Carburetor or Fuel Pump Issue

[Mountain Dew]

My 46' Super De Luxe fires off in less that one revolution when I hit the starter button.......usually. If she sits for 4 or 5 days I have to put a little gas in the carburetor to get it to start. Sometimes I can see the low fuel level in the sediment bowl. If I drive around and shut the warm engine down, and let it cool, she turns over a few revolutions before she fires off. If I start it periodically and let the warm engine cool down slowly she fires off in less that one revolution and will start that way cold. It's like the fuel is cooking off from the carburetor or it's losing its prime. I see no fuel leaks. I'm not sure when she started doing this but the fuel pump has been replaced and so has the flexible fuel line. Do I have a carburetor issue or a fuel pump issue?

[mcgarrett]

Let's start by checking a couple of things...could be defective fuel pump diaphragm or power valve. Depending on how old they are, I would consider replacing them. At least you've taken a couple of potentially troublesome items off the table.

[Mountain Dew]

Power valve? Where is that located?

[mcgarrett]

Separate the alloy (pot metal) upper carb body from the cast iron base which has the throttle butterflies. Look at the underside of the pot metal carb body and you will see a valve screwed into it. This is the power valve. If they are old, they can fail to operate correctly or leak and cause the float bowl to empty into the intake manifold causing a flooding condition. Most new carburetor kits will have a new power valve, or you can purchase one separately from some of the Early V8 parts suppliers.

[ford38v8]

Originally Posted by mcgarrett

Separate the alloy (pot metal) upper carb body from the cast iron base which has the throttle butterflies. Look at the underside of the pot metal carb body and you will see a valve screwed into it. This is the power valve. If they are old, they can fail to operate correctly or leak and cause the float bowl to empty into the intake manifold causing a flooding condition. Most new carburetor kits will have a new power valve, or you can purchase one separately from some of the Early V8 parts suppliers.

This point needs clarification: New power valves have an incompatible base to the old carburetors, as the old had a flat surface of the sealing base, the new have a radius. These new units can be machined in a lathe to fit, or if buying from a supplier, verify that operation has been done. Alternatively, I've heard that some have used an el-cheapo method by utilizing two washers instead of the correct single, but as this seal is critical to the operation of the valve, I cannot recommend this method.

[JayChicago]

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Originally Posted by Mountain Dew

My 46' Super De Luxe fires off in less that one revolution when I hit the starter button.......usually. If she sits for 4 or 5 days I have to put a little gas in the carburetor to get it to start. Sometimes I can see the low fuel level in the sediment bowl. If I drive around and shut the warm engine down, and let it cool, she turns over a few revolutions before she fires off. If I start it periodically and let the warm engine cool down slowly she fires off in less that one revolution and will start that way cold. It's like the fuel is cooking off from the carburetor or it's losing its prime. I see no fuel leaks. I'm not sure when she started doing this but the fuel pump has been replaced and so has the flexible fuel line. Do I have a carburetor issue or a fuel pump issue?

I don't understand. What is the problem? All you have described seems perfectly normal to me. I don't see anything wrong here.

[Mountain Dew]

Originally Posted by JayChicago

I don't understand. What is the problem? All you have described seems perfectly normal to me. I don't see anything wrong here.

You say that it is normal to take the oil bath breather off and pour a little gas in the carburetor if the car has not ran in a few days?

[Mountain Dew]

Originally Posted by ford38v8

This point needs clarification: New power valves have an incompatible base to the old carburetors, as the old had a flat surface of the sealing base, the new have a radius. These new units can be machined in a lathe to fit, or if buying from a supplier, verify that operation has been done. Alternatively, I've heard that some have used an el-cheapo method by utilizing two washers instead of the correct single, but as this seal is critical to the operation of the valve, I cannot recommend this method.

What do you recommend? A new carburetor? Who rebuilds these carburetors? I think I might get a whole rebuild kit and give that a shot.

[chuck stevens]

Originally Posted by Mountain Dew

What do you recommend? A new carburetor? Who rebuilds these carburetors? I think I might get a whole rebuild kit and give that a shot.

We all have the same problem with this "new" fuel... it boils at a lower temperature and floods the warm engine. A heat block plate, goes under carb, will help some. Longer carb studs are needed.
Cold starts can be helped with an electric fuel pump and a spring loaded switch so it doesn't run all the time, just for priming. The carb wants only 2-3 lbs of pressure.

[mfirth]

What Chuck said x 2. Fuel today is crap & causes problems. Chuck stevens gets my vote before you start tearing stuff apart.

