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Lot's of AFB people report the carb is dry after the car sits idle after a couple of weeks.
I believe the problem is today's gasoline evaporating away after shutdown. I don't recall this being a problem back when I drove AFB's daily but I never had the engine shut off long enough to hardly get cold.
If you want to try it, you can buy a cheap valve with hose nipples for a few bucks and install it inline before the fuel pump. I don't think it will fix your concern but you could try it.
Put an electric pump on the car if it bothers you too much.
Lot's of AFB people report the carb is dry after the car sits idle after a couple of weeks.
I believe the problem is today's gasoline evaporating away after shutdown. I don't recall this being a problem back when I drove AFB's daily but I never had the engine shut off long enough to hardly get cold.
If you want to try it, you can buy a cheap valve with hose nipples for a few bucks and install it inline before the fuel pump. I don't think it will fix your concern but you could try it.
Put an electric pump on the car if it bothers you too much.
AFB's on one Dodge I had and two GTO's I had would go dry in about a week from evaporation. This was 20+ years ago with GOOD gas. My Q-Jet is about the same due to small float bowl size. My 2-Jets in the '65 take longer to evaporate out: bigger bowls by far. The Model T never has an issue: the float bowl is lower than the fuel tank, and it's a gravity feed system. Always has fuel as long as the tank has fuel in it. The O.P. doesn't have an issue: Not a fuel pump, not a carburetor, not a check valve. He is experiencing evaporation in action. It will be interesting to see him replace a bunch of parts and still have the same issue...evaporation.
AFB's on one Dodge I had and two GTO's I had would go dry in about a week from evaporation. This was 20+ years ago with GOOD gas. My Q-Jet is about the same due to small float bowl size. My 2-Jets in the '65 take longer to evaporate out: bigger bowls by far. The Model T never has an issue: the float bowl is lower than the fuel tank, and it's a gravity feed system. Always has fuel as long as the tank has fuel in it. The O.P. doesn't have an issue: Not a fuel pump, not a carburetor, not a check valve. He is experiencing evaporation in action. It will be interesting to see him replace a bunch of parts and still have the same issue...evaporation.
It would be interesting to see if the bowls are actually empty from evaporation. It seems as if the portion of gas that promotes rapid combustion is gone, leaving the rest to be pumped through the system before fresh gas finally reaches the cylinders.
It would be interesting to see if the bowls are actually empty from evaporation. It seems as if the portion of gas that promotes rapid combustion is gone, leaving the rest to be pumped through the system before fresh gas finally reaches the cylinders.
Very possible but later AFBs (and Edelbocks) use a V-notch in the upper wall of the accelerator pump well to feed the pump from the driver side fuel bowl. So even if there is some fuel left in the bowl it's not high enough to fill the accelerator pump until the fuel pump fills it up and the idle circuit doesn't introduce enough (if any) fuel alone, to fire the engine.
I think earlier AFBs feed the accelerator pump from a passage fed from a lower point in the bowl so they may not have been as susceptible to having a dry pump well after sitting for a week or more. That plus the much less-volatile fuel back then.
[QUOTE=Frankie the Fink;1597395526]Look, I've overhauled 10-12 carbs in the past decade, I put them on the car bone dry, bowls empty, fuel filter empty. It takes 5-7 seconds for the car to start and idle, on a very few rare occasions it might take two tries...not usually. if you have the time to comment to a 70 year old who is still trying to learn, how do i check fuel pump flow? any special tools? my fuel pump may be the guilty one. something is allowing the fuel to drain back towards the tank. i have to unhook the fuel line at one of the carbs and crank again for a few seconds before i see any fuel coming out. or, the other view is the fuel is evaporating after sitting for a couple of weeks. being disabled sometimes creates these situations.
thanks,phil
After my 67 has set for a while the fuel bowls on the Holley are pretty much empty. I like to crank it in two sessions of maybe 5 - 7 seconds each until the oil pressure comes up above 30 psi.
By then the fuel bowls are full again and, with 2 or 3 pumps of the gas pedal (no choke on this one) the car fires right up.
You can re fill the float bowl thru the vent with the air cleaner off also
If you take the pump-to-carb line off at the carb with the ignition coil grounded and put the line into a clear mason jar and crank the starter you should get a healthy flow of gas of at least several ounces in 7-10 seconds.
Your fuel is not "draining back", most likely evaporating.....there is no "check valve" in the fuel pump beyond the poppet valves...and those are for fuel inlet/outlet respectively...components 4 and 5 below.
Last edited by Frankie the Fink; Jun 15, 2018 at 07:37 AM.
If you take the pump-to-carb line off at the carb with the ignition coil grounded and put the line into a clear mason jar and crank the starter you should get a healthy flow of gas of at least several ounces in 7-10 seconds.
Your fuel is not "draining back", most likely evaporating.....there is no "check valve" in the fuel pump beyond the poppet valves...and those are for fuel inlet/outlet respectively...components 4 and 5 below.
