Quadrajet rebuild... Need help

[dougbfresh]

I think the anti diesel thing was about closing the choke on shutdown to keep fron DIESELING on shut off.

[olddog]

Here is what I remember of what I may have once understood:

They went to ported vacuum on the distributor advance. Idling the engine with the timing retarded causes much more heat in the combustion chamber and lights off the catalyst quicker (and keeps it lit idling in cold weather). Thus better emissions.

With retarded timing at idle the throttle plates must be opened more to keep the idle rpm the same as it would have been had they used manifold vacuum. In short the throttle has to be more open, at idle, when ported vacuum is used for the advance.

Here comes the problem. With the retarded timing at idle the combustion chambers run extremely hot in stop and go traffic. Now you turn the engine off. With the throttle plates more open than the pre-ported vacuum days, there are hot spots in the heads that light the fuel (much like glow plugs in a diesel) and the engine continues to run.

The solution was to close the throttle plates when the key is turned off. Look at the anti diesel solenoid in the schematic. It shows the vacuum line going to the ILC (something to do with the idle). The choke is on the other side of the carb. It wouldn't make sense to close the choke, as that would dump a bunch of raw fuel into the manifold that would not get burned.

[danny]

the solenoid was to keep the idle up until the engine was shut off and then it would allow the throttle plates to completely close.

[olddog]

Originally Posted by ziolo

From what I understand and read the Diesel solenoid runs to the Idle Load Compensator which is only used to raise the RPM's once the AC is turned on.

I know some carb cars in the 80's kicked the throttle more open when the AC kicked on to keep the idle speed the same as the AC clutch kicked on/off. The actual plunger that moves the throttle may have multiple functions. The anti diesel solenoid does close the throttle, when the engine is turned off.

In the end days of Carburetors and emission controls, it became near impossible to do what needed to be done and keep it all working. The manufacturers certainly did not want to go to the costs of EFI, but in reality it became cheaper when the big picture was looked at.

All I am going to say is that those year cars were extremely complicated. If you want to start taking stuff off that you have know idea what it is doing, have at it. Just remember there are very few mechanics that remember this old stuff and your not going to easily find help when you get it screwed up.

PS
Ziolo - I can tell you are doing your home work and trying to understand all this. I'm sure I came off a bit arrogant and condescending. I don't mean to be a jerk here. Back in the days when this stuff was new, I never met a professional factory trained master mechanic that understood how all that crap worked well enough to tell you what you are asking. I just don't want you to get in over your head. At least take a million pictures and notes and drawings, so you can put things back to where they are.

[dougbfresh]

Like I said before, these carbs are not worth fooling with once they go. You can try to get it working again but just that complicated choke adjustment will make you insane. They also had their idle mix adjustment glued shut at the factory-many guys drilled out the glue so they could make idle mix adjustments. The other thing to watch for is the throttle plates also get sloppy over time and need re-bushing to keep them from leaking, once they do this, you'll never get it to idle correctly.

Put the carb on and try to adjust it but don't wish for too much.

[KA9MOT]

Originally Posted by BigBry

http://www.youtube.com/watch?v=ssdhPqWnS6I

Thanks for the Link BigBry. I was unaware you guys were on YouTube.

[BigBry]

We had someone doing it, and I never really looked at it much since I se the shows so many times already. I am going to start posting some of our meatier segments though. Hopefully if we can get some of these segments on to other car boards people will start trying out our show.

[dougbfresh]

The E4MC is more complicated than a typical Qjet, the choke it CRAZY complicated for emissions and trying to get it set just right to start and run well cold is tough.

[KA9MOT]

What is an EM4C?

[dougbfresh]

Originally Posted by Beefy's Bronco

What is an EM4C?

One of the last versions of the Q-jet with several solenoids to try to make it do what a carb can't do well. The choke is/was a 3 stage setup:

1) Closed for startup
2) A solenoid opened the choke partially soon after startup to reduce emissions.
3) A regular thermal choke that would open the choke all the way after warmup.

Getting #2 just right is hard if you try to follow the manual, there is so much slop in the choke that you can't do it "by the book" easily-trial and error works better but you can only try it when the thermal choke is cold.

