Fuel System: Carter AFB question

[David Daoust]

I had a newly-rebuilt Carter AFB carb installed (replacing an older Carter WCFB) on my 64 Daytona. Now, if I go a number of days (4 or more) without starting the car it becomes very difficult to start - to the point that I'd run the battery down if I didnt give the carb a shot of starter fluid. However, if the car had been started recently....it re-fires without issue.

I've heard different theories...."it has to do with modern gas evaporating faster"......"it is a known issue with Carter AFBs"....."the fuel is leaking out of the float bowl and perhaps even draining into the oil pan"

Has anyone else experienced these issues? Any advice on how to go forward?

Any help appreciated.

David Daoust
Stratham, NH

[karterfred88]

Well yes and no. Depends on temperature, the warmer it gets the worse it gets, but I have a glass bowl fuel filter to see the fuel pump flow and observe if it's full, 1/2 full or empty before trying to start. If I don't see fuel flow on the first or second start attempt, I remove the bonnet ( R2 engine) use an old fashioned oil can with fuel in it and squirt fuel into the float vents on the carb till I see fuel squirt from the accelerator pump into the primaries. Then try starting. It should run right away, then fill the glass bowl, if not I kill it. Saves the battery. I don't know if your fuel gets the summer/winter blending or not. But my fuel evaporates quickly from the float bowls, and will syphon gas into the carb from the filter as the floats drop. I don't have a solution other than what I do. I believe my fuel is very volatile here. It is not getting into the oil pan as it can only drip into the intake plenum or down the outside of the carb, so that theory doesn't work unless it is flooding and running very rich when it starts. Smell you're oil on the dipstick, if it smells like gas, check your fuel pump, not your carb, it can go into your pan from there, only way from the carb is if it is running super rich. I don't know if this problem is more pronounced on the AFB than the WCFB, my only experience is on my Avanti. It takes about a week to get to the point where I can see fuel moving in the glass bowl as I'm starting the engine and about a month till I see its almost empty. You might try checking you fuel pump diaphragm to see if it has not hardened up from alcohol and the check valve inside is working to keep fuel from running back to the tank, making it work too hard to refill the lines. If you are having a problem after 4 days, I would make sure I had a filter I could see into and observe the fuel flow, to see how long it takes to get fuel pushed to it and then to the carb bowls, and diagnose it from there.

[Mike Van Veghten]

NOT...a theory..!
Gas evaporates faster than in the past, fact of today's life. That's what electric fuel pumps are for.
There are no gaskets to leak below the fuel level on an AFB/Edelbrock carburetor. The fuel would not go into the pan right away anyway, it would take a little time to leak past the rings, depending on where the ring gaps are located on each piston.

Put a Carter inline pump back by the front leaf spring hanger. Quiet, effecient, and doesn't require a lot of electrical power to run it. The one on my 259 powered Lark works great.

Mike

[TWChamp]

I have the exact same problem on my 1950 Champion. Last winter I even took the carb into the house and left it for 3 days full of gas over an empty ice cram pail. No gas in the pail, and the carb was still full, so it has to be the engine heat evaporating the gas we have these days.

[SN-60]

I agree with above, but you should also check out the accelerator pump to make sure it's primed and working as it should. As well as the automatic choke adjustment.

[StudeRich]

You and others may be over-thinking this, usually all it takes to make a Carter WCFB or AFB 4 Barrel fire right up on the first or 2nd. turn is ENOUGH Choke!

When you gently depress the throttle 1/4 way down and release before cranking, three things happen:

#1 You get a spurt of Fuel in the primary throttle bores.

#2 You set the Automatic Choke.

#3 You set the fast Idle Cam.

Of course for #2 & #3 to Work, they must both be properly adjusted.

[TrickyRick]

And the choke plate should close completely then as soon as the vacuum comes up the choke pull off should pull the choke blade open to the specified opening.

A blip of the throttle should bring the idle down off the high step to the second step.

[Xcalibur]

I don't know how many "rebuilt" old carbs I've seen that had any number of issues, including missing pieces!!! If the carb really is correct it will work correctly, even on today's gas. I've replaced many old AFBs with a NEW carb and cured any number of supposed issues, carb-related and otherwise. All the best.