Look, I've overhauled 10-12 carbs in the past decade, I put them on the car bone dry, bowls empty, fuel filter empty. It takes 5-7 seconds for the car to start and idle, on a very few rare occasions it might take two tries...not usually. if you have the time to comment to a 70 year old who is still trying to learn, how do i check fuel pump flow? any special tools? my fuel pump may be the guilty one. something is allowing the fuel to drain back towards the tank. i have to unhook the fuel line at one of the carbs and crank again for a few seconds before i see any fuel coming out. or, the other view is the fuel is evaporating after sitting for a couple of weeks. being disabled sometimes creates these situations.
thanks,phil
Hi Phil, what most of us are saying after years and years of owning these cars, some of us for 4-6 decades.....know that our carbs...allow the fuel to evaporate, drain back, disappear....what ever you want to call it....
It usually takes a few spins of the engine to get fuel back into the bowl after sitting for a day, a week , a month....
We all learn the best way to get the car started....everyone has their own technique .....lol.....
Hi Phil, what most of us are saying after years and years of owning these cars, some of us for 4-6 decades.....know that our carbs...allow the fuel to evaporate, drain back, disappear....what ever you want to call it....
It usually takes a few spins of the engine to get fuel back into the bowl after sitting for a day, a week , a month....
We all learn the best way to get the car started....everyone has their own technique .....lol.....
Jack
Modern fuel injected cars with electric hi-pressure fuel pumps have us spoiled....methinks...
If you take the pump-to-carb line off at the carb with the ignition coil grounded and put the line into a clear mason jar and crank the starter you should get a healthy flow of gas of at least several ounces in 7-10 seconds.
Your fuel is not "draining back", most likely evaporating.....there is no "check valve" in the fuel pump beyond the poppet valves...and those are for fuel inlet/outlet respectively...components 4 and 5 below.
thank you for the advice. i wonder why every auto aftermarket company in the country makes in line check valves to prevent drain back? i guess it's just something i don't fully understand.
Hi Phil, what most of us are saying after years and years of owning these cars, some of us for 4-6 decades.....know that our carbs...allow the fuel to evaporate, drain back, disappear....what ever you want to call it....
It usually takes a few spins of the engine to get fuel back into the bowl after sitting for a day, a week , a month....
We all learn the best way to get the car started....everyone has their own technique .....lol.....
Jack
thanks for the reply. my main concern is it takes 6 or 7 sessions cranking with no result. then i have to take a line lose and crank again to get fuel at carbs. seems like a glitch.
phil
You can re fill the float bowl thru the vent with the air cleaner off also
thanks for your reply. my concern is that it takes 6 or 7 sessions cranking and then i have to take a fuel line off at the carb and crank again untill i see fuel before i hook back up and it starts. seems like a glitch somewhere.
thanks,phil
I have no idea why you have to loosen a line at the carb to get it to start, whether it is draining back toward the tank or not.
Like I said previously, you can buy a check valve for very few bucks to splice into your fuel pump line to test your theory instead of wearing out your keyboard here.
thanks for your reply. my concern is that it takes 6 or 7 sessions cranking and then i have to take a fuel line off at the carb and crank again untill i see fuel before i hook back up and it starts. seems like a glitch somewhere.
thanks,phil
That's very dangerous, and it's a fire waiting to happen. Use a ketchup/mustard dispenser bottle instead to put fuel into the float bowl through the bowl vent tube.
Your fuel isn't draining back past the fuel pump, and gravity doesn't pull fuel uphill - it's evaporating from hot-soak. Welcome to carburetors.
Better yet, don't prime it at all. Do like a lot of us do and crank it for 5 seconds. Then let it rest for 10 seconds. Then crank it another 5 to start it up. Benefits: no hassle, no air cleaner removal, no fire danger, and the big plus: oil pressure already at the bearings at start up. Win-win.
I have no idea why you have to loosen a line at the carb to get it to start, whether it is draining back toward the tank or not.
Like I said previously, you can buy a check valve for very few bucks to splice into your fuel pump line to test your theory instead of wearing out your keyboard here.
Mike, is this the same brand and style as the one you use on your cars?
I have a fleet of garden tractors. Just a fetish of mine. About 20 of them are the same design, just different features and different engines. All have fuel pumps and all have the tank lower than the engine,
Three different kinds of engines. Kohler Magnum opposed twin, Kohler Command V Twin and Briggs Vanguard V Twin. The Briggs and the Command have the same kind of vacuum diaphragm fuel pump. The Magnum has a cam operated fuel pump.
The only ones that will start quickly after sitting idle for a week or so is the Commands. The Briggs and the Magnum, you crank and crank and crank and finally they will start. Both seem to have empty carburetors.
So, I bought three of these check valves a couple weeks ago and installed one on one of my problem children, thinking that fuel is draining back to the tank. So far, on one tractor, that hasn't made any difference. Still hard to start. I'll get around to installing the other two check valves but I have no confidence that the fuel siphoning back to the tank is the problem.
I think the problem is evaporation, just like me and almost everyone else of this thread thinks.
Small, low pressure fuel pumps are available and installing one would fix this problem. I just don't get too emotional over it.
You can re fill the float bowl thru the vent with the air cleaner off also
