More quadrajet help please! Won’t run

[Itali83]

Hey guys. Really bummed out after spending three hours trying to get my new truck going with no luck.

stock 350 with what appears to be a stock original quadrajet. I bought the truck and was able to hear it fire and run briefly by me pouring gas down the carb. Truck has been sitting 20+ years.

I took carb apart and found full of rust, float literally came apart and secondaries were pretty much seized. I totally took apart, soaked in carb cleaner and got everything like new clean and free.

Got a rebuild kit from quadrajetpower.com and put it all back together. I did drill out the plugs for idle air adjustment. Also punched out plug for part throttle mixture screw as well in hopes of being able to adjust without major disassembly every time.

I bottomed out the idle adjustment screws and backed out 2 turns to make them even and that seemed like a good baseline. Also backed out part throttle mixture screw 3 turns from what I found doing research.

the motor has good compression, good spark, clean plugs and good clean fuel and fuel pump. I can’t get the damn thing to run. It will fire but never catch. I’ve tried manually opening and closing the choke while cranking with little change. Sometimes it fires with choke open. Sometimes it needs choke closed and several pumps of the throttle. I can’t even get it consistent enough to figure out if I’m flooding it or too lean. Any of you guys have a tried and true set up to at least get the thing to run and then tweak from there?

this is my first q-jet. I’m a master diesel mechanic so I’m taking this a bit personal and a bit embarrassed I can’t even get this thing to run. I’m surely missing something simple. I also originally had the float too high and had fuel just pouring out of everywhere after the pump picked up fuel. I took the top off and bent the new float a bit to just eyeball fuel level and at least don’t have fuel overflowing but I know I have enough fuel in the bowl to at least start and run.

any ideas and help would be great.
Thanks!


Ben

 

[Itali83]

Forgot to add. I did seal up all the well plugs with jb weld. I had all vacuum ports plugged except the pcv and vacuum brake line.

I’m going to plug both of those lines because I didn’t test them and maybe they are bad and causing a major vacuum leak.

Ben.

 

[Octane]

If the filter is good and there is fuel pressure and good volume of gas coming thru it should fire up.Unless there is a blockage in the carb somewhere.Did you also blast it out with compressed air? Maybe turn fuel mixture screws out 2.75 turns.Its possible the carb is too corroded to get it cleaned out properly? I rebuilt mine recently, after over 40 years it runs great

 

[Ricko1966]

Take a dish soap bottle full of gas fill the carburetor thru the vent tube in the air horn. I don't know year so this part may not apply pull the big charcoal vent tube at the right side top of the carburetor off. Fill until fuel dribbles out of that port. Now start it. Does it run until the float bowl empties?

 

[Itali83]

After rebuild and install. I do fill float bowl with fuel. It fired first try but died almost instantly. Not like I shut the ignition off, but like bad mixture. This is 110% carb issue. Ignition is good.

the carb cleaned up real nicely and wasn’t very corroded. It was just full of rust and trash. Everything got removed and blown through. There are no blocked passages for sure. I’m going to plug the last two vacuum
Ports to rule out and source of vacuum
Leaks and try it again. I also got the choke coil cleaned up and installed so the choke should work properly by itself now too.

Here’s pictures of the carb cleaned up. It’s not corroded. Also, the throttle shafts are nice and tight. So this truck seems like a low mileage unit. Just been sitting for a while.

thanks
Ben

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[bedwards]

Have you checked the timing? Have the plug wires been off? If I remember right, #1 and #8 are easy to mix up.

 

[Ricko1966]

Are you 100 percent positive the float bowl is full?

 

[Ricko1966]

Wow just went back and read you need to hook up the pcv and brake booster. Those are massive vacuum leaks

 

[Itali83]

Wow just went back and read you need to hook up the pcv and brake booster. Those are massive vacuum leaks

they were hooked up. I just want to plug the ports instead of having them hooked up INCASE the pcv itself is bad or the brake booster is blown. I would never try to run anything with vacuum ports open.

 

[Itali83]

Are you 100 percent positive the float bowl is full?

110% sure bowl is full. Accelerator pump is shooting fuel when depressed

 

[Itali83]

Have you checked the timing? Have the plug wires been off? If I remember right, #1 and #8 are easy to mix up.

I’m going to check base timing to make sure but have verified firing order and it’s correct.

Ben

 

[bedwards]

good reading here:
https://www.google.com/books/editio...DwUMAaiyMoYC?hl=en&gbpv=1&printsec=frontcover

and here:
http://www.northstarchevelles.com/NonSecure/Tech/Carbs/QJet_Tuning_Paper.pdf

 

[Ricko1966]

Will it start and run on fuel directly down the throat of the carb?

 

[Itali83]

Will it start and run on fuel directly down the throat of the carb?

yes but only momentarily as I was by myself so I wasn’t able to feed it fuel while cranking. I’m going to make a under hood starter switch so I can crank while under the hood.

 

[Itali83]

good reading here:
https://www.google.com/books/editio...DwUMAaiyMoYC?hl=en&gbpv=1&printsec=frontcover

and here:
http://www.northstarchevelles.com/NonSecure/Tech/Carbs/QJet_Tuning_Paper.pdf

thanks. I got the Holley books when I got my first Holley and should get this or something similar now with this q-jet. Just figured I could at least get it to run and play with it from there. Gonna try a few things tomorrow hopefully and see how it goes.

Ben