Fuel issue

[Anonymous]

Hello, New to site. I need help with fuel siphon.Ihave a 65 Stang with a 200 and mechanical fuel pump. The problem is when car sits for a couple of days it will not start. Fuel has siphoned back to tank. Is there a check valve in pump or somewhere else in fuel system? A littlehead pressure on fuel tank and it fires right up. What in the fuel system stops fuel from draining back to tank?Thanks Bob Black

 

[addo]

Bob, the fuel pump does have little valves in it that should stop this happening.

It's also possible that the tank vent is slightly blocked, and this is causing a mild vacuum at some times. The ¼" steel vent line is located near the filler hose, and I can say from experience that they do get clogged (around here, by mud-daubing wasps).

As the carb is vented to atmosphere, it's also possible that some fuel is evaporating as the vehicle sits - perhaps more so from heat soak after shutting off.

Out of curiosity - are you parking the car with its nose slightly uphill?

 

[fordconvert]

Normally there should be enough fuel in the carb to get started and therefore get the fuel pump going again. My 66 with the autolite 1100 will start and idle for over a minute with the fuel line off the pump.

After a few days when it does this does it fire/pop at all when you first crank it and then die?

Are you sure there is no fuel in the carb? A choke or accel pump problem could have the same symptom. You can pull the air cleaner, hold the choke open with your finger, and stroke the throtte a few times looking down the throat, you should see 2 or 3 steady squirts of fuel. After that the choke should spring shut.

What carb do you have?

How long since the carb has been apart/ rebuilt?

Anything that would cause extra heat under the hood? Cracked manifold? Leakey headers?

How well does it re start on hot days?

Guys, Do any of the carbs found on these cars have any places to leak fuel out of the bowl (when sitting level)? Like the Rochesters that had the freeze plugs?

 

[Anonymous]

Bob, the fuel pump does have little valves in it that should stop this happening.

It's also possible that the tank vent is slightly blocked, and this is causing a mild vacuum at some times. The ¼" steel vent line is located near the filler hose, and I can say from experience that they do get clogged (around here, by mud-daubing wasps).

As the carb is vented to atmosphere, it's also possible that some fuel is evaporating as the vehicle sits - perhaps more so from heat soak after shutting off.

Out of curiosity - are you parking the car with its nose slightly uphill?

Thanks for the help. I should have been more clear. Yes the engine starts off of fuel in the carb but it will not draw it from tank. Will take a look a t vent line. Will start and run if I put air pressure in tank. Thanks again I will let you know. Also car has beeen parked in many diiferent attitudes. Bob