1955 292 w/Teapot stumbling

[doug7740]

As far as the fuel disappearing from the float bowl, the problem is not the carburetor it's the fuel pump. Normally, when you haven’t driven the car in four or five days, all of the gas has drained out or evaporated from the fuel pump. Classic Auto Supply sells a fuel line check valve that will eliminate this. The part number is 9160CV.

https://www.classictbird.com/Check-Valve-Fuel-Line-Fuel-Pump/productinfo/9160CV/

To make sure it’s not the carburetor, disconnect the fuel line at the carburetor inlet and then wait 3 to 4 days. Check the fuel level in the float bowl and I bet you it will be full.

If you are looking for information on how to wire the electric fuel pump, I would wire it to the “I” terminal of the ignition switch and then through another on/off switch. That way it will only be on while the engine is running and you can turn it off if you want to. You could also wire it through the oil pressure switch with a relay, that way if the engine dies in case of accident once oil pressure is lost the pump will shut off.

doug7740
1955 Thunderbird Blue

 

[zeroroadkill]

As far as the fuel disappearing from the float bowl, the problem is not the carburetor it's the fuel pump. Normally, when you haven’t driven the car in four or five days, all of the gas has drained out or evaporated from the fuel pump. Classic Auto Supply sells a fuel line check valve that will eliminate this. The part number is 9160CV.

https://www.classictbird.com/Check-Valve-Fuel-Line-Fuel-Pump/productinfo/9160CV/

To make sure it’s not the carburetor, disconnect the fuel line at the carburetor inlet and then wait 3 to 4 days. Check the fuel level in the float bowl and I bet you it will be full.

If you are looking for information on how to wire the electric fuel pump, I would wire it to the “I” terminal of the ignition switch and then through another on/off switch. That way it will only be on while the engine is running and you can turn it off if you want to. You could also wire it through the oil pressure switch with a relay, that way if the engine dies in case of accident once oil pressure is lost the pump will shut off.

doug7740
1955 Thunderbird Blue

I did the test but only for 24 hours, it was still full. I installed an anti-siphon check valve on the fuel line going to the pump, but it still needed to crank over several minutes to start. I've checked for leaks, none. Even if the pump was draining back to the tank the float bowl should still be full and the engine should start and run with the fuel in the float bowl before the pump can prime and refill the bowl. I'm going to pull the top off today and see what the fuel level is in the float bowl.

I did install the 9160CV check valve but it took too much pressure to get fuel through it so I installed a check valve that only takes .02bar of pressure (2.9psi).
Since this is the second new fuel pump, one of which didn't pump, maybe it's the pump. I noticed that under moderate acceleration she will sometimes cut out and I have to keep pumping her to keep going, but then will run fine...???

 

[zeroroadkill]

Float bowl dry!!! so it’s draining into the intake or evaporating !

 

[doug7740]

Was the fuel line at the carburetor still connected to the fuel pump before you checked to see if there was fuel in the float bowl? The only way you will know if it is draining into the intake is to isolate the carburetor from the rest of the fuel system.

The Holley 4000 is notorious for hard starting after sitting for a few days. Since I'm a purest my 1955 Thunderbird still has a 6 volt, positive ground electrical system, it still has points and condenser ignition system, and a Holley 4000 carburetor with a mechanical fuel pump only.

Since I drive my car about 1,500 miles a year in all different temperatures, I had to learn the best way to start my car under the different driving conditions. I don’t worry about vapor lock, because I only use 100% gasoline in my car. No ethanol fuel ever.

This is the procedure I use to start my car:

Cold Engine - Sitting Overnight - Sitting for A Few Days

1. Do not touch the accelerator; crank the engine over for 5 seconds.
(This not only fills the fuel bowl with fuel, it also builds up oil pressure)

2. Slowly push the accelerator pedal to the floor and then slowly release the accelerator pedal.
(This closes the choke assembly and primes the carburetor with fuel)

3. Do not touch the accelerator; crank the engine over for 5 seconds. If the engine starts, rev the engine once slightly.

4. If the engine did not start, depress the accelerator 3 times, but only ¼ pedal travel each time.
(This primes the carburetor with additional fuel, but keep in mind, T-Bird engines flood easily)

5. Crank the engine over once again and when the engine starts, rev the engine once slightly.

Warm Engine - Sitting Less Than an Hour

1. Do not touch the accelerator; crank the engine over and when the engine starts rev the engine once slightly.

Warm Engine - Sitting More Than an Hour

1. Depress the accelerator pedal ¼ pedal travel and hold it in that position. Crank the engine over and when the engine starts rev the engine once slightly.

doug7740
1955 Thunderbird Blue

 

[zeroroadkill]

With the anti-siphon check valve, I do not see the difference. It appears that the TEAPOT allows seepage into the intake manifold. This bothers me because that fuel seeps beyond the open intake valves that are open and can "wash" the cylinder walls of oil. I'd like to know why this happens and a solution to stop the leakage.

 

[doug7740]

The carburetor could be boiling over (percolating). This happens when the engine gets hot and you turn it off. The fuel having a lower boiling point will boil and evaporate, causing the float bowl to dry. Make sure the fuel lines are away from the manifold, or try other brands of fuel. As I said, I only use 100% gasoline in my Thunderbird and I’m not having any problems as long as I use the starting procedures that I mentioned earlier.

The Holley 4000 carburetor is a very good carburetor and probably one of the most misunderstood carburetors in existence. The average mechanic takes one look at it and has no idea how to properly adjust or rebuild this model. I have rebuilt quite a few without any problems.

As I said, the Holley 4000 is notorious for hard starting after sitting for a few days. That’s why some have gone as far as adding an electric fuel pump which they use only before starting to fill up the float bowl. If you think the fuel is seeping in the intake manifold from a defective carburetor (porous casting), then I suggest you replace the carburetor.

doug7740
1955 Thunderbird Blue

 

[zeroroadkill]

The engine was just warm. I started it just enough to fill the float bowl. I only use non-ethanol fuel too. I’ve ordered the electric fuel pump!

 

[suzukiridr]

Have you thought about installing an electric fuel pump? That should solve all your problems.

 

[Scooter]

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?

Have you checked the flex line into the fuel pump? Could be sucking air?

 

[zeroroadkill]

Have you checked the flex line into the fuel pump? Could be sucking air?

Yeah, I read that the fuel pump can allow fuel to siphon back to the tank, so I put in a check valve at the fuel line, no difference.
Another cause is that the fuel pump leaks into the central chamber and leaks into the crankcase! Bad.....
I smelled the oil and it did have a slight gas smell, but on ignition when exposed to a flame. Whatever that means? Anyway I'll see if the float bowl is down in a few days eliminating the pump. If it's down (on a cold engine when filled so no evap), it's gotta be leaking from the carb float bowl, power valve???

More to come...

Have you checked the flex line into the fuel pump? Could be sucking air?

no leaks

UPDATE on fuel leakage from float bowl:

Test procedure:
Cold engine
Remove fuel pump from the engine
Disconnect the fuel line from the carburetor
Remove the top off of the float bowl
Fill the float bowl with fuel and check that needle and seat are not leaking
Cover the carburetor with a plastic bag to prevent evaporation
Let sit 24 hours
Fuel level in the float bowl down

Conclusion:
Fuel is not leaking back through the fuel pump!
Float bowl needle and seat are not leaking out
Gas going into the intake manifold
Oil has a faint smell of fuel so fuel must be washing down some cylinders

Does anyone have an answer besides replacing the carburetor with a modern Holley 390 and a different distributor?

Thanks