another carb issue
Thread Starter
Racer
Joined: Jul 2009
Posts: 336
Likes: 1
From: Asheville N.C.
another carb issue
I'm new so let's see how it goes. 79 L48 rochester carb original rebuilt, starts, idles and runs great, float set at .400, new needle and seat, new fuel pump, fuel lines heat wrapped, 1/2" phenolic spacer, and still after a good drive and heated up, after it sets for about 30 min. it's hard to start like it's flooded or out of fuel, oh the carb plugs have also been epoxied. Even bench tested for leaks before assymbly. Crazy crazy crazy:
Le Mans Master
Joined: Jan 2004
Posts: 7,412
Likes: 75
St. Jude Donor '14
Hmmm....Maybe carefully put a little fuel into the throat of the carb and seal it back up and try to start. That will tell you if it is a fuel issue. Will a non-functioning vacuum advance cause start up issues?
I'm not sure of your wording. Does the car run well until you turn it off, and then it won't restart? How long does it sit before it will start again? Can you smell raw fuel as you try to start it?
If it dies when it is hot and then will not start, that could be a catalytic converter. We need more CLEAR info.
I'm not sure of your wording. Does the car run well until you turn it off, and then it won't restart? How long does it sit before it will start again? Can you smell raw fuel as you try to start it?
If it dies when it is hot and then will not start, that could be a catalytic converter. We need more CLEAR info.
Le Mans Master
Joined: Jul 2006
Posts: 8,117
Likes: 104
From: charlotte north carolina
dirt and rust from an old fuel tank can get into the carb(right thru the filter) and prevent the float valve from closing completely. gas will drip into the engine and /or hit the throttle plate and run along the shaft and drip outside the carb and pool in a depression in the intake manifold(yes , i saw this with my own eyes for about one microsecond before i got a fire extinguisher). it will also appear that the carb is smoking as the gas evaporates. i dropped the sending unit, flushed the tank and line and also installed an in-line filter. i also noticed that the idle speed was creeping up(due to drip of extra gas) right before this near-fire.
Thread Starter
Racer
Joined: Jul 2009
Posts: 336
Likes: 1
From: Asheville N.C.
Hmmm....Maybe carefully put a little fuel into the throat of the carb and seal it back up and try to start. That will tell you if it is a fuel issue. Will a non-functioning vacuum advance cause start up issues?
I'm not sure of your wording. Does the car run well until you turn it off, and then it won't restart? How long does it sit before it will start again? Can you smell raw fuel as you try to start it?
If it dies when it is hot and then will not start, that could be a catalytic converter. We need more CLEAR info.
I'm not sure of your wording. Does the car run well until you turn it off, and then it won't restart? How long does it sit before it will start again? Can you smell raw fuel as you try to start it?
If it dies when it is hot and then will not start, that could be a catalytic converter. We need more CLEAR info.
Hello 7t5, the vacuum advance works fine, anytime I turn it off it will always hit the first time, it's only after it sets for at least 30 to 75 min. is when it's hard to start like flooded or out of fuel, so I hold the peddle down and crank and sometimes there will be fuel shooting out the top. The car needs to set for approx. 11/2 to 2 hours. Definetly can smell raw gas when restarting. The car never dies when hot or cold. Thanks so much for your input because this will need a greater mind than mine. ED79
Melting Slicks
Joined: Oct 2002
Posts: 2,317
Likes: 111
From: St Louis MO
Are you using the fuel return line? Without it, there is more residual pressure on the needle & seat after shutoff which can cause higher fuel levels in the carb and dripping into the manifold.
If you're using a larger diameter needle & seat (seat holes larger than .125"), many aftermarket fuel pumps have too much pressure for this larger seat and will overpower the Q-jet's float system, resulting in flooding.
If you're using a larger diameter needle & seat (seat holes larger than .125"), many aftermarket fuel pumps have too much pressure for this larger seat and will overpower the Q-jet's float system, resulting in flooding.
Thread Starter
Racer
Joined: Jul 2009
Posts: 336
Likes: 1
From: Asheville N.C.
Sensei, I did a vacuum check on the hose that tees from the pcv and the throttle body and goes to the canister, it held this vacuum until the idle speed came up to about 1500 rpm and then the vacuum went away so I'm just guessing it works. Did replace the short rubber between the vapor line return and canister. What or how to see if all parts of the canister are working, could the filter be the reason because I have not taken it out yet to replace. It just sounds like you can hear fuel dripping inside the front bowls, even after a cold start and turn it back off. Thank you for your help and concern,ED79
Thread Starter
Racer
Joined: Jul 2009
Posts: 336
Likes: 1
From: Asheville N.C.
Are you using the fuel return line? Without it, there is more residual pressure on the needle & seat after shutoff which can cause higher fuel levels in the carb and dripping into the manifold.
If you're using a larger diameter needle & seat (seat holes larger than .125"), many aftermarket fuel pumps have too much pressure for this larger seat and will overpower the Q-jet's float system, resulting in flooding.
If you're using a larger diameter needle & seat (seat holes larger than .125"), many aftermarket fuel pumps have too much pressure for this larger seat and will overpower the Q-jet's float system, resulting in flooding.
larrywalk, yes on the return fuel line, keeping everything close original, as for the seat holes I don't know what size it is, huh whatever came in the kit---how can I tell?????thanks ED79
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Thread Starter
Racer
Joined: Jul 2009
Posts: 336
Likes: 1
From: Asheville N.C.
dirt and rust from an old fuel tank can get into the carb(right thru the filter) and prevent the float valve from closing completely. gas will drip into the engine and /or hit the throttle plate and run along the shaft and drip outside the carb and pool in a depression in the intake manifold(yes , i saw this with my own eyes for about one microsecond before i got a fire extinguisher). it will also appear that the carb is smoking as the gas evaporates. i dropped the sending unit, flushed the tank and line and also installed an in-line filter. i also noticed that the idle speed was creeping up(due to drip of extra gas) right before this near-fire.
Melting Slicks
Joined: Oct 2002
Posts: 2,317
Likes: 111
From: St Louis MO
Also, the fuel pump is easy to check... A stock pump has two hose nipples underneath - one is 3/8 and has the rubber inlet "S" hose on it; the other is 1/4" and returns fuel to the tank through an internal orifice of .058" feeding the fuel return line. The third boss underneath takes an inverted flare fitting for the steel output line to the carb.