1955 292 w/Teapot stumbling

zeroroadkill

zeroroadkill

BlackBird Fly
Gold Member
Last seen
Joined
Mar 2, 2020
Thunderbird Year
1955
Carb professionally rebuilt
New gas tank
Flushed fuel lines
New fuel pump
New fuel filter
Max vacuum at idle
Sometimes she will start out ok acceleration but today after all the fixes she started to stumble at 40mph on smooth acceleration. Had to pump her to keep running. Then she ran fine! Sounds like fuel delivery to me???
Checked float level = ok
Fuel filter bowl full
No debris

another problem is when she sits for a couple of days she is hard to start. Initially a couple of pumps she’ll fire but die and it takes a lot of cranking to get her started. Usually have to use ether. I assume there is fuel at the accelerator pump but maybe the float bowl is empty? The fuel filter bowl is full. Need to check float bowl before next try.

any suggestions?
 

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She was cold! Just a mile from my house.
been down that vapor lock road before when she was getting really hot!
 
Under acceleration
I need to check the fuel pressure
 
Quit using starting fluid. It's hard on the engine. Carb Cleaner or Brake cleaner works better and is cheaper. Will not make it kick back or lock up while starting.
 
Yah, fuel supply is your issue. I thought of the fuel pick-up in the tank, but with a new tank, I assume that was addressed. Either the pump is faulty or you have a restriction somewhere. Pressure/ volume check is wise. Not all new work means it's done right.
 
OK, first I connected a fuel pressure gauge to the input pipe to the fuel filter. Started the engine and no pressure. It too about 10 seconds before gas started to flow! Looks like the pump is losing prime and maybe draining back to the tank? I might install a fuel backflow preventer.

Second I pulled the top off the float bowl and it was dry! This is why it's hard to start after sitting. The fuel filter bowl stays full, but no pressure and new fuel from the pump for 10 seconds! It appears that the power valve which has a spring-loaded stopper in it might be leaking fuel causing the float bowl to empty???
What keeps the float bowl full? Can fuel leak down through the main metering jets or the power valve??

I filled the float bowl full of fuel, covered it, and will check the level in the morning.

If the float bowl drys out and it takes 10 seconds of cranking to get fuel pressure to fill it, this answers why it takes so long to start after sitting!

I have two new carb kits 15136 and the power valves do not match what is in the carb! They are not spring-loaded like the one installed.
See pics.

Any suggestions?
float bowl.jpg15136 power valve.jpgcarb kits.jpgfloat bowl.jpgpower valve 2.jpgpower valve.jpgtwo different power valves.jpg
 
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In your pictures you are showing the needle & seat assembly from the carburetor rebuild kits, that's why they don't look like your power valve. Power valves are not included in the carburetor rebuild kits.

doug7740
1955 Thunderbird Blue
 
HAHA no wonder!!!! Do you know how to get a new power valve?
 
OK, checked float bowl this morning and it was still full! Fuel loss must be evaporation from a hot engine then?
Does anyone know where to get a ceramic carb manifold spacer gasket? Might help to keep carb base from getting so hot???

Thanks
Bob
 
Zoopie said:
The "rubber" one works well for mine, do you have any spacer under carb currently?
Click to expand...

No. Where did you get the rubber one? How thick is it? Does the air filter still clear the hood?
 
I also added TWO gaskets for top and bottom of spacer due to rigidity of the spacer.
 
Since you stated that the fuel is draining back to the tank and it takes about 10 seconds before gas starts to flow, shouldn't you correct your defective fuel pump issue before you worry about replacing the carburetor base gasket?


doug7740
1955 Thunderbird Blue
 
Yes, I have tried 3 fuel pumps. Two just wouldn't pump very well. This new one does work and I think I'm going to install the anti-siphon valve on the fuel line to the pump. The spacer is for trying to keep the carb base from getting so hot and evaporating the fuel in the float bowl. If there is a siphon effect from fuel draining back into the fuel tank through the pump, the anti-siphon valve should solve this. I just don't understand why others are not having this fuel problem?

As far as the carb spacer, I do have more gaskets, so maybe I'll try stacking 5...

Gasket stack in under carb (hood still clears wingnut) and anti-siphon valve on the fuel line to pump, we will see.....
Stay tuned...

nope!
Sat for four days. Accelerator pump gave a couple of squirts, she started and died. Crank, crank, crank...
I didn’t pull the float bowl top off, just frustrated!

Question
If I install a primer pump at the gas tank will it push fuel through the mechanical fuel pump?

thanks
 
Electric fuel pumps are designed to push fuel and they loose efficiency when pulling fuel from the tank. I do not recommend by passing the mechanical fuel pump when an electrical pump is installed. It is installed for back up and used only to over come a vapor lock if necessary or cold starts if the vehicle has been setting for a long period of time especially on 1955/56 models. They are designed to allow fuel to pass through when the mechanical only pump is in use and can be used to augment the mechanical pump when the engine starts to surge at the onset of a vapor lock.

CASCO sells an electric fuel pump kit in both 6 and 12 volts. Here's the link:

www.classictbird.com

Electric Fuel Pump Kit - 12 Volt - 1 Per car-classictbird.com

Electric fuel pump: Is mounted in-line with the original fuel pump. If you want to run it full-time, we suggest you install an oil sensing pressure switch that can turn off the pump in the case of an accident. Pump operates @ 1.3amp and makes 2.5-4psi WHY WOULD I NEED AN ELECTRIC FUEL PUMP...
www.classictbird.com

doug7740
1955 Thunderbird Blue
 
Doug,

Do you know why fuel disappears from the float bowl over time? Is the power valve or main metering jets leaking fuel into the intake manifold? Wouldn't this "wash" the cylinders (bad)? Is it the Holley 4000 carb? Do 57's have this problem? If you didn't want to install a switch under the dash or run it continuously could you tap off the starter solenoid so it just gets power when the starter is activated?

Thanks
 
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