Fuel ????

[Gezer]

my 40 ford sedan with a 53 EAB truck flathead has to be cranked for a long time before there is gas in the Once there it seems to run all right.
A clear tube style fuel filter is in line about a foot from the stock fuel pump.

How would one trouble shoot . I do not see fuel on the floor or engine.

[corvette8n]

It’s probably running out of the float bowl into the motor while it sit for a while.
Have the carb rebuilt, I recommend CharlieNY.
You can also install an inline fuel pump, I have one on my car with a switch that I turn on for about 30 seconds to fill the bowl in the carb.

To trouble shoot pull the top off the carb of to see if there is fuel in the bowl.

[drolston]

Either the fuel pump itself is degrading or suffering from a restriction or vacuum leak on the pump input side.
- Once you have fuel to the carb so that the engine will start, shut it down. Disconnect the fuel line from the carb and WITH THE IGNITION OFF, use a helper or remote starter button to crank the engine. With each revolution of the cam the pump should spurt about a tablespoon from the fuel line.
- If the pump puts out the expected amount, I suspect the problem may be the fuel bowl in the carb leaking down rapidly, between runs. If your carb is a 94, suspect a leaking power valve.
- If that checks out okay, look for a vacuum leak on the pump; usually the gasket sealing the top of the fuel bowl; maybe tighten down the screws holding the top of the fuel pump to the bottom.
- If the fuel pump output was weak, check for the vacuum leaks and then check for restrictions, like a clogged fuel filter or swollen/collapsed flexible fuel line at the firewall.

Let us know if these measures do not find your problem.

[62pan]

It could be as simple as the fuel evaporating. It seems the newer fuel evaporates a lot faster these days. I had the same issue and found a few threads on the subject all talking how fast there carbs were loosing fuel. In a week times the fuel bowl on my roadster was almost dry. I installed a inline pump to fill the carbs before starting. No issues since.

[aussie merc]

yes ethanol based fuel mix's do evaporate quicker than gasoline as they where not designed to work with carbs but sealed injection systems they also have next to no shelf life about 2 weeks then they degrade [its due to the alcohol in the mix ] priming pumps help overcome this but your fuel pump may be loosing suction and be in need of a rebuild with E proof components Alcohol its self is not a bad fuel but you must have the correct parts as it was widely use in industry as a solvent due to its zero residue properties

[Crankster]

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I don't believe it is an ethanol issue. It probably doesn't help any, but the reason I say that is many people avoid its use altogether esp. in classic or collector cars, and yet still run into the exact same problem with only straight unadulterated gasoline. The vapor pressure standards, the blends that refineries produce for automotive use are a lot different today, carburetors long ago made obsolete. What I observed is some carburetor types are much more prone to this problem than others.

It won't necessarily be a situation where the carburetor is completely dry, there can be plenty of fuel in the bowl. The problem it seems to me, is that the "light ends" or especially volatile portions of the fuel - contained in that small portion by volume in the fuel bowl itself responsible for engine starts - the components in that which aid in quick reliable starts evaporates or boils off, and the remainder while sufficient in volume, just isn't very hot.

To avoid extended wear and tear on starter and battery I've taken to "priming" the carburetor with a shot of fresh fuel down the carb throat if the engine hasn't been started in a while.

[Flathead Fever]

Years ago, I inherited an original low mileage '57 T-bird that had belonged to my grandfather. As long as you drove it once a week it was fine but if it sat for two weeks and the carb dried out you could crank it until the battery died and it would not fill up the factory Holley 4V's carb bowl. It still used of those cloth covered fuel hoses from the firewall to the fuel pump. My grandfather had bought every NOS part from Ford he thought he would ever need. All the small rubber parts were sealed in peanut butter jars for over twenty-years. In one jar was a brand-new fuel hose with its Ford part number on it, it was flexible, it looked new. I stuck it on the T-bird, and it didn't help the problem. I took it back off and took it to the kitchen sink, covered it in dish soap and blew on it. Bubbles came out of that cloth covering from one end to the other. It looked new on the outside, but the cloth covering was hiding cracks in the rubber. I would think that with cracks in the rubber you would have seen or smelled fuel, but I never did.

In their day, old cars were driven constantly so the fuel in the carbs never had a chance to evaporate. Its a good idea just to go out in the garage and start these cars once a week. Also, Stomp on the brake pedal to put some residual pressure into system.

If the carb does go dry a healthy fuel system should be able to fill the carb bowl without cranking the engine until the battery dies. Back when fuel did not have ethanol fuel pump diaphragms, rubber fuel lines and carb parts still only lasted about ten years so its not a bad idea to just replace all the rubber in a fuel system if its been longer then ten-years

Stick a vacuum gauge on the inlet side of the pump and see if it is pulling the specified vacuum. Then go back to the tank and disconnect the line and see if it pulls the same vacuum there. It worked at one time so it's not design, something has changed, most likely a tiny vacuum leak.

