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quadrajet: the fuel pump, fuel bowl, and accelerator pump

Still seems like a lot of fuel lost to vaporization/evaporation. I'd be inclined to put an open container of gas out and see what it looks like after the same amount of time.

I'd be inclined to check the fuel level after the engine cooled off, see if a large amount of fuel is already gone since we know the carb and fuel get hot.
 
In the first 2-hours half evaporated.

Somewhere in this thread I posted an evaporation equation (I posted the link to where I found it) for fuel. Based on my underhood temperature and the humidity, I should expect a quarter to evaporate in the first 2-hours, and another quarter to evaporate over the next 24-hours. That is what I am finding with my modified 'chopstick' scale.

Apparently the ethanol evaporates like crazy.
 
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The choke is installed with an electric conversion, and the choke housing hot air port is plugged. I think the fuel bowl is empty at first. My fast idle is set low. I use my foot to warm it up and then I can drive around without the fast idle bothering me too much. My wife is doing the startup in the video, so she just starts it and then it is idling at maybe 500rpm - once warm and off fast-idle it idles at 550~650rpm.

It takes forever to come off fast idle. Earlier, I tried a hot choke setting so the idle would drop sooner, but the choke plate is open too far at cold so it is hard to start. I set it back to a colder setting but even then, the choke plate looks like it is open to much. Right now it is hard to start because A) the fuel bowl is empty, or B) the choke is open too far, or C) both the fuel is empty and the choke is open too far. I don't want to mess with bending the choke rod to adjust the plate until I know the hard start is due to the choke opening and not that there just isn't any fuel. I need to test for both.

I borrowed this mage from repairguide.autozone.com

0900c1528007fc8d.gif

Here is a link to fast idle adjustment on youtube by WhoSaidTyler https://www.youtube.com/watch?v=yX_hCujFQ_I
Another youtube here by TheYoshiClan on fast idle won't kickdown https://www.youtube.com/watch?v=XY_U5n52Oec

Here is my K5 startup from cold - I think it was sitting for five days before this.
[youtube]https://youtu.be/3mkL-wpzTyg[/youtube]
https://youtu.be/3mkL-wpzTyg

My best guess was that I had the electric choke connected to the old distributor 10v source - so it was slow to open. I checked and it has 12.5v. I still like the idea given in an earlier post to connect to the hot lead to the alternator - later I will give that a try.

After this video, I sprayed some WD-40 behind the choke housing, the movement of the weight seemed stiff. I think it helped allow the choke to open. The next step are A) check for fuel and B) cover choke w/ hand and see if it starts better. If B, then bend the choke rod. If A, I don't know.

The attached picture is idle at warmup. It is about 160 deg F and idling at 800rpm.

If you have any advice and just know what the problem is based on what I have posted here - I appreciate it if you share your knowledge so I don't have to go try the 'how bout this, bout that' game.

20150307_084151.jpg
 
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Fuel bowl empty cranking and pumping less than 10 seconds bowl is full and should fire if choke is set correctly.

The picture you have is the initial choke rod setting and is the only time you need to bend the choke rod, so don't bend anything. Get the proper procedure and verify that it's set correctly if you think its not. 1/8 drill bit IIRC for the adjustment under the choke.

Must have 12 volts to the choke.

The only thing that determines how long the choke stays on (fast idle) is how tight you wind up the choke spring. Turn the choke until it just closes the choke blade and use that as a starting point. If it opens to quick tighten more.

Next is your vac break diaphram. With vac applied to diapram should open choke blade 1/8 to 3/16 then adjust with the srew at the top of the diapram so the engine will not stall when first started cold, especially when placed in gear.

You need the proper procedure in front of you and read it till you understand it.

Your also missing the secondary rod from the diaphragm to the upper 2ndary flaps, that will create other issues.
 
Also turn in the fast idle screw till you have approx 1000 to 1200 rpm cold start which Wii be approx 1600 to 1800 warmed up. You must have enough fast idle to overcome cold friction of the engine to keep it running till it warms up. Choke setting and fast idle screw work in unison.
 
Blazer74 thank you.

I temporarily removed the secondary rod as a test. There is a thread in one of the forums with a debate about the funtion of the dashpot moderating the secondary opening. I want to know what both posters are saying to I pulled mine off. I never get into the secondaries so it does not affect everyday driving. I will save my opinions on the secondary rod for another thread.

I will turn up my fast idle speed and post the results.
 
Remove the gasket and plug the small hole. I fill the hole on the carb body with epoxy before I install the choke housing, you can also fill the little plastic adapter between the choke housing and carb body or last fill the hole under the choke spring in the choke housing so as not to have to take the choke apart for now.