[rockfla]

Originally Posted by Mountain Dew

What do you recommend? A new carburetor? Who rebuilds these carburetors? I think I might get a whole rebuild kit and give that a shot.

IMO
I, for one, would start by checking ALL the fuel line connections and make 100% sure ALL are tight and not losing "seal". Then you can look to the above stated issues OR if you want to make sure all is 100% correct.....Box your carburetor and fuel pump up and send them to Charlie Schwendler, 5845 Cole Road, Orchard Park NY 14127......He IS the carb and fuel pump man and will make them right. I include a signed check with my stuff I send him and he calls me and lets me know whats what and sends my stuff back. Top notch fellow!!! I NOW have the same problem with my 39 Mercury, which I didn't have before I ran it out of gas.....I added an inline fuel filter at the rubber line from the firewall to the fuel pump and I suspect that one of the ends of my ADDED fuel filter is not 100% tight and is leaking vacuum over several days.

[Mountain Dew]

Originally Posted by rockfla

IMO
I, for one, would start by checking ALL the fuel line connections and make 100% sure ALL are tight and not losing "seal". Then you can look to the above stated issues OR if you want to make sure all is 100% correct.....Box your carburetor and fuel pump up and send them to Charlie Schwendler, 5845 Cole Road, Orchard Park NY 14127......He IS the carb and fuel pump man and will make them right. I include a signed check with my stuff I send him and he calls me and lets me know whats what and sends my stuff back. Top notch fellow!!! I NOW have the same problem with my 39 Mercury, which I didn't have before I ran it out of gas.....I added an inline fuel filter at the rubber line from the firewall to the fuel pump and I suspect that one of the ends of my ADDED fuel filter is not 100% tight and is leaking vacuum over several days.

The "FordBarn.com" is awesome! I always get great replies when I make posts with issues that arise. Yes....I want to make sure all is 100% correct before I write it off as being an ethanol or vapor lock problem.

Do you have Charlie Schwendler's phone number? You can PM it to me. I think it would be appropriate to talk before I send him parts and a blank check.

[Eddie Morgan]

Good morning! Thanks, mcgarrett !!! My first day in the barn and your answer to Mountain Dew may have helped me solve a problem I'm having with my Holley 1901 teapot carb. ..... fuel bowl emptying.

[51504bat]

Originally Posted by Mountain Dew

The "FordBarn.com" is awesome! I always get great replies when I make posts with issues that arise. Yes....I want to make sure all is 100% correct before I write it off as being an ethanol or vapor lock problem.

Do you have Charlie Schwendler's phone number? You can PM it to me. I think it would be appropriate to talk before I send him parts and a blank check.

Here is Charlie's contact info. It has been posted on my forums so no worry about putting it out there.
716 662 [email protected]

[mcgarrett]

For what it's worth, the link below shows a range of power valves available from Holley. I don't remember off-hand the correct vacuum rating for the one used in the Holley 94's, but someone here on the Barn will know. They work based on manifold vacuum and there are many varieties with different vacuum ratings as you can see...

https://www.holley.com/products/fuel.../power_valves/

[JayChicago]

Originally Posted by Mountain Dew

You say that it is normal to take the oil bath breather off and pour a little gas in the carburetor if the car has not ran in a few days?

Yes, after 4 or 5 days the fuel in the carb can evapaorate enough to be low. I usually don't pour gas in, but do have to crank a while to get gas up. I crank in 5 second intervals to not overheat the starter. Depending on how long the car has sat, may need to do that two or three times. Choke fully closed while cranking creates a vacuum in the carb to help pull in fuel.

Kube has advised to close the choke all the way when parking for storage, as that may delay evaporation somewhat.

[Mountain Dew]

Originally Posted by JayChicago

Yes, after 4 or 5 days the fuel in the carb can evapaorate enough to be low. I usually don't pour gas in, but do have to crank a while to get gas up. I crank in 5 second intervals to not overheat the starter. Depending on how long the car has sat, may need to do that two or three times. Choke fully closed while cranking creates a vacuum in the carb to help pull in fuel.

Kube has advised to close the choke all the way when parking for storage, as that may delay evaporation somewhat.

My '46 is a little beyond the sceneiro you described. Cranking and choking will not do it. I have to put fuel in the carburetor to start it. Sometimes the fuel level is down in the sediment bowl after a few days. Cranking does not seem to raise the level. The pump works fine when the level is up in the sediment bowl.

[JayChicago]

Common problem I have heard is the gasket on top of the glass sediment bowl. Slightest air leak anywhere on the suction side of the fuel pump is a problem. Pump will suck air before it sucks fuel. Easy thing to try first is remove the sediment bowl and clean/reset or replace that gasket.