[Crankster]

"Something has changed"

Yes! Gasoline. Since the advent of electronic fuel injection, the refiners don't need to worry about vapor lock. It's an index or specification called Reid Vapor Pressure. Modern fuel tanks are completely sealed, lines, everything. Carburetors were generally open to the atmosphere.

[Flathead Fever]

Originally Posted by Crankster

"Something has changed"

Yes! Gasoline. Since the advent of electronic fuel injection, the refiners don't need to worry about vapor lock. It's an index or specification called Reid Vapor Pressure. Modern fuel tanks are completely sealed, lines, everything. Carburetors were generally open to the atmosphere.

Fuel injection cured vapor lock. Since the fuel is under such high pressure 15 to 50 lbs., from the pump inside the tank to the injector it cannot turn to a vapor. Pressure raises the boiling point, that is why we use pressurized cooling systems. Also, with the pump mounted inside a tank of fuel it helps keep the pump cool.

With a mechanical fuel pump, the inlet side is pulling a vacuum on the fuel which lowers its boiling point inside the fuel lines which can cause the fuel to turn to a vapor (vapor lock) Especially on a hot day using low octane fuel, fuel lines routed close to the exhaust and even high altitudes.

On the outlet side of the pump between the pump and the carb the fuel is under pressure which raises its boiling point which helps prevent vapor lock with the high under hood temperatures. With a flathead fuel pump having such a low output pressure vapor lock might have been a more common problem than it was in later years when carbureted vehicles fuel pumps had an output pressure around 5 to 6 lbs. It might have also been common in the 1920-1940s when fuel was engineered for low compression engines.

I'll give you an example of what just one less pound of fuel pressure did. Where I worked at, the phone company, our fleet had about a dozen 1984, carbureted, Chevy Suburbans that were quitting up in the mountains (5000' to 8000' elevation). It always happened on very hot days. We would bring them down off the mountain to work on them and we could never duplicate the problem at 1000' elevation. The problem turned out to be the mechanical fuel pumps, as they got older their pressure output reduced from 5 to 6 pounds down to 4 pounds. They worked fine down in the valley with 4 lbs of pressure. For every 1000' of elevation you go up the atmospheric pressure drops one-pound so the fuel will vaporize at a lower temperature up in the mountains. With only four pounds of pressure on the fuel between the pump and the carb, and on hot days, with hot under hood temperatures the fuel must have been turning to vapor between the pump and the carb. The 4-pound pressure reading was taken inside the shop at the 1000' elevation, I imagine if I had checked it at a 5000' elevation, I would have gotten a lower pressure reading. The drivers figured out that when quit running to pour water on the fuel pump and fuel line and then they could on their way again. Pulling the fuel line and testing to see if the pump was squirting fuel would have lead you to believe the pump was fine when it wasn't.

Hardly anybody ever checks the vacuum and pressure on a mechanical fuel pump. They pull the hose and make sure its pumping, and that's usually a good enough test but when your having an intermittent problem kicking your butt its time to get out the testers and make sure your parts are within specifications.

[Crankster]

This is true, but that was my point. When we use carbureted systems, with the new and improved fuel, there can be problems with evaporation, that wasn't nearly as much of a factor with the old school pump gas.

There are actually a few tests for a mechanical fuel pump when checking them by the book! Pressure, volume, and "suction" on the inlet side. Interesting observation about altitude and the effects of vapor lock.

[Gezer]

Turns out the carb was one for a newer engine. I bought a new carb from Charlie Price in Florida. A Holly(Ford)
I need the adjust the idle mix. Is there a written, how to, on setting up this carb? Where do I attach the Vac Gauge to get max setting?

Thanks, Need all the help I can get

[A bones]

For reasons that apply and for reasons other than this, I will say that the filter you describe is not desirable. Please R & R it with a plastic cartridge type, like you would find on an 'ordinary' car . Best Wishes

[Charlie ny]

Gez,
Warm the motor up, back both needles out 1 1/2 turns. Slowly turn one needle

in until the motor motor lags or runs slightly rough back that needle out 1/2 turn.

Follow the same procedure with the other needle. The catb is in the ball park
adjustment wise. Now WITHOUT backing the needles out turn each one in until the
motor lags and turn out 1/2 turn...........you'll be as close as you'll ever need to be
providing the carb is in good shape.
Charlie ny

[aussie merc]

Gezer disconnect the wiper hose and plug in there i have an AN fitting in my manifold that i use [fitted by yours truely] or next time you have the carb off refit with a drilled under spacer from the dreaded EBAY they arent expensive