[KA9MOT]

Originally Posted by dougbfresh

One of the last versions of the Q-jet with several solenoids to try to make it do what a carb can't do well. The choke is/was a 3 stage setup:

1) Closed for startup
2) A solenoid opened the choke partially soon after startup to reduce emissions.
3) A regular thermal choke that would open the choke all the way after warmup.

Getting #2 just right is hard if you try to follow the manual, there is so much slop in the choke that you can't do it "by the book" easily-trial and error works better but you can only try it when the thermal choke is cold.

Grassyass Amigo!

[ziolo]

First off, thanks for the comments guys... olddog... I welcome what you have to say and i dont consider it arrogant and condescending... Believe me when i say this... If this was my car i'd do things the way they should be done, everything would stay hooked up like it should but its not my car. People are always rushing me to try and fix things that most of the time wont even necessarily solve the problem 100% anyways.. I honestly would rather rebuild the engine and make sure everything is up to par cause things are leaking here and there but my uncle doesnt want to... So i can only work with what i got... That being said... Its not that i want to remove everything, its just that I'm not even sure what works and what doesnt.

So lets start with this. The carb thats currently on his car doesnt even have the ILC on it, it must have been removed (by who i dont know)... I thought it was only for the AC to kick up the RPM's. The one i rebuilt has the ILC on it except it has 2 ports on it to hook up vacuum lines, but the diagram only shows one line going to it.. Not sure which one i should use.

Im not sure if the DPS sensor or the anti diesel solenoid work, nor do i know how to test them.

As far as the many valves in the diagram, i dont know which work or dont work.

I know this much, it cant be any worse than it was... Trust me... Half the stuff was looped around every which way. Vacuum lines capped of and stuff not hooked up... I finally got the car tonight and will have it through the weekend so ill see what happens. Wish i knew guys like you that lived around me that could help out, but i dont..... So ill just have to have at it. Thanks.

[ziolo]

I can say im a little freaked out and not sure what to do next. Let me fill you in on what ive done so far.

Mind you this is still without putting the rebuilt carb on. The DPS sensor wasnt hooked up nor was the EFE valve. So I went through all the vacuum lines and hooked them up the way they should be. The only thing I didnt hook up is the ILC (cause its not there)/ vac line to the ILC or the vac line to the vacuum tank from the anti diesel solenoid. I checked to see if the MCS clicked and it did. After that I fired up the engine. Cranked over twice, fired up and ran decent. A big improvement over how my uncle had to start it up, which is using starter fluid. Otherwise he said it wont stay running.

Now after all that I decided to slap the new carb on...I set everything on the carb as per the instructions with the rebuild kit. It didnt fire up right away so i had to pour some gasoline in the carb. After a few tries it fired up. Now heres were im a little freaked out. It idles insanely high for my taste, but theres no tach so i cant check. If i had to guess id say it was around 1600-2000 RPM. The idle screw on the driver side of the carb isnt touching the throttle linkage, so i figured i have to mess with the fast idle screw... I screwed it out a bit and it kicked down the RPM's a little, but still running fast. Another thing is that all of a sudden it seems like the air pump is blowing like a mad man unlike before... I mean i could clean the leaves of my lawn with the thing.

So i need some help... Im not sure what to do now. I dont wanna run the engine for too long and cause any damage seeing as im not sure what the heck is goin on. What should I do?

[dougbfresh]

Get a tach on it, my 1st guess would be a vacuum leak somewhere but who knows with this Frankenstein.

[ziolo]

It seems i got ahead of myself and freaked myself out, but what can i say... The autos program i went through had a crappy curriculum. Seems i jumped the gun and didnt take a close look initially. Seeing as the old carb didnt have the ILC and the new one did, that ended up being my issue. The ILC screw wasn't allowing the throttle linkage to drop, hence keeping the idle really high. So i removed it..Problem solved.

What should the RPM's be while its cold on the fast idle screw? What should the RPM's be once fully warmed up? Would i just set the fast idle, then wait for it to warm up then adjust the air/fuel screws as well as the curb idle screw?

Get a tach on it, my 1st guess would be a vacuum leak somewhere but who knows with this Frankenstein

. LOL. It really is a Frankenstein.