Carb Loading Up? (Cliff Built Q-Jet)

[grivera]

Lately, I've been experiencing an idle problem when placing the car in gear. Once the car is warmed up, if I place it in gear, it will idle poorly and then will turn off. Most of the time it is difficult to restart and the smell of raw fuel is evident from the exhaust when the engine is at idle. Once the engine cools some, it will start up with some coercion.

yesterday, I was at a local cruise and as I put it in reverse to back into a space, it turned off and wouldn't restart. Once it cooled, I was able to start it and fella there listened to the engine with me. He said the carb sounded like it was "loading-up." He explained that the needle is coming off the seat and too much fuel is getting past. On the way home, whenever I stopped at a light, I depressed the gas pedal slightly (with foot on the brake) to keep RPM's higher and prevent stalling.  Idle is set to about 850.

It drives great at any other speed besides idle, which isn't as smooth as it should be even while in park. What is going on with the carb and how do I properly diagnose it/fix it. FWIW, I'm not well versed in carbs.

Will R.

Vehicle Specs:

'69 Firebird
YT 400 (.040 over) stock deck height
Speed Pro Forged-9 cc dish ~9.4 comp
#62 heads @ 75cc/XE268 degreed in @ 105* ICL
Iron Intake/Cliff Carb/Airtex Fuel Pump
Dave's Small Body HEI
TH400 w/Hughes GM20 Converter
8.5 10-bolt 3.08 posi
LB Manifolds/2.5" exhaust/X-Pipe/Dynomax ST's

[grivera]

I forgot to indicate the carb number:


There are two numbers on it:

17058241
2307 BLT

Lately, I've been experiencing an idle problem when placing the car in gear. Once the car is warmed up, if I place it in gear, it will idle poorly and then will turn off. Most of the time it is difficult to restart and the smell of raw fuel is evident from the exhaust when the engine is at idle. Once the engine cools some, it will start up with some coercion.

yesterday, I was at a local cruise and as I put it in reverse to back into a space, it turned off and wouldn't restart. Once it cooled, I was able to start it and fella there listened to the engine with me. He said the carb sounded like it was "loading-up." He explained that the needle is coming off the seat and too much fuel is getting past. On the way home, whenever I stopped at a light, I depressed the gas pedal slightly (with foot on the brake) to keep RPM's higher and prevent stalling.  Idle is set to about 850.

It drives great at any other speed besides idle, which isn't as smooth as it should be even while in park. What is going on with the carb and how do I properly diagnose it/fix it. FWIW, I'm not well versed in carbs.

Will R.

Vehicle Specs:

'69 Firebird
YT 400 (.040 over) stock deck height
Speed Pro Forged-9 cc dish ~9.4 comp
#62 heads @ 75cc/XE268 degreed in @ 105* ICL
Iron Intake/Cliff Carb/Airtex Fuel Pump
Dave's Small Body HEI
TH400 w/Hughes GM20 Converter
8.5 10-bolt 3.08 posi
LB Manifolds/2.5" exhaust/X-Pipe/Dynomax ST's

[429bbf]

i dont know anything about airtex fuel pumps  but it sounds like you may have to much fuel pressure. have you checked it with a gauge? quads dont like more than about 7psi any more likes to unseat the needle and flood. hope this helps

[von]

I've had two new Airtex pumps on my stock 350 Chevy and they both put out 8-9 psi at idle measured at the carb.  My carb was flooding after the engine was shut off. I installed an AC Delco pump with 5 psi and problem fixed.

[Cliff Ruggles]

How many years has it been since we rebuilt the carburetor?

I'd replace the float, needle/seat assembly, accl pump and new top gasket.  Might want to check the bottom plugs as well, to make sure they aren't leaking.

We've got a few units back that have been out there quite a while with leaking bottom plugs.  This new fuel is pretty hard on the castings, at least it finds it's way past the bottom plugs easier than the older stuff.....Cliff

[grivera]

How many years has it been since we rebuilt the carburetor?

I'd replace the float, needle/seat assembly, accl pump and new top gasket.  Might want to check the bottom plugs as well, to make sure they aren't leaking.

We've got a few units back that have been out there quite a while with leaking bottom plugs.  This new fuel is pretty hard on the castings, at least it finds it's way past the bottom plugs easier than the older stuff.....Cliff

You sent it to me in '06, but it's only been in service since '09. Where are the bottom plugs located and how do I test/fix them? Any pictures on this site for reference? I know I can check your book, but it's on loan to my brother in NJ so I can't look at it for a few days.

I have a hard line to the carb from the pump and don't know how to check the fuel pressure with this configuration?

Is the AC Delco pump the basic replacement pump (#40679) as seen below?
http://www.amazon.com/gp/product/B000C9KT28/ref=ox_sc_act_title_1?ie=UTF8&psc=1&smid=ATVPDKIKX0DER

[grivera]

By the way, the carb has about 1500 miles on it since 2009.

[Ethan1]

I've had two new Airtex pumps on my stock 350 Chevy and they both put out 8-9 psi at idle measured at the carb.  My carb was flooding after the engine was shut off. I installed an AC Delco pump with 5 psi and problem fixed.

 Same here, Von. The Airtex I had ran it too high for the Qjet I had on my 406.

[grivera]

You sent it to me in '06, but it's only been in service since '09. Where are the bottom plugs located and how do I test/fix them?

Cliff, It probably has 1500 miles on it since. Are the bottom plugs still a possible source of the leak?

[Frank400]

Are you running with the original fuel return line ?  I've noticed it makes a huge difference in some cases.

[grivera]

Yes- metal 3/8" from tank to carb with the factory 1/4" return line.