Quadrajet help on volvo-penta..

[mopower440]

I have a 1986 bayliner capri with the 305 chevy engine (AQ225E) and 275 outdrive. I have rebuilt the thermoquad carb and she runs good, BUT, it does not respond to adjusting the mixture screws. I can turn them both all the way in, all the way out, or anywhere in between and it doesnt change anything. So im thinking the idle speed screw is up to high, but i can only back it out so far before the engine is just barely running..Then i did some research and came across a thread saying that most marine carbs dont have the idle air bypass feature, would this be true on partticular carb? This is the thread i saw it on, read post #4
Quadrajet Idle Mixture Adjustment - Chevelle Tech

 

[jerryjerry05]

Re: Quadrajet help on volvo-penta..

Not sure this will help??
Make sure the plugs are clean or new.
Plugs with carbon won't respond to the fine tuning.

 

[alldodge]

Re: Quadrajet help on volvo-penta..

I have a 1986 bayliner capri with the 305 chevy engine (AQ225E) and 275 outdrive. I have rebuilt the thermoquad carb and she runs good, BUT, it does not respond to adjusting the mixture screws. I can turn them both all the way in, all the way out, or anywhere in between and it doesnt change anything. So im thinking the idle speed screw is up to high, but i can only back it out so far before the engine is just barely running..Then i did some research and came across a thread saying that most marine carbs dont have the idle air bypass feature, would this be true on partticular carb? This is the thread i saw it on, read post #4
Quadrajet Idle Mixture Adjustment - Chevelle Tech

All carbs marine and auto have idle circuits which are used when the air flow passing the throttle plates causes the venturi's to suck fuel in. The idle screws adjust the amount of fuel being allowed in. If your idle screws have no effect (and you said they do not) your carb needs to be cleaned better this time. When you tried to clean it the idle ports remained clogged. Cleaning the crud out of the idle ports is difficult and depending on how much is clogging up the really small ports you may be better off getting another.

 

[Maclin]

Re: Quadrajet help on volvo-penta..

Being a MoPar fan right from my DNA I appreciated this "Freudian" slip "...I have rebuilt the thermoquad carb..."



Back to regularly scheduled programming...

 

[mopower440]

Re: Quadrajet help on volvo-penta..

Woops, I meant quadrajet..lol..I've built so many thermoquads in my day I have them stuck in my brain..lol anyways, all circuits are clean, I promiss that..

 

[alldodge]

Re: Quadrajet help on volvo-penta..

Woops, I meant quadrajet..lol..I've built so many thermoquads in my day I have them stuck in my brain..lol anyways, all circuits are clean, I promiss that..[/QUOTE]

Sorry buy, the only thing left is you need to replace the carb

 

[Silvertip]

Re: Quadrajet help on volvo-penta..

If the idle SPEED is set too high, and the idle MIXTURE screws are turned all the way in, of course the engine will die when you back the idle SPEED down. This entire process is a balancing act. Idle speed, idle mixture, idle speed idle mixture, etc. You make idle SPEED adjustments downward just to the point where the engine stays running. Then adjust the MIXTURE. RPM will likely rise again. Lower the idle SPEED again and adjust the MIXTURE. Repeat this process as many times as necessary. If you still can't get the idle SPEED down where it needs to be then the carb has issues or there is a vacuum leak. Are the secondary air valves fully closed while you are doing these adjustments? If not they should be. If you had any of the air valve stuff apart, you likely didn't get the tiny spring and its adjustment correct either.

 

[jimmbo]

Re: Quadrajet help on volvo-penta..

Why did you rebuild the carb? How was it running before the rebuild?

 

[mopower440]

Re: Quadrajet help on volvo-penta..

Got it right finally! The reason the idle was set so high was the timing was set to 8 degrees AFTER TDC instead of 8 degrees BEFORE TDC like its supposed to be. so after setting the timing correctly i could turn the idle down enough to where the mixture screws respond. Got them tune to the highest vacuum and now she fires right up!

 

[jimmbo]

Re: Quadrajet help on volvo-penta..

Glad you didn't run out and buy a new carb