Only thing your going to gain from removing the 2nd rod is a bog when 2nd open.
 
Well yes, that is the argument about the secondary rod. I looked for the thread to post a link and I cannot find it, a corvette forum is what I remember.

I wanted to see the claimed bog poster A claimed and the throttle response claimed by poster B. I see what they say. If I just mash on the pedal drag style then yes it has a huge bog. Could be because I have not tuned my secondary air valve tension. If I ease on and off the gas at rpm, more of a road race style, then there is no bog, but there is this crisp response. I only had the chance to give it one try. I think it would take time to get a feel for where the bog is and stay out of it. Overall, I am putting the secondary rod back in. I understand what the two posters were referring to, something I think they themselves did not do.
 
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I increased the fast idle to 1,000rpm cold (1,400 warm) and adjusted the choke plate for less plate gap.

The result: This morning it took three tries to start. It has been idling awhile and the fast idle is still engaged. The engine temp is now 170 deg F. It is basically stuck on fast idle.

Next:

I removed the gasket from the choke. I never looked too close but on one of the threads it said that the gasket should stay and that the housing has a tab to transfer the ground.

I started back and after a short time the fast idle disengaged. I will give a followup on if this fixed the fast idle sticking. Later I will see if I can adjust the choke to fix the hard starting.

20150323_084017.jpg

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The problem with these carbs is that there are SO many variations and components that getting everything to work together can be a real pain once things start going wrong. They are great carbs, just more complex than most people will spend the time to get right.

Realistically, this is why folks go with fuel injection. It is insanity to try and get a carb to work like a modern vehicle. Different back in the day when there were no options and everything was fairly new. ~30 years later, it's a lot of pain.

I'd say choke is probably the hardest thing to set on these carbs. I know I liked the electric choke on mine, it was consistent.

For the secondaries, you can actually "tune" the vacuum breaks by increasing the diameter of the hole in them, so they bleed vacuum off faster. The faster the vacuum bleeds off, the faster the secondaries are allowed to come in, without "flutter". Unfortunately when you go too far, the breaks garbage. Maybe some epoxy could be used to start over.

It takes almost no throttle to be into the secondaries. Most people THINK they aren't into the secondaries, when in actuality they are constantly used. I always thought it would be interesting to wire the secondaries shut to get a feel for what it is really like when they don't work.

A vacuum gauge is an interesting thing to watch while driving.
 
"just more complex than most people will spend the time to get right."

I am known for sticking with things until I get it, there are no unfinished projects around my house

8 months and counting on getting this q-jet right.

I think I spent 8 hours total on my holley in 20 years

(EDIT: 12 months and still messing with the q-jet)
 
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The issue most people have with them is not understanding how everything is interrelated. I don't think you have that problem, perserverance will get you through this, but as with the choke, any adjustment to one component on it, will affect other operations. Understanding what does what, and how one operation impacts another, is what gets to the bottom of these problems.
 
dyeager535 said:
For the secondaries, you can actually "tune" the vacuum breaks by increasing the diameter of the hole in them, so they bleed vacuum off faster. The faster the vacuum bleeds off, the faster the secondaries are allowed to come in, without "flutter". Unfortunately when you go too far, the breaks garbage. Maybe some epoxy could be used to start over.

It takes almost no throttle to be into the secondaries. Most people THINK they aren't into the secondaries, when in actuality they are constantly used.
Click to expand...

You are right about the secondaries. I cant justify taking too much time on secondaries tune. I will buy a couple vacuum breaks and drill them out. I will start or add to a new thread dedicated to the secondaries. Most likely I will see the the tune results in gas mileage, consistent 13mpg.
 
Secondaries are fun to play with when talking the tuning of the air valve spring alone, but outside of that it gets fairly complicated.
 
After starting up this morning.

This afternoon it started rightup, like it used to. The fast idle went for awhile so I went ahead and started driving. About half way (maybe 5 blocks away) to my daughter's shool the fast idle kicked down. Nice. The clutch was less finicky when cold with the fast idle - so that might be better for my wife.

Leaving her school it did not start right up, I had to hold the gas a bit and then it idled real low for a few seconds, almost died. I am guesing the choke was still hot and had not closed. At least the fast idle didnt reingage.

Next:
-Turn fast idle down from 1500rpm to 1300rpm warm (800 cold).
-Choke seems ok as long as it continues to fire that nice when cold.
-Figure out hot stop and restart short time later, how does that work? Choke is open no matter what?
-Retune idle mixture, maybe after filing the body I can get rid of that 'leaning' hose workaround for plugged ports.
-Still wont start after sitting for a few days, where's my fuel?
 
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Seriously mucking with this could be easily resolved with an electric pump and return line.. :Facepalm:
 
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