the full 12V that it needs to heat up.

Even with no voltage to the choke, when the motor starts, the choke will open slightly as Eddie mentioned, because of the choke pulloff vacuum pod on the carb. The choke has to open slightly immediately after the motor starts so it will run. There's no way the electric coil can open the choke quick enough since it has to heat up. But as soon as the motor starts there is vacuum, so they used vacuum for the first action to open the choke enough for the motor to run. But the slow action of the electric coil heating up and slowly opening the choke works well with fact that the engine takes a little while to heat up as well.

Us 'not so young' guys had to deal with a choke coil in a housing that was bolted to the intake manifold next to the carb. It used heat from the engine to heat the coil that pulled the choke open. But that was back when you didn't have to have a garage full of computers to make your car run. Man I miss those days.....

How's that for a long winded description???