[CA Victoria]

Had a similar issue. It had a Rebuilt fuel pump & carb. The aux. elect fuel pump added solved this issue. I wired it thru a momentary-off-on switch & use it to prime and backup my mechanical pump.

[Bill OH]

Install an electric fuel pump at the tank operated by a switch on the dash, which in turn is connected to the ignition side of the ignition switch. Using longer carb studs, put 5 carb to manifold gaskets under the carb. Prevents heat soak into the carb.I no longer have the hard start problems. It has not been discussed, but is the line from the tank to the fuel pump good or does it have holes - turning on the electric fuel pump at the tank will show a defective gas line. I installed a 5/16ths copper line in 1988 and no problems. I used a neoprene gasket on the mechanical fuel pump filter bowl - cork can develop an air leak.

[Mountain Dew]

I'll try a new neoprene gasket on the fuel pump and check out the gas line to the tank.

[tubman]

I've had the opposite experience with fuel pump bowl gaskets. I have found that cork gaskets work better for general use. Neoprene may last longer, but it gets hard after a few years.

[ford38v8]

Originally Posted by Bill OH

I installed a 5/16ths copper line in 1988 and no problems.

I used a neoprene gasket on the mechanical fuel pump filter bowl - cork can develop an air leak.

Copper is not a good choice for a fuel line due to work hardening causing failure. Gasoline is not what you want to leak under your car. Your original line was copper plated rolled steel, which is still available. A newer product, Cuproweld, beats all competition for ease of use and longevity.


This is the first time I've heard a recommendation to use neoprene over cork. Cork will perform well forever, while neoprene ages quickly. Soak your cork in oil for a good seal that never dries out.

[mcgarrett]

ford38v8 is correct on both points above.

[chuck stevens]

Fuel pumps, mechanical or electric, only pump liquids. The new gas has methanal witch boils easier than the old gas, as low as 95 degrees. Check the tail pipe, and muffler area to see how close to the gas line they are. New cars with fuel injection return hot fuel to the gas tank to be cooled. Rebuilding the carb and fuel pump WILL NOT SOLVE your problem. By the way Charlie is the best.

[Bill OH]

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I have not had any problems with my copper fuel line, which was installed in 1988.I have removed steel lines from Fords - rusty and had holes.

Used neoprene gaskets on the fuel filters on farm tractors for years and the gaskets did not get hard - used the same gasket continuously as I have done on my Ford fuel pump since 1988.

[Lawson Cox]

Originally Posted by mcgarrett

Let's start by checking a couple of things...could be defective fuel pump diaphragm or power valve. Depending on how old they are, I would consider replacing them. At least you've taken a couple of potentially troublesome items off the table.

That's make work. Before replacing them, check to see if they are the problem. Easy Peasy.

[Pech33]

If you go to an electric fuel pump, you have to adjust the fuel pressure with a regulator. I believe 3 lbs of pressure is the recommendation. My pump is a 5-8 lb unit that was cranking 8lbs of pressure into my Model 94. All kinds of issues (flooding, fouled plugs, etc).

[Mountain Dew]

Originally Posted by Lawson Cox

That's make work. Before replacing them, check to see if they are the problem. Easy Peasy.

I think I know how to check for cracks in the fuel pump diaphragm but how do you test the power valve?

[ford38v8]

Originally Posted by Mountain Dew

I think I know how to check for cracks in the fuel pump diaphragm but how do you test the power valve?

Remove it from the carb. The valve will stick to your tongue with suction in one direction.

[Mountain Dew]

I checked the cork gasket in the sediment bowl. It fell apart. I happened to have a neoprene replacement. We'll see how it goes.

[Mountain Dew]

I let the car sit for 5 days. The fuel level in the sediment bowl was full. I choked it and she started right up. I'll continue to monitor the situation.

[ford38v8]

Originally Posted by Mountain Dew

I let the car sit for 5 days. The fuel level in the sediment bowl was full. I choked it and she started right up. I'll continue to monitor the situation.

Which sediment bowl? You have 3. It's really the float bowl that you monitor, not the sediment bowl.

[Mountain Dew]

The sediment bowl on the fuel pump.

[ford38v8]

Originally Posted by Mountain Dew

The sediment bowl on the fuel pump.

That tells you nothing about the condition of the carburetor. The float bowl is under the air horn. That is where you watch the fuel level.

[tubman]

Originally Posted by ford38v8

That tells you nothing about the condition of the carburetor. The float bowl is under the air horn. That is where you watch the fuel level.

See posts 31 and 32.