Problems with reman Q-Jet: round two

[SilveradoDude]

Ok, I got a new reman Q-Jet.
It runs a lot better out of the box than the last one but it still needs some adjustments I just don't know which ones.

symptoms.
- idling way too high
- dieseling
- white smoke

What adjustments do I need to do to get this carb running right?

(85 C10 305 - 84 ignition)

[zac]

Whats the carb number? It will start with a 170. Electric choke? Does it have the idle mixture screws on the front down on the baseplate or just a couple plugged holes? A couple pics would be helpful.

[geezer#99]

Idling high can be caused by a rich choke setting. Lean yours down or adjust the high idle screw.
Dieseling is caused by a too far open primary throttle. Your high idle is likely causing that.

Where is the white smoke seen?

[SilveradoDude]

Originally Posted by zac

Whats the carb number? It will start with a 170. Electric choke? Does it have the idle mixture screws on the front down on the baseplate or just a couple plugged holes? A couple pics would be helpful.

17059205 looks like a 79 Chevy (and a manual).
Electric choke, yes it has mixture screws.

[SilveradoDude]

Originally Posted by geezer#99

Idling high can be caused by a rich choke setting. Lean yours down or adjust the high idle screw.
Dieseling is caused by a too far open primary throttle. Your high idle is likely causing that.

Where is the white smoke seen?

The tailpipe. Also, I no longer run the ECM (85), I use and 84 distributor and a pre-electronics carb.

[geezer#99]

Originally Posted by SilveradoDude

17059205 looks like a 79 Chevy (and a manual).
Electric choke, yes it has mixture screws.

Is that a hot air choke carb converted to electric?

[SilveradoDude]

Originally Posted by geezer#99

Is that a hot air choke carb converted to electric?

No.

[zac]

Ok, you have to get the curb idle down to normal. That can’t happen until the engine is warmed and carb off the fast idle cam. The fast idle cam system has an adjustment also, but dont touch that unless you have to. Curb idle is adjusted from the front on the drivers side. If you back the curb idle screw all the way off to where it’s not touching the linkage at all, it’s most likely an issue with the choke adjustment. The problem is that many reman carbs have the choke cover screws removed and rivets in their place. Which does yours have? Also, verify with a volt meter that you have 12 volts to the choke wire. If you don’t you’ll never get the idle speed down.

[SilveradoDude]

Originally Posted by zac

Ok, you have to get the curb idle down to normal. That can’t happen until the engine is warmed and carb off the fast idle cam. The fast idle cam system has an adjustment also, but dont touch that unless you have to. Curb idle is adjusted from the front on the drivers side. If you back the curb idle screw all the way off to where it’s not touching the linkage at all, it’s most likely an issue with the choke adjustment. The problem is that many reman carbs have the choke cover screws removed and rivets in their place. Which does yours have? Also, verify with a volt meter that you have 12 volts to the choke wire. If you don’t you’ll never get the idle speed down.

Ok, you covered a lot of ground there. So are you saying the first thing I need to do tomorrow morning is check if I am getting 12 volts to the choke wire by turning ignition to power on? And then if I am then go to adjust the choke (warm the truck first)? the choke cover has screws so then you are saying work on adjusting the choke next? So don't touch the mixture D screws?

[zac]

Don’t touch the choke adjustment yet. With the engine cold, you step on the accelerator once to set the choke. The choke should be closed. Crank the engine and when the engine fires up the choke blade should open a crack. Does this happen? Engine should be on fast idle now, after a short period you bump the accelerator pedal and the idle speed should drop, but not all the way down. The choke blade should be opening on its own as the electricity through the choke coil heats it up. Eventually by tapping the accelerator you should be able to get the idle down to normal, where the drivers side of the linkage is touching the curb idle screw and can finally be adjusted. All the choke and fast idle stuff happens on the passenger side. Start the truck just like I said and watch what happens. No pumping the gas pedal! Post what happens.

Quadrajets are the best carb ever made but the absolute hardest to work on. And as they get older I’m having more trouble making any of them work right, personally. I’m telling you not to pump the gas but my ‘79 sometimes takes an extra shot of gas when it’s really cold because my choke isn’t completely dialed in. I have a glovebox full of choke coils and haven’t found the right one. And the carb is off an ‘85 motorhome with a 454...if you can get your carb adjusted properly it will be worth it. Just takes time and patience. I will try to post some pics later.

[zac]

And yes, start with turning the key on and checking for 12v at the choke wire. Otherwise this is all pointless

[SilveradoDude]

Originally Posted by zac

Don’t touch the choke adjustment yet. With the engine cold, you step on the accelerator once to set the choke. The choke should be closed. Crank the engine and when the engine fires up the choke blade should open a crack. Does this happen? Engine should be on fast idle now, after a short period you bump the accelerator pedal and the idle speed should drop, but not all the way down. The choke blade should be opening on its own as the electricity through the choke coil heats it up. Eventually by tapping the accelerator you should be able to get the idle down to normal, where the drivers side of the linkage is touching the curb idle screw and can finally be adjusted. All the choke and fast idle stuff happens on the passenger side. Start the truck just like I said and watch what happens. No pumping the gas pedal! Post what happens.

