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rochester q-jet!

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cerryblazer

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http://www.flickr.com/photos/91146104@N07/8278306156/
hi guys! i'm Fabio from North Italy and i have a 1981 blazer k5 with a carburetor problem
are you an expert of rochester quadrajet carb?!
i don't see the jets of gas go out into the venturi!
i replaced all parts with a repair kit but not good news.
i don't understand why, as the pic in the link, when i push down the accelerator pump, the fuel goes out from the holes indicates with "red arrows".
while the good position would be the holes with the yellow arrow, because the squirts of fuel would be exactly above the venturi holes and where i saw them last times!

i found my old carb, the original, i opened it and i saw that there were two or three different parts compared to the second carburetor.
the old one, has a small barrier with a small hole in the position indicates from the "blue arrow" and as you can see in the carburetor in the pic. the new one, not.
then, the old one, has a black plastic cap where there is the "red ring", while the new one not!
i tried the carburetor also with these parts, but it doesn't still run!
how can i see the jets of fuel in the venturi holes!?!?!
please help me!

thanks for attention!
Fabio
 
If the pump is pushing fuel into the carb and you are still not seeing fuel then I would check and see if the needle is hooked up to the float or improper float level.

The red circle is the APT, it allows adjustment of the metering rod depth into the jets for fine cruise tuning. If I recall the APT is about 2 and a half turns out from the factory.
 
thanks Babaganoosh for reply!
the float seems to work well. i tried to mount different seats, (you know, the piece of brass where there is the needle) but no improvement.
i have just 2or3 doubts.
with the carburetor disassembled, i don't understand why the gas comes out from two holes but when the carb is reassembled the fuel should come from two other holes (red and yellow arrows in the link that i posted).
also the APT that you told me is strange, because the APT screw in the old carburetor is more screwed than the new one, but i have never touched it!
are there some other things to check? if i don't see the jets what i must check?
you told me needle, float level (i followed the instruction and is 3.6" or 4.7 mm) something other!?
ehy thanks again for help!
Fabio
 
Those pieces should be there. With the carb assembled and the pump works
If fuel is coming out where you say and not at the venturies you have a blockage.
 
I'm not the most knowledgeable one on quadrajets but I couldn't get fuel to come out of the yellow arrows and it was the needle hooked onto the float. I'll attach a pic of what I mean.

Each carb APT will be adjusted differently depending on rebuilder, jets or rods used. I put my carb back to stock jets and rods from what the engine called for and played with the APT until I was completely happy. It felt like a fuel injected engine after I was done. :pimp: So smooth through the RPM range.

0900c15280083663.gif
 
Fuel goes up thru the gasket to the top airhorn and out the squirters.
Compare old with new gasket. Did you put the check ball back in?
Apt is another deal, leave it at 2.5 to 3 turns for now. These carbs are calibrated for each application.
 
thanks guys!
so...i replaced the original carb with new one 4-5 years ago, remanufactured, but actually i had problem with this last.
i replaced: ball, accelerator pump, needle, hook, float...in the right position
i cleaned everything. i didn't touch APT.
then i opened my last carb to check if i forgot some piece but all seems the same...
Fabio
 
Fuel out of red arrows good, from there not yellow arrows.
Goes straight up to top of carb and out small holes above venturies.
If not u have a blockage in airhorn or it's not put together correctly.
 
That's correct, you will see it in venturies but comes from above and into.
Both sides have their own passages after it leaves the pump.
The pump has an integral spring and one under it.

If fuel shoots out of red arrow holes with top of carb off It should be working with the top on into the venturies if the pump is providing good pressure.
 
now i have a doubt but i'm almost sure that the squirts of fuel that i saw, came out from what you call "upper main air bleeds".
because if i spray inside the holes with yellow arrows in the pic, the squirts come out from the two main jets closed by the two long metering rods.

http://www.flickr.com/photos/91146104@N07/8278306156/

but i don't understand the opposite direction...how can the fuel goes out from the main jets and climb up thye holes that you call "upper main air bleeds"??
i hope to be clear!
thanks
Fabio
 
cerryblazer said:
now i have a doubt but i'm almost sure that the squirts of fuel that i saw, came out from what you call "upper main air bleeds".
because if i spray inside the holes with yellow arrows in the pic, the squirts come out from the two main jets closed by the two long metering rods.

http://www.flickr.com/photos/91146104@N07/8278306156/

but i don't understand the opposite direction...how can the fuel goes out from the main jets and climb up thye holes that you call "upper main air bleeds"??
i hope to be clear!
thanks
Fabio
Click to expand...

Ok this pic of main body red arrows pump supply to airhorn and pump discharge. yellow arrows are your main feed, the main air bleeds in the airhorn sit above these holes. these are not for the pump. (yellow)

Vacuum pulls the fuel up from jets to climb the holes for main supply, hope that answers your question.

The pic of the airhorn red arrows are main air bleeds, blue arrows are pump feed from the main body of carb to the discharge in the airhorn not actually in the venturi itself.

From the pump goes past the check ball up the passages on both sides into the airhorn and out the pump discharge in the airhorn and sprays into the venturi area, if fuel is not doing this your pump is not working or you have a blockage, check your gasket again and make sure the holes are there for the pump supply from main body to airhorn,

See Pics I included for where the pump discharge is.

You need to get this book Rochester Quadrajet Carburetors by Cliff Ruggles,
He has a website www.cliffshighperformance.com He also has a great forum on just Quadrajets.

The last pic show the actual pump discharge in the airhorn.

Q1.jpg

Q2.jpg

Q3.jpg
 
ok! i understand. it's vacuum which pulls fuel from main jets!
so it only happens when the engine is running?
I remembered seeing the jets also with motor off, but probably i wrong.
so if all parts are ok , carburetor must work!
thanks again Blazer 74
Fabio
 
Correct. For the exception of the acc pump which only works when you move the throttle linkage. The pump is strictly mechanical. If the pump does not supply fuel when you move the throttle linkage you will not be able To start a cold or engine that has been sittng a while unless u pour a small amount of fuel down the venturies.

Hope this helps, Craig
 
thank you very much for your help Craig!
indeed my truck starts just if i put a small amount of fuel directly in the venturi holes.
i think i'll get another repair kit because i open and reopened 1.000 times my carburetor and it still has problems.

thanks again
Fabio
 
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