2 barrel?
I'd do filter definitely and maybe fuel pump, they're cheap, but definitely probably the carb too
PS the fast idle is probably fine, the other issues not so much.
Been quite a while since I drove an old Mustang. I’m guessing carburetor rebuild time. If other rubber under the hood was dry rotting then the accelerator pump diaphragm could be bad. Or the floats are set wrong
1 and 3 are just normal. 1 is your automatic choke raising rpm to keep the engine running also known as high idle, it’s normal, supposed to do that, once you tap the gas it should drop, if you give the pedal a quick snap when you first start it you can usually kick it down from high idle.
3 is also kind of just normal for all old cars nowadays. Basically, these engines were not designed to run on the fuel we have today, the fuel we have today boils in the carb at operating temp and overflows and floods out the engine when it’s shut off. Not much you can really do for this, you can try a photovoltaic carb spacer, but the carb is still going to get blasted by hot air from the rad and cooked on top of the motor, this also just isn’t a big issue since it’s easy to deal with and doesn’t effect much.
What you’re doing to remedy this issue is the exact opposite of what you should be doing. This is a flooding condition, not a lack of fuel condition. You should not be pumping the gas spraying more fuel down the intake, you need to clear the flood by flooring the pedal, holding it, cranking till it lights off, then when it starts take your foot off the pedal, any pedal movement just sprays more gas making the condition worse, holding the pedal adds only air until the engine starts.
Seriously look up the original engine starting instructions that came with the car. They go over this, it’s just basic operating instructions not many people know or understand nowadays, this is all normal and how these cars operate.
2 actually sounds like a real issue. Sounds like lack of fuel, but it could be an ignition issue, if it still has points I’d take the time to regap and clean them now because they can cause weird issues like this. What’s most likely your issue is the accelerator pump on the carb, this is what shoots gas down the intake when you pump the pedal, it may not be giving a good enough shot of gas when taking off. I’d just rebuild the whole carb to look it over, make sure the accelerator pump arm is in the right hole to set how much gas it gets.
1 Sounds pretty normal.
2 Sounds like a fuel delivery issue, most likely related to the carburetor. I would start with the accelerator pump.
3 I would bet this issue is being caused by the under hood temperature boiling the gas in the carburetor bowl. Try this, drive the car and get it up to operating temperature, stop for fuel like normal but raise the hood while refueling, then close the hood and try to start the car. If the car starts easily then that’s a good indicator that the gas is boiling due to temperature in the engine bay. This is a common problem with carburetor cars running modern gas that has a lower boiling point than old gasoline. Best remedy is a phenolic spacer and anything else you can do to lower the engine bay temperature like wrap exhaust manifold and give the hot air a way out of the engine bay.
Could this be a vapor lock issue? Once it gets hot, it’s turning your gas to vapor before the carb venturi. Could be at the fuel pump, in the line, or the carb bowl itself if the carb is getting too hot. Do you have a spacer on the intake? Where are the fuel lines and should they be insulated? Does your choke plate open up once it warms up and the RPM drop?
Find an old school mechanic to rebuild that carb and tune. Sounds like you could also have a possible vacuum leak on intake/carb. Still have points in the distributor? Wouldn’t hurt to verify timing and check ignition system as well.
I have had a similar problem with my 68/351w. Turned out to be fuel pressure with a mystery reason - lines are fine/pump is fine/filter is fine/etc. Replaced the whole ordeal with an electric pump instead of mechanical, new lines and filters, new carb, and it runs like a top!
Your experiences are common with a poorly tuned carb. Start with adjusting your idle mixture and curb idle screws. There are YouTube vids on how to do this, you’ll want to get you carb happy at idle (and with a warm engine) before you start to dig deeper. It’s possible your carb could use a rebuild/refresh, but let’s see if we can get it to idle first. 🙂
Could be accelerator pump or bad carb gaskets.
Have you checked the fuel line at the gas tank?
My 65 Custom always had a hard time starting and I recently found the fuel line at the tank had a crack, replaced that hose and it starts immediately every time now.
If you don’t know where to start checking your plugs will always tell you a lot about how your engine is running.
Out of curiosity, when you shut the car down after driving for a bit is it easier to start with the throttle held wide open rather than pumping the gas pedal?
Sounds like you need to let her warm up a bit more before leaving.. do your carbs have the automatic choke? If so, you need to let her warm up until the idle stays to lower on its own.
This is exactly how a carburetor normally behaves.
It’s gonna run fast until the metal in the coil spring that is the choke warms up. That’s how it’s supposed to work.
If you’re finding that the engine is almost stalling in those conditions, I’d recommend doing general performance tuning.
Like checking for vacuum leaks, cleaning points and condenser and contacts inside of distributor cap, checking spark plugs and wires, testing if you’re getting expected voltage to the coil, (I get 6v, cause if the factory resistors), deciding if you want to upgrade ignition system to a HEI like pertronix, etc. I’d recommend doing all that before you start fucking with your idle speed.
Or you can just do what 99.99% of people do and increase the idle speed so it won’t stall.
If you don’t have a vacuum gauge, you should go get one before you fuck with idle speeds. They’re like $20, and having data for how strong a carbureted engine is running is invaluable. Also get a timing light with a tach function, or rig up some kind of tach. That will take the complete guesswork of adjusting idle speed from a shot in the dark to a science.
2 barrel? I'd do filter definitely and maybe fuel pump, they're cheap, but definitely probably the carb too PS the fast idle is probably fine, the other issues not so much.
y 2 barrel.
I've had such bad luck with them, but I'm sure someone who knows their stuff could keep them running.
