Cold start problems with rochester quadrajet. Fuel draining out of carb ? - Pontiac GTO Forum
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post #1 of 9 (permalink) Old 07-09-2011, 09:02 AM Thread Starter
 
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Cold start problems with rochester quadrajet. Fuel draining out of carb ?

I have a 1968 GTO 400 4-speed with the original 7028263 Rochester Quadrajet. It has a new fuel pump, new inline filter with a new return line to the gastank. The 1st start of the day takes lots of cranking but the engine finally fires up. The chocke works properly and high idles until warm. However, after it is warmed up and the choke fully open and when I turn off the car, it will not start again. I spray a little starter fluid and it starts instantly. However, it does not idle great and wants to stall. Driving down the road seems fine. I took the air cleaner off and with the car not running worked the throttle and did not see any fuel coming out. No stream, nothing. Its like the carb is instantly draining itself down when not running. I took off the gas line and looked at the carb filter, see photos. Is this supposed to be a check valve so the gas doesn't drain out of the carb? Any help would be appreciated. It's embarrasing having to carry around a can of starter fluid.
Thanks in advance.
Al Barlow





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post #2 of 9 (permalink) Old 07-09-2011, 04:43 PM
 
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Sounds like the accelerator pump in the carb is bad. They like to harden up over time and stop squirting. I would rebuild the carb with new gaskets and needle and seat. I would also pick up the metal float instead of using the plastic one that will be in the kit. With 3 cans of carb cleaner.

Those stone filters are not the best you can swap out the filter housing with a newer style filter and housing from a carb from the mid to late 70's. That have the paper filters inside. The paper ones will harden up like the acc pump from the ethanol in today's gas, but offer better filtering. I like to run the rebuildable clear filters from autozone inline on the rubber line. So I can see how well the gas is flowing and how dirty the filter is.

My old 350 chevy, I had in my 67 Camaro for a few years, had a very bad accelerator pump, and didn't squirt either. But the engine had enough vacuum to pull the gas from the carb. That is what is happening to yours. When the choke is closed it causes enough vacuum to pull fuel but when it opens up it no long can get gas.

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post #3 of 9 (permalink) Old 07-09-2011, 07:47 PM Thread Starter
 
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Thanks for the advice. I will order a rebuild kit tomorrow from NAPA.
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post #4 of 9 (permalink) Old 07-10-2011, 11:05 PM
 
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you can just use the short paper filter in the carb body, no need to change to another bowl nut. Paper filter comes with or without check valve. Your carb needs a rebuild, and probably has some linkage at the casting plugs and the well on the carb body. That will need to be sealed.
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post #5 of 9 (permalink) Old 07-11-2011, 09:27 AM
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IMO I'd stick with the internal ceramic fuel filter.. If you insist on a paper filter, I'd hide it down by the fuel pump. That whole set up up top IMO looks mickey mouse.

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post #6 of 9 (permalink) Old 07-15-2011, 05:04 PM Thread Starter
 
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OK so I have added a new fuel pump, replaced all of the gas line hose and rebuilt the carburetor twice just for good measure and here is what it does. Starts up pretty quick when cold and runs OK. Once the car is up to temp and the choke fully open, I shut it down. It will not start again. Add a shot of starter fluid or just wait about 15 minutes and it starts right up. When I removed the top of the carb and then pushed down on the plunger gas squirted up through the two holes. Why doesn't any gas squirt when I put the carb back together and install it? Please help, I am running out of starter fluid.




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post #7 of 9 (permalink) Old 07-15-2011, 05:56 PM
 
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You might try asking Cliff Ruggles about this. he posts frequently on the PY forum. He also wrote a book about Q-Jets......you'll get it going, don't worry!! Eric



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post #8 of 9 (permalink) Old 07-15-2011, 10:06 PM
 
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a hot start shouldnt require an accelerator pump or choke. i doubt the carb runs dry that fast. the fuel filter would not come into play. the fuel pump sould not come into play. are you sure its not flooding when you shut it off? shut it off hot and open the throttle all the way and look in there with a flashlight. there should be no liquid gas. thats the only thing that makes sense to me considering you said this: " I spray a little starter fluid and it starts instantly. However, it does not idle great and wants to stall."
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post #9 of 9 (permalink) Old 07-15-2011, 10:55 PM
 
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Quote:
Originally Posted by Eric Animal View Post
You might try asking Cliff Ruggles about this. he posts frequently on the PY forum. He also wrote a book about Q-Jets......you'll get it going, don't worry!! Eric


Before you pull the carb again buy Cliiff Ruggles book and read it before ripping into your carb. I would also buy the rebuild kit from Cliff. He uses material that is ment for oxygenated fuel (today's fuels). The kit from Napa is not ment for todays fuels. I have learned the hard way.
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