55 carb advise

[Waltweems]

My 55 has the original carb and the car runs great, but I always have to pump the throttle several times to get it to start. After sitting a few days I may have to pump it 8-10 times. Once started it will restart easily for that day.
I would like to fix it. Can anyone advise me as to where to start?

Thanks,

Walt

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[Tater Salad]

Some have added an inline electric pump to fill the fuel bowl prior to attempting a start. Just make sure it's low pressure and you turn it off after a couple of seconds. Seems to me a check valve would work too. But I haven't tried either one, yet

 

[Dale Leonard]

It sounds like your accelerator pump is worn out. Next time before starting, remove the breather and look down into the carburator. while watching, manually pump the throttle. If you do not see it squirt gas into the bore of the carburator you will need to install a new accelerator pump.

 

[Tater Salad]

Some have added an inline electric pump to fill the fuel bowl prior to attempting a start. Just make sure it's low pressure and you turn it off after a couple of seconds. Seems to me a check valve would work too. But I haven't tried either one, yet

Does the fuel filter still contain fuel after the car sits for several days? If so, then Dale is most likely spot on.

 

[Dale Leonard]

Does the fuel filter still contain fuel after the car sits for several days? If so, then Dale is most likely spot on.

I looked at it this way. If the needle and seat was not working correctly then the car would flood. Also the needle is normally in the top of the carburator and if the fuel siphons back to the tank due to a faulty fuel pump then it cannot drain the fuel bowl as it would only have an empty fuel pump and line to the carburator. The accelerator pump would still give enough gas to start the car. When he said that he had to pump it 6 or more times I figured that he was not getting an initial shot of fuel. You idea with the electric fuel pump works also. Have seen that done many times.

 

[Tater Salad]

I looked at it this way. If the needle and seat was not working correctly then the car would flood. Also the needle is normally in the top of the carburator and if the fuel siphons back to the tank due to a faulty fuel pump then it cannot drain the fuel bowl as it would only have an empty fuel pump and line to the carburator. The accelerator pump would still give enough gas to start the car. When he said that he had to pump it 6 or more times I figured that he was not getting an initial shot of fuel. You idea with the electric fuel pump works also. Have seen that done many times.

Thanks for that info Dale. My car was first dumping fuel into the engine via the fuel pump. I bought a new pump and that solved the problem of fuel into the oil however it still siphoned back to the tank when the car sits for several days. I haven't had the new or old fuel pump apart, so I'm not sure if they have a check or just the diaphragm to maintain fuel above the pump when stored. If you have any information on those pumps id greatly appreciate it.

 

[Dale Leonard]

That pump uses a diaphragm to pump the gas and if I am correct it has to have a check valve in it to force the pump to pump in one direction only. It could be that you are pulling a slight vacuum on yur fuel tank and that is forcing the fuel to bypass the check valve and is sucking the gas back to the tank. Make sure the vent is open on the gas tank. Also the spring on the check valve may be weak in the fuel pump. Hope this helps .

 

[Philt]

I have had this issue in mind since buying my 56 a few months ago. A friend ( a excellent commercial pilot and a natural mechanic ) has a 55. Have not found a discussion else where, so here is a newbies thinking. Real world guys please chip in..
First I agree with Dale, check the squirters to see if they are working. Be sure the bowel is full. Another hint of a weak accelerator is of course a stumble when you try to accelerate. Make sure the ignition system is strong. Fresh coil, wires and plugs. These are old cars and need all the spark they can get to start and the antique starters take a lot of amperage.
Think I will change mine to a gear reduction starter when the budget allows.
Second,if the pump has a check valve ( do they all?) then the line from the pump to the Teapot Holly should stay charged with fuel. Only evaporation over along period could empty it completely. Looking at the Holly 4000 shop manual, and the position of the fuel line, it looks like it would be unlikely the carb bowel would drain back much if the pump line is charged and held by the fuel pump check valve.
Lastly the line from the tank to the pump looks the most likely candidate for drain back. A in line check valve, cheap and readily available might service. But any opening pressure over say 1 lb invites interruption to the pump and cavitation with possible damage to the pump.
Summary: If the accel pump is healthy, and the fuel pump has a functioning check keeping the supply line and carb bowel charged, that leaves the line between the tank and fuel pump to keep wet.
Conclusion: My bird will likely sit for weeks at a time and I do not relish a road side changing mechanical fuel pump. The advantages of a in line electric fuel pump, regulated to a about 3 psi would allow me to prime the tank to pump line , the pump body and carb. With a DPDT switch I can prime, prime and/or run on the pump and provide a redundant pump so I can get home. Electric kits available from at least one tbird supplier or the round or square electric pumps widely available.
Look ward to hearing responses.

 

[Tater Salad]

That pump uses a diaphragm to pump the gas and if I am correct it has to have a check valve in it to force the pump to pump in one direction only. It could be that you are pulling a slight vacuum on yur fuel tank and that is forcing the fuel to bypass the check valve and is sucking the gas back to the tank. Make sure the vent is open on the gas tank. Also the spring on the check valve may be weak in the fuel pump. Hope this helps .

Well, that's I fine point. The cap I have on now may be doing exactly what you stated. I'll check that out. Thanks much Dale.

 

[Dick Rupp]

I have had four '55 birds. They all started hard after sitting awhile. The engines are cold blooded. Pump the gas pedal a couple times to activate the choke. Hold the pedal to the floor and crank away. That's what I do. It works every time for me.