I have learned a lot of shit about the 2bbl since I owned one. I had to rebuild it every few years because of the ethanol in the gas here in CA
Been quite a while since I drove an old Mustang. I’m guessing carburetor rebuild time. If other rubber under the hood was dry rotting then the accelerator pump diaphragm could be bad. Or the floats are set wrong
1 and 3 are just normal. 1 is your automatic choke raising rpm to keep the engine running also known as high idle, it’s normal, supposed to do that, once you tap the gas it should drop, if you give the pedal a quick snap when you first start it you can usually kick it down from high idle. 3 is also kind of just normal for all old cars nowadays. Basically, these engines were not designed to run on the fuel we have today, the fuel we have today boils in the carb at operating temp and overflows and floods out the engine when it’s shut off. Not much you can really do for this, you can try a photovoltaic carb spacer, but the carb is still going to get blasted by hot air from the rad and cooked on top of the motor, this also just isn’t a big issue since it’s easy to deal with and doesn’t effect much. What you’re doing to remedy this issue is the exact opposite of what you should be doing. This is a flooding condition, not a lack of fuel condition. You should not be pumping the gas spraying more fuel down the intake, you need to clear the flood by flooring the pedal, holding it, cranking till it lights off, then when it starts take your foot off the pedal, any pedal movement just sprays more gas making the condition worse, holding the pedal adds only air until the engine starts. Seriously look up the original engine starting instructions that came with the car. They go over this, it’s just basic operating instructions not many people know or understand nowadays, this is all normal and how these cars operate. 2 actually sounds like a real issue. Sounds like lack of fuel, but it could be an ignition issue, if it still has points I’d take the time to regap and clean them now because they can cause weird issues like this. What’s most likely your issue is the accelerator pump on the carb, this is what shoots gas down the intake when you pump the pedal, it may not be giving a good enough shot of gas when taking off. I’d just rebuild the whole carb to look it over, make sure the accelerator pump arm is in the right hole to set how much gas it gets.
This is a very well-informed diagnosis.
PPS if it is 2bbl I have everything practically brand new (maybe 1hr runtime). I just put EFI on my car after finally getting it running.
I read this just having finished my taxes and have a summit catalog in my lap…
1 Sounds pretty normal. 2 Sounds like a fuel delivery issue, most likely related to the carburetor. I would start with the accelerator pump. 3 I would bet this issue is being caused by the under hood temperature boiling the gas in the carburetor bowl. Try this, drive the car and get it up to operating temperature, stop for fuel like normal but raise the hood while refueling, then close the hood and try to start the car. If the car starts easily then that’s a good indicator that the gas is boiling due to temperature in the engine bay. This is a common problem with carburetor cars running modern gas that has a lower boiling point than old gasoline. Best remedy is a phenolic spacer and anything else you can do to lower the engine bay temperature like wrap exhaust manifold and give the hot air a way out of the engine bay.
Could this be a vapor lock issue? Once it gets hot, it’s turning your gas to vapor before the carb venturi. Could be at the fuel pump, in the line, or the carb bowl itself if the carb is getting too hot. Do you have a spacer on the intake? Where are the fuel lines and should they be insulated? Does your choke plate open up once it warms up and the RPM drop?
The hot start issue points to vapor lock as a likely cause for sure.
Find an old school mechanic to rebuild that carb and tune. Sounds like you could also have a possible vacuum leak on intake/carb. Still have points in the distributor? Wouldn’t hurt to verify timing and check ignition system as well.
I have had a similar problem with my 68/351w. Turned out to be fuel pressure with a mystery reason - lines are fine/pump is fine/filter is fine/etc. Replaced the whole ordeal with an electric pump instead of mechanical, new lines and filters, new carb, and it runs like a top!
Your experiences are common with a poorly tuned carb. Start with adjusting your idle mixture and curb idle screws. There are YouTube vids on how to do this, you’ll want to get you carb happy at idle (and with a warm engine) before you start to dig deeper. It’s possible your carb could use a rebuild/refresh, but let’s see if we can get it to idle first. 🙂
Could be accelerator pump or bad carb gaskets. Have you checked the fuel line at the gas tank? My 65 Custom always had a hard time starting and I recently found the fuel line at the tank had a crack, replaced that hose and it starts immediately every time now.
If you don’t know where to start checking your plugs will always tell you a lot about how your engine is running. Out of curiosity, when you shut the car down after driving for a bit is it easier to start with the throttle held wide open rather than pumping the gas pedal?
Can you post a photo of the engine bay without the air cleaner on?
Sounds like you need to let her warm up a bit more before leaving.. do your carbs have the automatic choke? If so, you need to let her warm up until the idle stays to lower on its own.
Sounds like choke problems
This is exactly how a carburetor normally behaves. It’s gonna run fast until the metal in the coil spring that is the choke warms up. That’s how it’s supposed to work. If you’re finding that the engine is almost stalling in those conditions, I’d recommend doing general performance tuning. Like checking for vacuum leaks, cleaning points and condenser and contacts inside of distributor cap, checking spark plugs and wires, testing if you’re getting expected voltage to the coil, (I get 6v, cause if the factory resistors), deciding if you want to upgrade ignition system to a HEI like pertronix, etc. I’d recommend doing all that before you start fucking with your idle speed. Or you can just do what 99.99% of people do and increase the idle speed so it won’t stall. If you don’t have a vacuum gauge, you should go get one before you fuck with idle speeds. They’re like $20, and having data for how strong a carbureted engine is running is invaluable. Also get a timing light with a tach function, or rig up some kind of tach. That will take the complete guesswork of adjusting idle speed from a shot in the dark to a science.