1955 - motor shuts down when put under load | Ford Thunderbird forum club group 1955-2005 models
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1955 - motor shuts down when put under load

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stonefisher

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Thunderbird Year
1955
I normally need a little starting fluid when starting cold but after letting it warm up it runs fine. I can rev it up time after time and it does great. If I try to take it for a spin, it might go 500 feet it might go a mile but then shuts down like it ran of gas. Does anyone have any advice?

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when you say it acts like it is running out of gas, do you mean that the engine sputters, tries to keep running then dies, or do you mean that it quits like you turned off the key?
 
It sounds like you need to check your float level, and you flow out of the fuel pump. But I agree with cokefirst, a little more information please.
 
Yes, sounds like fuel starvation, check any fuel filters, carb bowl levels and fuel pump pressure AND volume (two different tests) BTW, make sure gas tank venting is working too.
 
Yes, sounds like fuel starvation, check any fuel filters, carb bowl levels and fuel pump pressure AND volume (two different tests) BTW, make sure gas tank venting is working too. And make sure the distributor is locked down tightly.
 
I normally need a little starting fluid when starting cold but after letting it warm up it runs fine. I can rev it up time after time and it does great. If I try to take it for a spin, it might go 500 feet it might go a mile but then shuts down like it ran of gas. Does anyone have any advice?
From what you are describing it sounds like a fuel delivery issue. Start by performing a fuel pressure and volume test. According to the service manual, the fuel pump pressure specification is 4.0 to 5.0 psi at 900 rpm and the volume specification is 1 pint in less than 45 seconds at 900 rpm.

Your car has two "filters" which attempt to remove debris from your fuel before it enters your carburetor. The first filter is the one in the glass bowl located in the fuel line as it makes its way from the fuel pump to the carburetor. The second "filter" is the one that is most often overlooked and forgotten. If you have changed your fuel filter recently, yet your car still suffers from poor acceleration, your problem may be a clogged fuel screen. This screen is located behind the brass fitting which connects your fuel line to the carburetor.

To clean your fuel screen, you first must remove the fuel line from the brass fitting. On 1955 and 1956 Thunderbird's the fuel line should go to the back of the carburetor. Once the fuel line has been removed, unscrew the brass fitting from the body of the carburetor. There will be a gasket attached to the brass fitting. This gasket must be reinstalled behind the brass fitting, or your car will be leaking fuel. Inside the brass fitting will be a wire screen. This is your fuel screen. You can tap it out of the brass housing. Inspect the screen for sediment buildup. Your screen can be cleaned with carburetor cleaner. If your screen is bent or missing, you will need to order a replacement screen. Once your screen has been cleaned or replaced, reinstall the fuel screen back inside the brass housing. Reattach the brass housing to the carburetor. Do not forget to reinstall the gasket. Once you have installed the brass housing reconnect the fuel line. If your screen was clogged, you should notice a definite improvement in your car's performance.

As far as the fuel tank venting, the gas cap on your T-Bird must be vented to allow air to enter the tank. If air cannot get into the tank a vacuum will be created which can stop the flow of fuel to your engine. To vent the fuel tank, the 1955 and 1956 gas caps have a rib stamped into the surface which allows air to enter from the outside edge of the cap to the center.

Fuel Cap 1.jpg

The problem with the gas cap is that sometimes the inside diameter of the gasket was so small that it prevents the venting process. The problem can be easily repaired by removing the gasket from the gas cap and increasing the inside diameter of the gasket by cutting it with a razor blade.

doug7740
1955 Thunderbird Blue

Fuel Cap 2.jpg
 
Sounds like a venting problem, however...
You might also check for debris inside the fuel tank that may be periodically blocking the fuel pickup tube. Sometimes a piece of paper towel, piece of rag or other item innocently finds its way into the tank, floats around in the tank and when the car is moving, the fuel pump sucking gas from the tank and the debris finds its way to the pickup tube blocking/restricting the fuel flow. When the car shuts off, the debris floats/moves away from the pickup tube.
 
Of course, my post would only be relevant if the carb had ever been rebuilt, or the car run for any extended time on gasohol. Otherwise, running for a couple miles and then sputtering was my issue, and thus resolved. Changing the needle & seat is a simple operation. Finding the NOS brass parts though might be otherwise (?).
 
I think the previous comments hit the nail on the head, but if not here is something to check, especially if you worked under the car before this started. I had a 1968 Tbird that had the same issue after the exhaust system had been replaced. I finally discovered that they bent my fuel line and cut off most of the flow. There was enough getting through to idle, but under load it became fuel starved and the engine quit. It took me a while to figure that one out.
 
when you say it acts like it is running out of gas, do you mean that the engine sputters, tries to keep running then dies, or do you mean that it quits like you turned off the key?
Don't use the either based starting fluid can cause damage . We use Berman b12 also will clean carb jets. Maby power valve in bottom of carb. Check to see if pump jets are working if its not venting it would run till all the air is out of the tank then it would die.



when you say it acts like it is running out of gas, do you mean that the engine sputters, tries to keep running then dies, or do you mean that it quits like you turned off the key?
 
60 years of driving classic cars of all makes and I've never once used starter fluid, don't even know what a can of it looks liked...
 
I had same type issues on my 56. It felt fuel starved as it studdered, shuddered, bucked and died upon acceleration but ran fine parked at idle and reving..... I used most all the suggested diagnosis suggestions mentioned above.

I inspected ignition system and checked dual vacuum distributor. Both were fine from what I could test or measure.

Fuel system. Fuel line screen/filter behind Holley 4000 carb had a blob of gunk in it. The glass filter was replaced. Neither filter remediations fixed it. Pulled tank and was rusted and had grey chunks of stuff in it. Sock was gone. I replaced tank and fuel guage/sender (since I was in there). I inspected and blew out the steel fuel lines, replaced the flexible line leading to the fuel pump and the fuel hose from the tank the the steel lines. Still didn't fix it. Fuel pump was supposed to be good as prior owner had just replaced but I didn't test it. Yes, the fuel pump was the issue BUT it was because the pump arm was just loose enough to partially slip off the eccentric on the cam and the arm rubbed enough on it to pump fuel at parked idle or reving. The evidence was the side to side wiggle in the pump arm and the inside of the arm (closest to engine side) showed grinding marks on it meaning the arm was rubbing on the outside of the eccentric. I'm guessing the pump was misaligned at installation... So, test your fuel pump as suggested in earlier post for both pump pressure AND volume...

For my car. ALL the fixes were definately needed....eventually... I just got to do them all at once. 🤣
 
doug7740 covered all the bases, expanding on my previous short diagnosis...
Until you have looked into those obvious issues and eliminating them, you're wasting time.

The fuel pump volume and pressure tests alone will eliminate 70% of what has been discussed piecemeal in this thread..
 
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