Quadrajet choke adjustment questions

[CactusCurt]

Ok, more detail to be added later but here's the skinny.

The electric choke on my Qjet on my stroker never worked right , so it was disabled. Rig is only used in the summer, so not that big a deal but on the fix-it list and currently underway. The carb is from Jet and is basically new.

So after putting it on the bench and pulling the choke housing and linkage and putting it back together the way I *think* it goes, this is where I'm at.

To cold start, she won't close the choke blade by moving the throttle until I adjust the choke blade. So turn the choke adjustment dial (black bakelite dial in choke housing)to snug closed but not tight. Starts like a champ, choke pull-off appears to be functioning and adjusted correctly.

BUT, after running on high idle for plenty long (10 minutes), the bi-metal coil hasn't opened the choke blade all the way to the point it falls off the high idle adjustment. During this process I end up having to tinker with the high idle speed, whose adjustment mechanism seems to be working as intended.

If I push down on the high idle cam with my finger, I can feel ever so slight pressure (spring?) wanting to push it back up. However, I can't "release" it with my finger, so I have to go back to the choke adjustment and open it (15 or 20 degrees of rotation?) until it falls off the high idle adjustment and onto the curb idle adjustment. I can bang on the throttle all I want (clear to WOT), but that doesnt kick it off the high idle either. I can't figure out what's keeping the fast idle cam from falling.

I will go out when it warms up and go thru the process again detailing the gymnastics i have to go thru - including pictures! I'm getting pretty good at it.

This thing runs PERFECT except for the choke. I don't want to have to replace it with some junk edelbrock or TBi.

If you can walk me thru this, I will send you a box of beer cans.

[Truckman]

Mind you it's only been 23 years + since I worked on one of these and my memory comes and goes at times...So, is the heat tube from the heat riser valve intact from the exhaust manifold to the choke heater, and are there any kinks or rust pockets in it?...Are you getting actual heat all the way to the coil inside the bakelite housing?...Is the coil reacting as it should to the presence of heat?...If not, is the heat riser valve working, or is it always closed?...Do you have either headers or an intake manifold that does not permit exhaust heat to cross from one bank to the other?...Check all that and get back to us......Ben

[CactusCurt]

Electric choke.....not divorced or exhaust heat activated. Yes, bi-metal coil is causing choke plate to open as intended - but not far enough?

Only thing I won't be able to get is vacuum reading, but that shouldn't matter? No leaks, she's pretty clean. Like I said runs perfect when I manipulate the choke manually.

It's just like the high idle cam is ever so slightly being held by something that's not allowing it to drop. It seemed to work perfect on the bench and I don't have any linkage interference that I can find. It's almost like I don't have the range of motion I need in the bi-metal spring.

When it gets up to around 32 degrees in a couple of hours I will go back out and monkey with it. I apologize in advance for the PTSD remembering qjet diagrams is certain to cause.

Here's a overall pic to give you a feel for what we are looking at. You don't need to wash your hands after working on it Detail to follow.

[Truckman]

Here's a overall pic to give you a feel for what we are looking at.

Looks like headers, correct?...Is there any crossover heat?......Ben

[CactusCurt]

Looks like headers, correct?...Is there any crossover heat?......Ben

Yes headers, but no "heat riser" into choke housing, the movement in the bi-metal coil spring is all created by a switched 12v connection. Once the key is turned on, the coil holds the choke plates open as long as the key is on and electricity flows to the coil. Ground is thru the carb body. Much cleaner than the nasty exhaust operated one - and you don't get fouled up with that tiny vacuum orifice. All of that stuff appears to be functioning.

I believe this is what we could call a modern q-jet.

[Truckman]

Once the key is turned on, the coil holds the choke plates open as long as the key is on and electricity flows to the coil.

I understand that part, but I take it with headers you don't have one exhaust bank closed with (I forget what that valve was called) to send exhaust heat through a crossover passage in the intake manifold to heat it...I think the choke/high idle discrepancy will just be a matter of adjustment...Maybe Mastertech will see this and stop in......Ben

[FredK]

Is it 12 volts at the choke?

Like Ben it's been 30-40 years since I messed with those.

[CactusCurt]

Ok, here we go.

First pic is after "blipping" the throttle to close the choke plate. You can see there is a slight opening. No start, wants to be closed all the way.

Note that immediately upon starting, the pull-off gets vacuum and cracks the choke plate. I can't watch this while I crank, but you can tell if it's in adjustment because it goes smoothly to high idle without a bunch of blubbering.

Note the position of the choke. As I said, this is a no start position. (On edit: I can actually get it to start if I pump the throttle a zillion times to basically flood it enough to get a mixture rich enough to start. Thats not right and is a pita, hence I am finally getting around to fixing it)

[CactusCurt]

Ok, so now I need to adjust the choke to this position (black dial) to fully close the choke plate. You can see about where things are in the first pic.

Second pic shows engine started, choke position, and pull-off under vacuum. Starts dependably and almost instantly with choke set here.

[CactusCurt]

Ok, so here we are after 10 minutes during which time I fool with the high idle speed by backing of it's adjustment 2 full turns. This doesn't seem right. First pic is high idle linkage.

Second pic shows how far the choke plate opens after it has reached full operating temp (coolant temp - intake will continue to warm but I'm not having issues with that). Note the position of the high idle cam.

The high idle cam is supposed to fall, kicking things back to the curb idle screw. If I push it down as shown in third pic, it pops back up if I blip the throttle. Again, not supposed to do that.

[CactusCurt]

So finally, if I want the choke plate to "lock" open, I have to manually adjust the choke (black dial) back to about where we started. Note the position of the choke (black dial). It's worth noting that I get very close to having the high idle cam dropping all the way because the secondaries work and they would be locked out if there was still too much choke. I think.

As I said, she runs VERY WELL and I'm not messing with anything except the damn choke. This is a nuisance where something is very close, but just not quite right.

And yes Fred, we have 12 v at the connection.

It's still better than fuel injection.

[Sandman]

My last “build your own” was a Ford 351m.. I gave up and went manual.. worked like a dream!

But then.. I have refined slackerdom to an art form..

[CactusCurt]

My last “build your own” was a Ford 351m.. I gave up and went manual.. worked like a dream!

But then.. I have refined slackerdom to an art form..

I'm so with you. This '69 bronco came with a manual choke AND a dash mounted throttle cable, both still functional (but disconnected). The ONLY reason for this brain damage is not having to manage the high idle warmup. With a throttle control I don't even need that.

This is more of a excercise for me because I'm stubborn and bullheaded. I rarely choose the easy path.

[Truckman]

Curt, I won't trust my memory any further than I already have except to say just keep tinkering and adjusting until you hit the right combination...If I had it here I might be able to let my hands do the remembering, but even that is a big "if"...I still can't help but think the lack of crossover heat under the carb has some effect on your problem given where you live and the cold climate, but that is not easily fixed after installing headers...You might try PM'ing Mastertech to see if he'll come out of hibernation......Ben

[CactusCurt]

The more I think about this, the more I think my bi-metal coil may be shot. It only lacks 1/2" or so between the two settings. And it never did work, which is why I'm in this boat. I'm not sure there is a way to test them, but I bet I can have one on the porch before I figure it out.