Quadrajets are the best carb ever made but the absolute hardest to work on. And as they get older I’m having more trouble making any of them work right, personally. I’m telling you not to pump the gas but my ‘79 sometimes takes an extra shot of gas when it’s really cold because my choke isn’t completely dialed in. I have a glovebox full of choke coils and haven’t found the right one. And the carb is off an ‘85 motorhome with a 454...if you can get your carb adjusted properly it will be worth it. Just takes time and patience. I will try to post some pics later.

Ok, confirmed 12 volts to the elec. choke (well 11.58). Engine cold. stepped on the accelerator once. Choke appeared "closed" (small gap). bumped the accelerator again and the idle speed DOES NOT reduce, seems to stick. When I manually fiddle with the accelerator pump lever it went down. Also a small amount of gas near accelerator pump lever. The truck is idling so high (1000 rpm at idle) I can't get it any lower. curb idle screw is all the way out. Need to get these RPM's down. No smoke today though. Still dieseling if it runs for a few minutes then shut off.

[zac]

Probably a choke issue. Loosen the 3 screws on the choke cover and rotate it a bit clockwise 1/8 of a turn or so, and see if it helps. Your choke may be labelled so that you are turning it toward "lean" or "leaner". Not all are marked. This should help you get it off the fast idle cam. The fast idle cam has three steps. I am posting a picture of the fast idle cam lever or "follower" behind the choke housing. It is more or less straight up when you start on full choke, as pictured. On the second step it drops part way down, forward on the carb. On the third step you are technically all the way off the fast idle cam and the follower drops all the way down forward. In your case you may be able to push the lever forward off the highest step with your finger or a screw driver until you get the choke adjusted.

Getting the choke adjusted is a trial and error procedure these days, unfortunately. There is a technically "correct" way to do it, but the fact that you bought a reman carb for "your truck" only means that it should bolt on and the linkage should hook up. There were a huge number of variations of these carbs and anything you get now is just a pretty rough approximation of what is supposed to be on your vehicle. You need to have the choke set so that the blade closes all the way when you set the choke, but it needs to not be set too rich so that you can get it all the way off fast idle so that the driver's side linkage is touching the back of the curb idle screw, as pictured. The tick mark on the choke cover may or may not be in the range of the little index bumps on the choke housing. The line may end up all the way left or right of them when you are finally set, but at least it gives you a reference. Once you get this ballparked you should move on the idle mixture setting.

[SilveradoDude]

Ok, I think I got it. I snugged the carb down (maybe had a small vac leak, then I moved the timing back down close to factory 4 degrees BTDC. the idle looks close to perfect. Will drive and let you know.

[cadillac_al]

That's not much timing. You are going to lose some efficiency. It sounds like your choke isn't opening and getting off fast idle. In Zac's last post, the 2nd pic shows the lever of your fast idle cam. That needs to drop down to get off of fast idle. You can push it down with your finger to hear the difference.

[SilveradoDude]

Originally Posted by cadillac_al

That's not much timing. You are going to lose some efficiency. It sounds like your choke isn't opening and getting off fast idle. In Zac's last post, the 2nd pic shows the lever of your fast idle cam. That needs to drop down to get off of fast idle. You can push it down with your finger to hear the difference.

I did that. I heard no difference. Took the truck out around the neighborhood. It runs decent. Idles just a hair high (by ear - it was doing 810-820 by tach) when I button her up. Still diesels a little bit which bothers the hell out of me. I need to stop this dieseling..... I think my Idle Stop Solenoid is bad.

[zac]

It’s dieseling because the idle is way high. Did the fast idle cam lever drop down all the way forward? Is the choke all the way open when it’s warmed up? Have you located and adjusted the idle screw on the drivers side?

[SilveradoDude]

Originally Posted by zac

It’s dieseling because the idle is way high. Did the fast idle cam lever drop down all the way forward?

Yes.

Originally Posted by zac

Is the choke all the way open when it’s warmed up?

Yes.

Originally Posted by zac

Have you located and adjusted the idle screw on the drivers side?

Yes.

[SilveradoDude]

..........

[geezer#99]

Turn the high idle screw down.
It’s found right under the electric choke.

[SilveradoDude]

Originally Posted by geezer#99

Turn the high idle screw down.
It’s found right under the electric choke.

I did that.

[geezer#99]

What did you use for a gasket between the intake and the carb?

[cadillac_al]

After all that, your throttle plates should be closed pretty tight. I wonder if the secondaries are sticking open a little. I had a couple that the secondaries would hang up. I also had a couple vehicles that I couldn't get idled down and I resorted to ported vacuum for the distributor. Those could have been vacuum leaks that I couldn't find.

[zac]

If everything is working correctly and more or less adjusted we’re down to vacuum leaks most likely. They can even be internal.

[SilveradoDude]

Originally Posted by geezer#99

What did you use for a gasket between the intake and the carb?

Standard FelPro gasket. (new) I sprayed carb cleaner around the gasket and didn't receive any rise in RPM's.