[63 R2 Hawk]

I have seen AFBs (Aluminum Four Barrel) ruined by "rebuilders" who like to bead blast them or soak them in solvents that strip the factory coating and cause them to become porous and create rough gasket mating surfaces. Capillary action allows fuel to flow through the tiny porosities and evaporate. Pretty and shiny is not always a good thing for cast aluminum.

[altair]

I would confirm that your fuel line has no pin holes. If the fuel is pumped to the carb bowl and the float and needle are shutting the fuel off the fuel should stay up to the fuel bowl in theory for ever. If there is a pin hole in the line the vacuum created by the fuel pump will bleed off and the fuel supply line will be replaced with air. Two simple tests first attach a section of clear fuel line to the carb and see if the fuel bleeds off, it shouldn't. If it does remove the fuel line and attach a long rubber hose and gently blow in to it (you don't need a compressor), just blow gently and spray the fuel line from the carb to the tank with soapy water, with particular attention at each clasp and look for telltale bubbles. During normal operations the fuel line is under vacuum and a leak will not show, only when it is shut off. The leak will evaporate and it will be unnoticed. I went through the same symptoms, three different carbs, three different fuel pumps, to start I had to prime each time. After I discovered the pin holes in the fuel line and replaced the entire system the car starts on the first or second turn even after sitting for days.

[bezhawk]

I would confirm that your fuel line has no pin holes. If the fuel is pumped to the carb bowl and the float and needle are shutting the fuel off the fuel should stay up to the fuel bowl in theory for ever. If there is a pin hole in the line the vacuum created by the fuel pump will bleed off and the fuel supply line will be replaced with air. Two simple tests first attach a section of clear fuel line to the carb and see if the fuel bleeds off, it shouldn't. If it does remove the fuel line and attach a long rubber hose and gently blow in to it (you don't need a compressor), just blow gently and spray the fuel line from the carb to the tank with soapy water, with particular attention at each clasp and look for telltale bubbles. During normal operations the fuel line is under vacuum and a leak will not show, only when it is shut off. The leak will evaporate and it will be unnoticed. I went through the same symptoms, three different carbs, three different fuel pumps, to start I had to prime each time. After I discovered the pin holes in the fuel line and replaced the entire system the car starts on the first or second turn even after sitting for days.

With fuel maybe 15 years ago, yes, I would agree. However, NOT with todays crap, it WILL evaporate under just normal operating temperatures. Todays fuel is not designed to be run in non pressurized fuel systems (carburetor or open to atmosphere pressures) . period. It WILL boil dry right before your eyes. Don't take my word for it, try using a glass see through filter, and watch it after a thoroughly warmed up engine is shut off. Watch it boil. The same thing is happening inside the carburetor.

[karterfred88]

With fuel maybe 15 years ago, yes, I would agree. However, NOT with todays crap, it WILL evaporate under just normal operating temperatures. Todays fuel is not designed to be run in non pressurized fuel systems (carburetor or open to atmosphere pressures) . period. It WILL boil dry right before your eyes. Don't take my word for it, try using a glass see through filter, and watch it after a thoroughly warmed up engine is shut off. Watch it boil. The same thing is happening inside the carburetor.

Agree, and worse yet if it has alcohol in it, it absorbs water vapor from the atmosphere. All that's left in you gas tank after 6 months of sitting is-----water--! Since there is no way of sealing a carb delivery system in our old cars, no way of keeping it under pressure as in new FI systems, we will continue to have these problems unless we all change over to FI and modern fuel systems--destroying the very thing we want to preserve. Or, we can lobby gas refiners to produce fuel we can use--yeah right--we represent a shrinking market, I forgot that little tidbit. We will have to find a way to cope to survive.

[altair]

Further to my comment, if the needle valve in the carb and the check valve in the fuel pump are both seating the fuel up to the carb bowl should not escape. It is the same principal as dipping a straw in liquid and holding your thumb over the top, the liquid will stay in the tube for ever. Obviously a pin hole in the tube will release the liquid and if the seal at the top is not tight will also release the liquid. I am not disputing that the fuel in the bowl may boil away (usually when the heat riser is stuck closed). If the fuel did boil out of the bowl, with the fuel line to the tank full of fuel, it should take no more then 10 revolutions to restore the fuel in the bowl. With one small pin hole it will never start with out priming.